MATERIALS and MOLECULAR RESEARCH DIVISION Annual Report 1982

LBL-I5150

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Thit report was prepared si an account of work sponsored by an ageacy of the United States Government. Neither the United States Government nor aay agency thereof, aor any of their LBL--15150 employees, makes any warranty, express or implied, or assumes aay legal liability or respotat- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that fts use would not infringe privately owned rights. Refer DE83 015005 ence herein to any specific- commercial product, process, or service by trade name, tradcaaark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom mendation, or favoring by the United States Government or aay agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

MATERIALS AND MOLECULAR RESEARCH DIVISION

Annual Report 1982

May 1983

Alan w. Searcy, Division-Head Rolf H. Muller, Asst. Division Head for Research Conway V. Peterson. Asst. Division Head for Administration

Lawrence Berkeley Laboratory University of California Berkeley, California 94720 mm

msimroran nr THIS Mwetr IS m\wmi % I Materials Sciences

II Chemical Sciences I III Nuclear Sciences I IV Fossil Energy I V Advanced Isotope Separation Technology I VI Energy Storage I VII Magnetic Fusion Energy I VIII Nuclear Waste Management I IX Work for Others I X Appendices I V

Contents

GENERAL INTRODUCTION xxiii

I. MATERIALS SCIENCES A. Metallurgy and Ceramics 1. Structure of Materials a. Structure and Properties of Transformation Interfaces Ronald Gronsky, Investigator 1. Grain Boundaries in Body-Centered Cubic Metals 1 2. Grain Boundaries and Interfaces in Semiconductors . 2 3. Transformation Interfaces in Aluminum Alloys 2 1982 Publications ano Reports 3

b. Microstructure, Properties, Alloy Design: Inorganic Materials Gareth Thomas- Investigator A. Alloy Design: Medium Carbon Steels 1. Characterization of the Effects of Laser Heat-Treatment Upon the Microstructure and Mechanical Properties of Fe/3Cr/2Mn/0.5Mo/0.3C 4 2. Mechanical Properties and Microstructure of Lower Bsinite in a 0.3»C-3%Cr-2^Mn Steel 5 3. The Nature and Origin of Sliding Wear Debris from Steels 5 4. Fundamentals of Abrasive Wear 6 B. Alloy Design: Low-Carbon Dual Phase Steels 1. Design of High Strength Dual-Phase Steel Wire G C. Magnetic Materials 1. EM Study of CaO Segregation at the Grain Boundaries in (Mn,Zn)Fe 0 7 2. Development 2of4 the Cellular Microstructure in the SmCo7 4-Type Magnets .. 8 3. Electront Microscopy of Mn-Al Magnets B 4. Annealing of High Permeability (Mn,Zn)Fe204 9 1982 Publications and Reports 9

c. Solid State Phase Transformation Mechanisms Kenneth H. Westmacott, Investigator 1. Precipitation in the Pt-C System 11 '. Ledge Structure and Precipitate Growth in Al-Cu 11 3. The Relationship Between Invariant Line Strain and Precipitate Needle Growth 11 4. M02C Precipitate Structure and Morphology in Molybdenum 12 5. Work in Progress 13 1982 Publications and Reports 13 VI d. National Center for Electron Microscopy Gareth Thomas, Ronald Gronsky, and Kenneth H. Westmacott, Investigators 1. 1.5 MeV High Voltage Electron Microscope 14 2. Atomic Resolution Microscope 19 3. Periodic Extension in Optical Diffraction Analysis . . , 20 4. Real '"pace Image Sirrjlatiou in High Resolution Microscopy 20 5. Characterization of A1N Ceramics Containing Long Period Polytypoids •- 21 1982 Publications and Reports 21 e. In-Situ Investigations of Gas-Solid Reactions by Electron Microscopy James W. Evans and Kenneth H. Westmacott, Investigators 1. Tne Microstructure and Reactivity of Metal Oxides 22 1982 Publications and Reports 24 f. Local Atomic Configurations in Solid Solutions Oidier de Fontaine, Investigator 1. Long-Period Superstructures 25 2. YTT Diagrams , 25 1982 Publications and Reports , 26

Mechanical Properties a. Theoretical Problems in Alloy Design John W. Morris, Jr., Investigator 1. The Linear Elastic Theory of Phase Transformations in Sends 27 2. Dislocation Motion at Low Temperature 27 3. Microstructural Sources of the Ductile-To-Brittle Transition in Steel 28 4. The Coupling Between Magnetic- and Deformation-Induced Martensite in Metastable Austenitic Steels 29 5. Mossbauer Spectrometry 29 6. The Metallurgy of Fe-Mn Steels 29 7. High Temperature Embrittlenent of an Iron-Based Superalloy ...... 30 8. Micros' ucture Control During Welding of Ferritic Steels 30 9. SuperaVoy Welding . 30 10. The Use of Heat Treatment to Improve the Critical Current of Bronze-Process Multifilamentary Superconducting Wire 31 11. The Influence of Magnesium Additions on the Properties of Multifilamentary Nb3Sn Superconducting Wire 31 3982 Publications and Reports 32 b. Mechanical Properties of Ceramics Anthony G. Evans, Investigator High Temperature Failure 1. High Temperature Failure Initiation in Liquid Phase Sintered Materials 34 2. A Damage Model of Creep Crack Growth in Poiycrystals 34 3. High Crack Growth in Polycrystalline Alumina 35 4. The Influence of Inhomogeneities on High Temperature Failure in Ceramics 35 Sintering 1. Microstructure Evolution During Sintering: The Role of Evaporation/Condensation , 36 vi i

2. An Experimental Assessment of Pore Breakaway During Sintering 36 3. Initial Stage Sintering with Coupled Grain Boundary and Surface Diffusion 37 1982 Publications and Reports 37

c. Environmentally Affected Crack Growth in Engineering Materials Robert 0. Ritchie, Investigator 1. On the Load Ratio Dependence of Fatigue Thresholds 39 2. Influence of Viscous Environments on Fatigue Crack Growth 40 3. Fatigue Resistant Microstructures in Dual-Phase Steels 40 4. Mechanisms of Fatigue Crack Growth Under Variable Amplitude Loading 40 1982 Publications and Reports 40

3. Physical Properties a. Interfaces and Ceramic Microstructures Joseph A. Pask, Investigator 1. wetting and Reactions in the Lead Borosilicate Glass-Precious Metal Systems 43 2. The Silica-Alumina System 43 1982 Publications and Reports M

b. High Temperature Reactions Alan W. Searcy, Investigator 1. The Equilibrium Shapes of Crystals and of Cavities in Crystals 45 2. Effects of Particle Size and Powder Bed Size on Calcite Decomposition Rates 45 3. Possible Metastability of MgO Resulting From the Decomposition

of Mg(0H)2 46 4. Confirmation of Bimodal Pore Size Distribution in CaO from Calcite Decomposition 47 5. Gas Flow Through Porous Barriers: The O^-Pt, CO-Pt Systems 47 1982 Publications and Reports 48

c. Structure-Property Relationships in Semiconductor Materials Jack Washburn, Investigator 1. The Mechanism of Degradation of CujS-CdS Solar Cells as Revealed by High Resolution Electron Microscopy 49 2. An Application of High Resolution Lattice Imaging Electron Microscopy to a Study of the Mechanism of the Crystalline to Amorphous Transformation 49 3. Effect of Recoil Implanted Oxygen on the Development of Secondary Defects in MOS Test Wafers 50 4. In-Situ Observations of MeV Electron Beam Induced Crystal Growth into an Amorphous Layer in Silicon 50 5. Effect of Temperature and Displacement Damage on the Growth of Amorphous Layers in Silicon . 50 6. A Model for Redistribution of Phosphorus During Annealing of High Dose Ion Implanted Silicon 51 7. Diffraction Extinction Conditions for Silicon and Other Materials with Diamond Glide Planes 51

1982 Publications and Reports r_ viit

d. Chemical Properties and Processing of Refractory Ceramics Lutgard C. De Jonghe, Investigator 1. Processing of Ceramics ..... 53 2. Structure and Nonstoichiometry of Calcium Aluminates 53 3. Work in Progress 55 1982 Publications and Reports 55

e. Structure and Electrical Properties of Composite Materials Robert H. Bragg, Investigator 2. Density of Heat-Treated GC , . . . 56 2. Pore Growth in Glassy Carbon 57 3. Work in Progress 57 1982 Publications and Reports 57

f. High Temperature Oxidation and Corrosion of Materials David P. Whittle, Investigator 1. Mechanism of Peg Growth and Influence on Scale Adhesion 58 2. Microstructure and Growth of Protective CrgO^ and AI2O3 Scales at High Temperature 59 3. The Influence of Alloy Microstructure on AI2O3 Peg Morphologies in CoCrAl Alloys and Coatings 60 4. Sulfur Diffusion in Oxide Grain Boundaries .... 60 5. The Effects of SO2 and SO3 on the Na2S04 Induced Corrosion of Nickel 61 6. Effects or Chlorides on NagSO^Induced Hot Corrosion c" *CrAl 61 7. Multiphase Diffusional Growth During Aluminizing 62 8. High Temperature Oxidation of Ni-Co Alloy . 62 1982 Publications and Reports 63

g. Ceramic Interfaces Andreas M. Glaeser, Investigator 1. Grain Boundary Mobility Measurements in MgO-Doped AI2O3 ... 64 1982 Publications and Reports 65 4. Engineering Materials a. Abrasive, Erosive, and Sliding Wear of Materials Iain Finnie, Investigator 1. Sliding Wear of Dissimilar Metals . 66 2. Abrasive Wear 66 3. An Overview of Wear . 66 1982 Publications and Reports 67

b. Erosion-Corrosion Wear Program Alan V. Levy, Investigator 2. Measurement and Numerical Modeling of Two Phase Flew 68 2. Measurements of Air Flow in a Curved Pipe Using Laser-Doppler Velocimetry ... 68 3. Particle Flow Characteristics Determination in Gas and * Liquid-Solid Particle Streams 68

1982 Publications and Reports l; 69 ix

c. Erosion of Brittle Solids Anthony G. Evans, Investigator 1. The Mechanical Behavior of Brittle Coatings and Layers 70 2. Measurements of Dynamic Hardness by a Controlled Impact Technique 71 1982 Publications and Reports 71

d. Chemical Degradation of Refractories David P. Whittle, Investigator 1. High Temperature Degradation of Refractories in Mixed Gas Environments 72

5. Experimental Research

a. Far Infrared Spectroscopy Paul L. Richards, Investigator 1. Infrared Emission Spectroscopy of CO on Ni 73 2. Low Temperature Infrared Absorption Spectroscopy of CO on Ni 74 3. Far Infrared Optical Properties of an Organic Superconductor 74 4. Work in Progress 74

1982 Publications and Reports 75

b. Experimental Solid State Physics and Quantum Electronics Yuen-Ron Shen, Investigator 1. Spectroscopy of Molecular Monolayers by Resonant Second-Harmonic Generation 77 2. Transient Four-Wave Mixing and Coherent Transient Optical Phenomena 78 3. Nonlinear Wave Interaction Involving Surface Polaritons 79 4. Surface-Enhanced Second-Harmonic Generation and Raman Scattering 79

1982 Publications and Reports 79

c. Excitations in Solids Carson D, Jeffries, Investigator 1. Period Doubling and Universal Chaotic Behavior in P-N Junctions in Silicon 82 2. Intermittency Route to Chaos 83 3. Period Doubling and Chaos in Spin Wave Instabilities in Yttrium Iron Garnet 83 1982 Publications and Reports 84

d. Time-P^solved Spectroscopies in Solids Peter Y, Yu, Investigator 1. Nonequilibrium Phonon Spectroscopy in GaAs 85 2. Lifetime of Ortho-Exciton and Ortho- to Para-Exciton Conversion in CujO 85 1982 Publications and Reports 85

e. Superconductivity, Superconducting Devices, and 1/f Noise John Clarke, Investigator 1. Chaos in Josephson Junctions 87 2. Measurements of Current Noise in DC SQUIDs 88 X

3. Correlation Lengths in Magnetotellurics 88

1982 Publications and Reports 89

6. Theoretical Research

a. Theoretical Studies of the Electronic Properties of Solid Surfaces Leo M. Falicov, Investigator 1. Magnetic and Electronic Properties of Ni Films, Surfaces, and Interfaces , 91 2. Thermodynamic Properties of Li Intercalated and Disordered Layer Compounds 92

1982 Publications and Reports 92

b. Theoretical Solid State Physics Marvin L. Cohen, Investigator 1. Solid Surfaces 94 2. Crystal Structure 94 3. Lattice Dynamics 94 4. Electronic Structure , 95 5. Work in Progress 95

1982 Publications and Reports 95

7. Chemical Structure

a. Low Temperature Properties of Materials Norman E. Phillips, Investigator 1. Absolute Temperature Determinations in the mK Region 97 2. The Specific Heat of ^He in the Fermi Liquid Region 97 3. Low-Temperature Specific Heat of Potassium 98 4. Observation of the Spin Glass-Paramagnet Phase Boundary 98

1982 Publications and Reports 98

b. Electrochemical Processes Charles W. Tobias, Investigator 1. Anodic Processes in Propylene Carbonate 100 2. Work in Progress 101 1982 Publications and Reports 101

8. High Temperature and Surface Chemistry a. High Temperature Thermodynamics Leo Brewer, Investigator 1. Use of Gaseous-Condensed Phase Equilibration to Determine Thermodynamic Quantities for Very Stable Transition Metal Alloys 103 2. High Temperature EMF Measurements 104

1982 Publications and Reports 104

b. Chemistry and Materials Problems in Energy Production Technologies D. R. Olander, Investigator 1. The UO2 - Zircaloy Chemical Interaction 106 2. Investigation of Iron-Chlorine Reaction by Modulated Molecular Beam Mass Spectrometry 107 3. A Thermodynamic Assessment of In-Reactor Iodine SCC of Zi'rcaloy 107 4. Multiphoton Laser Ionization Mass Spectrometry of Csl and I 107 5. The Kinetics of Gas/Sol id/Liquid Reactions by Nodulated Molecular Beam Mass Spectrometry 10B

1982 Publications and Reports . 108

Plasma Enhanced Deposition of Thin Films Dennis W. Hess, Investigator

1. Plasma-Deposited Titanium Oxide Photoanodes 110 2. Structure and Photoelectrochemical Properties of Plasma-Deposited Iron Oxide Films 110 1982 Publications and Reports 110

Electrochemical Phase Boundaries Rolf H. Muller, Investigator

1. Nucleation of Pb Electrodeposits on Ag and Cu 112 2. Effect of Rhodamine-B on Pb Electrodeposition on Ag and Cu 112 3. Self-Compensating Spectroscopic Ellipsometer . 113 4. Work in Progress

1982 Publications and Reports 113

Solid State and Surface Reactions Gabor A. Somorjai, Investigator

Su-face Structure and Chemisorption by Low Energy Electron Diffraction and Electron Spectroscopy

1. A LEED Crystallography Study of the (2x2)-C?H3 Structure Obtained After Ethylene Adsorption on Rh(lll) 115 2. Evidence for the Formation of Stable Alkylidyne Structures From C3 and C4 Unsaturated Hydrocarbons Adsorbed on the Ptjlll) Single Crystal Surface 115 3. Force-Field Calculations of the Packing Energy of Monolayers of C3 and C4 Hydrocarbon Molecules Adsorbed on Single Crystal Metal Surfaces 115 4. Vibrational Studies of Alkene Decomposition on the Rh(lll) Surface 116 5. A Covalent Model for the Bonding of Adsorbed Hydrocarbon Fragments on the (111) Face of Platinum 116 6. The Adsorption of Benzene and Naphthalene on the Rh(lll) Surface: A LEED, AES, and TDS Study 116 7. Vibrational Spectroscopy Using HREELS of Benzene Adsorbed on the Rh(lll) Crystal Surface 116 8. The Structure of Graphitic Carbon on Pt!lll) 117 9. The Coadsorption of Potassium and CO on the Pt(lll) Crystal Surface: A TDS, HREELS, and UPS Study 117 10. The Interaction of Potassium with ir-Electron Orbital Containing Molecules on Pt(lll) 117 11. The Characterization of Pt/Cu Alloy ant! Epitaxial Surfaces 117 12. A New Model for CO Ordering at High Coverages on Low Index Metal Surfaces: A Correlation Between LEED, HREELS, and IRS. CO Adsorbed on fee (100) Surfaces 118 13. LEED Intensity Analysis of the (1 x 5) Reconstruction of Ir(100) 118 14. The Adsorption and Binding of Thiophene, Butene, and H2S on the Basal Plane of M0S2 Single Crystals 118 15. LEED and AES Study of Zirconium Overlayers on the Pt(100) Crystal Face 118

Studies of Catalyzed Surface Reactions 1. Ammonia Synthesis Catalyzed by Rhenium 119 X11

2. Interaction of CO, CO2, and Dj with Rhodium Oxide: Its Reduction and Catalytic Stability ..... 119 3. Deuterium Isotope Effects for Hydrocarbon Reactions Catalyzed Over Platinum Single Crystal Surfaces 119 4. Studies of Sulfur Monolayers on Mo(lOO) and Its Effects on Adsorbate Binding 119 5. The Effect of Potassium on the Catalyzed Reactions of n-Hexane Over Pt(lll) and Pt-[6(lll)x(lll)] Single Crystal Surfaces 119 6. Dehydrogenation of Cyclohexane Catalyzed by Bimetallic Au-Pt Single Crystal Surfaces 120 7. Energy Redistribution Among Internal States of Nitric Oxide Molecules Upon Scattering From Pt(lll) Crystal Surface 120 1982 Publications and Reports . . 120

f. Nuclear Magnetic Resonance Alexander Pines, Investigator 1. Broadband Population Inversion 124 2. Time-Resolved Optical Nuclear Polarization 124 3. Zero Field NMR 124 4. Anisotropic Diffusion in Oriented Systems 125 5. High Resolution NMR of Feldspars and Zeolites 125 6. Theory of Spin Diffusion in Solids 125 7. Time-Resolved CIDNP and Magnetic Isotope Effect 125 8. Molecular Conformation in Liquid Crystals 125 9. Excitation of High N-Quantum Transitions 126

1982 Publications and Reports 126

II. CHEMICAL SCIENCES A. Fundamental Interactions 1. Photochemical and Radiation Sciences

a. Photon-Assisted Surface Reactions, Materials, and Mechanisms Gabor A. Somorjai, Investigator 1. Photocatalytic Production of Hydrogen from Water by a p- and n-Type Polycrystalline Iron Oxide Assembly „ 129 2. The Preparation and Selected Properties of Mg-Doped p-Type Iron Oxide as a Photocathode for the Photoelectrolysis of Water Using Visible Light 129 3. Work in Progress 129

1982 Publications and Reports 130

b. Photochemistry of Materials in the Stratosphere Harold S. Johnston, Investigator 1. The Reaction of Chlorine Atoms with Nitric Acid Vapor 131 2. Temperature-Dependent Ultraviolet Absorption Spectrum of Di-Nitrogen Pentoxide 131 3. Work in Progress 132

1982 Publications and Reports . 132

2. Chemical Physics a. Energy Transfer and Structural Studies of Molecules on Surfaces Charles B. Harris, Investigator

1. Enhanced Photochemistry on Metal Surfaces 133 2. Electronic Energy Transfer to Semiconductor Surfaces 133 3. Vibrational Coherence and Picosecond Studies in Liquids . . 134 1982 Publications and Reports 134 b. Molecular Beam Spectroscopy John S. Winn, Investigator 1. Dissociation Mechanisms of Metal CarbonyIs 136 2. Supersonic Molecular Beam Relaxation Mechanisms .... 136 1982 Publications and Reports 137

c. Selective Photochemistry C. Bradley Moore, Investigator 1. Absolute Rate Constants for the Removal of CHg (*Ai) 138 2. High Vibrational Overtone Photochemistry 139 1982 Publications and Reports 140

d. Physical Chemistry with Emphasis on Thermodynamic Properties Kenneth 5. Pitzer, Investigator 1. Relativistic Ab Initio Molecular Structure Calculations Including Configuration Interaction with Application to Six States of T1H 141 2. Electron Structure Calculations Including CI for Ten Low Lying States of Pb2 and Sn2- Partition Function and Dissociation Energy of Sn? 141 3. Nuclear Spin Statistics of Cubane and Icosahedral Borohydride Ions 142 1982 Publications and Reports 142

e. Molecular Interactions William A. Lester, Jr., Investigator 1. Theoretical Study of Elementary Reactions in Combustion Processes 144 2. Theory of Polyatomic Phctodissociation . . 145 3. Fixed-Node Quantum Monte Carlo for Molecules 146 4. Work in Progress 146 1982 Publications and Reports 146

f. Theory of Atomic and Molecular Collision Processes Williair H. Miller, Investigator 1. Dynamical Models for Polyatomic Reaction Dynamics 148 2. Dynamical Effects of Reaction Path Symmetry; Mode-Specificity in the Unimolecular Dissociation of Formaldehyde 148 1982 Publications and Reports 149 q. Photoelectron Spectroscopy David A. Shirley, Investigator 1. Direct Surface Structure Determination with Photoelectron Diffraction lbi 2. High Resolution Fourier Analysis with Auto-Regressive Linear Prediction 151 3. Normal Photoelectron Oiffraction of fVCu(OOl): A Surface Structural Determination 152 4. The Two-Dimensional Valence Electronic Structure of a Monolayer of Ag on Cu(OOl) 152 5. The evolution to Three-Dimensional Valence Band Structure in Ag Overlayers on Cu(OOl) 153 6. High Resolution Angle-Resolved Photor.mission Study of the Valence Band Structure of Ag(lll) 154 XIV

7. Construction of a High Resolution Electron Energy Loss Spectrometer . «... 154 8. Threshold Measurements of the K-Shel! Photoeiectron Satellites in He and Ar 155 9. Photoeiectron Measurements of the Mercury 4f, 5p, and 5d Subshells 155 10. Photoionization of Helium to He+(n«2): Autoionization and Final-State Symmetry 156 11. Photoeiectron Angular Distributions of the NjO Outer Valence Orbitals in the 19-31 eV Photon Energy Range 156 12. Rotationally Resolved Photoeiectron Angul£r Distributions for Hj (V.0) at 1 . 584 A and 736 A 157 13. Rotational Relaxation in Supersonic Peams of Hydrogen by High Resolution Photoeiectron Spectroscopy 157 1982 Publications and Reports 153 h. Crossej Molecular Beams Yuan T. Lee, Investigator 1. O^D) + HD Reactive Scattering 160 2. Photoexcitation Studies of Substituted Cyclohaptatrienes . . 160 3. Photochemistry of Glyoxal 161 4. Elastic Scattering of ArXe .-.nd KrXe . 162 5. Photodissociation of Large Water Clusters 162 6. Infrared Multipholo>! Dissociation of C7F5CL and C^Br 162 7. Molecular Beam Studies of Vibrational Predissociation of (CjHa^ and (10)3)2 Using a Pulsed CO2 Laser 163

1982 Publications and Reports 163 i. Potential Energy Surfaces for Chemical Reactions Henry F. Schaefer III, Investigator

1. Terminal vs 8ridge Bonding of Methylene to Metal Systems AI2CH2 as a Model System 166 2. The Weakly Exothermic Rearrangement of Methoxy Radical (CH3OO to the Hydroxymethyl Radical (CHjOH-) 167 3. Cyclic DJI, Hexaazaoenzene—A Relative Minimum on the N6 Potential Energy Hypersurface 167

1982 Publications and Reports 168

Atomic Physics a. Atomic Physics Richard Marrus, Investigator 1. Parity Violation in Atoms 170 2. One Percent Measurement of the Lifetime of the 2 2Si/2 State of Hydrogenlike Argon (Z = 18) 170 3. Electron Capture by Low-Energy Multicharged Neon Ions 171

1982 Publications and Reports 171

Chemical Energy a. Formation of Oxyacids of Sulfur from SO2 Robert E. Connick, Investigator

1. The Rate and Mechanism of Exchange of Oxygens Between Bisulfite Ion and Water 172 2. Rates of Substitution Reactions on Metal Ions ..... 172 1932 Publications and Reports 172 Catalytic Hydrogenation of CO: Catalysis on Well-Characterized Surfaces Gabor A. Somorjai, Investigator and Catalysis by Supported Metals Alexis T. Bell, Investigator

1. The Hydrogenation of CO Over Rhodium Foil, and Rhodium Compounds, FeRhOs and Na2Rh03 173 2. The Effects of Additives en the Fe and Re Catalyzed CO Hydrogenation Reactions 173 3. The Production of Methanol from CO and H2 Over Thorium Oxide Catalyst Surfaces . !' 174 4. Characterization of Carbon Deposits Formed During CO Hydrogenation Over Ruthenium ... 174 5. The Influence of Metal-Support Interactions on the Synthesis of Methanol Over Palladium 174

2982 Publications and Reports . , 174

Organometallic Chemistry of Coal Conversion K. Peter Vollhardt, Investigator

1. Biscarbyne Clusters as Homogeneous Analogs of Fischer-Tropsch Intermediates on Surfaces 176- 2. Transition Metal Mediated Thermal Extrusion of Sulfur Dioxide from Thiophene-1,1 Dioxides 176 3. Work in Progress 177

1982 Publications and Reports 177

Synthetic and Physical Chemistry William L. Jolly, Investigator

1. An X-Ray Photoelectron Spectroscopic Study of the a- and Tt-Allyl Groups 179 2. An X-Ray Photoelectron Spectroscopic Study of the Bonding in (Alkylidyne) Tricobalt Nonacarbonyl Complexes and Related Compounds 179 3. An X-Ray Photoele^tron Spectroscopy Study of Transition Metal v-Methylene Complexes and Related Compounds . , 179 4. Justificstion of the Approximation That Shifts in Nonbonding Valence Orbital Ionization Potential are Eight-Tenths of Shifts in Core Binding Energy 179 5. Work in Progress 180

1982 Publications and Reports 180

Chemistry and Morphology of Coal Liquefaction Heinz Heinemann, Investigator, with Alexis T. Bell, James W. Evans, Richard H. Fish, Alan V. Levy, Eugene E. Petersen, Gabor A. Somorjai, Theodore Vermeulen, and K. Peter Vollhardt, Investigators

[See Fossil Energy Section]

Electrochemical Systems John Newman, Investigator

1. Mathematical Modeling and Optimization of Liquid-Junction Photovoltaic Cells 181 2. Electrochemical Removal of Mercury from Contaminated Brine Solutions 182

1982 Publications and Reports 182 xvl

g. Surface Chemistry—Application of Coordination Principles Earl L. Muetterties, Investigator 1982 Publications and Reports . 183

h. High-Energy Oxiders and Cslocalized-Electron Solids Neil Bartlett, Investigator 1. An Electrechemically Reversible Intercalation of Graphite by Fluorine in the Presence of Hydrogen Fluoride 185 2. A Thermodynamic Threshold for the Intercalation of Graphite by Hexafluorospecies MF5- 186 3. Intercalation of Graphite by Silicon Tetrafluoride and Fluorine to Yield a Second-Stage Salt C24S1F5. 186 1982 Publications and Reports 187

i. Transition Metal Catalyzed Conversion of CO, NO, Hj, and Organic Molecules to Fuels and Petrochemicals Robert G. Bergman, Investigator 1. Activation of C-H Bonds in Saturated Hydrocarbons on Photolysis of (n5-C5Me5)(PMe3)IrH . Relative Rates of Reaction of the Intermediate with 2 Different Types of C-H Bonds, and Functionalization of the Metal-Bound Alkyl Groups 188 2. Work in Progress 189 1982 Publications and Reports 189

Chemical Engineering Sciences a. High-Pressure Phase Equilibria in Hydrocarbon-Water (Brine) Systems John M. Prausnitz, Investigator 1. Experimental High-Pressure Vapor-Liquid Equilibrium 191 2. Modeling of High-Pressure Phase Equilibria 191 1982 Publications and Reports 192

III. NUCLEAR SCIENCES A. Low-Energy Nuclear Science 1. Heavy Element Chemistry Actinide Chemistry Norman M. Edelstein, Richard A. Andersen, Neil Bartlett, John G. Conway, Kenneth N. Raymond, Glenn T. Seaborg, Andrew Streitwieser, Jr., David H. Tenipleton, and Alan Zalkin, Investigators Specific Sequestering Agents for the Actinides 1. Lipophilic Enterobactin Analogues. Terminally N-Alkylated Spermine/Spermidine Catecholcarboxamides 195 2. Ferric Ion Sequestering Agents. Selectivity of Sulfonated Poly(Catechoylamides) for Ferric Ion 196 3. Gallium and Indium Imaging Agents 197 4. Synthesis and Structural Chemistry of Tetrakis(Thiohydroxamatcl

Hafnium(IV) in Hf(CH3C6H4(S)N(0)CH3)4-C2H50H '. 197 Synthetic and Structure Studies of Actinides and Other Compounds 1. Organouranium Complexes of Pyrazole and Pyrazolate. Synthesis

and X-Ray Structures of U(C5Me5)2Cl2 (C3H4N5),

U(C5Me5)2Cl(C3H4N2), and U(C6Me5y(C3H3H2)2 198 xvn

2. Synthesis and Crystal Structures of the Tetrafcis(Methy- Trihydroborato) Compounds of Zirconium(IV), Thorium (TV), Uranium(IV) and Neptunium(IV) 198 3. Tertiary Phosphine Complexes of the f-Block Metals; Preparation of Pentamethylcyclopentadienyl-tertiary Phosphine Complexes of Ytterbium (II and III) and Europium (II). The

Crystal Structure of Yb(Me5C5)2Cl(Me2PCH?PMe2) 199 4. Preparation and Crystal Structure of Bis[8is(Pentamethy1- cyc1opentadienyl)Ytterbrium(IIl)]un Decar.arbonylferrate, C(He5C5)2Yb]2[Fe3(CO)n3: A Compound with Four IsocarLonyi (Fe-CO-Yb) Interactions 200 5. Tertiary Phosphine Complexes of the f-Block Metals: Crystal

Structure of Yb[N(SiMe3)2l2 [Me2?CH2CH2PMe2]: Evidence for a Ytterbium-Y-Carbon Interaction 201 6. Stereochemistry of Bis(Carboxylato)Bis (Chloro)Bis(Tertiary Phosphine) Dimolybdenum Complexes; Crystal and Molecular Structure of Two Isomers of (Me3CC02)?Cl2(PEt3)2Mo2 201 7. Anomalous Scattering by Praseodymium, Samarium and Gadolinium and Structures of Ethylenediaminetetra- acetate Salts 202 8. Dipotassiumo Bis-([8]Annulene)Ytterbium(II) and Bis-([83Annulene)-Cal.-ium 203 Physical and Spectroscopic Properties

1. Optical Spectroscopy and Electron Paramagnetic Resonance of Pa4+ in ThBr4 and ThCl/i Crystals 203 2. Fourier Transform Spectrometry Observations of the Actinides 204

1982 Publications and Reports 205

IV. FOSSIL ENERGY

a. ETectrode Surface Chemistry Phillip N. Ross, Jr., Investigator

1. High Coverage States of Oxygen on Pt(OOl) and (111) 209 2. Adsorptive and Catalytic Properties of Zirconium Overlayers on Pt(OOl) 210 3. Adsorptive and Catalytic Properties of Polycrystalline Pt3Ti 210

1962 Publications and Reports 211

b. Studies of Materials Erosion/Wear in Coal Conversion Systems Alan V. Levy, Investigator 1. The High Temperature Erosion of Ductile Alloys 212 2. Methods for Characterization of Erosion by Gas-Entrained Solid Particles 212 3. Effect of Particle Velocity on the Platelet Mechanism of Erosion 213 4. Erosion of Boride Coatings 213 5. Erosion-Corrosion of Steels in a Burner Duct Test Device 214 6. Erosion of Metals in Liquid Slurries 215 7. Corrosion of Metals in Oil Shale Retorts 216

1982 Publications and Reports 216

Chemistry and Morphology of Coal Liquefaction Heinz Heinemann, Investigator, with Alexis T. Bell, James H. Evans, Richard H. Fish, Alan V. Levy, Eugene E. Petersen, Gabor A. Somorjai, Theodore Vermeulen, and K. Peter Vollhardt, Investigators xvm Introduction 217 Task 1: Selective Synthesis of Gasoline Range Components from Synthesis Gas A. T. Bell, Investigator, with R. Oictor and J. Canella 217 Task 2: Electron Microscope Studies J. w. Evans, Investigator, with 0. J. Coates 218 Task 3: Catalyzed Low Temperature Hydrogenation of Coal G. A. Somorjai, Investigator, with A. Cabrera and R, Casanova . . , . . 218 Task 4: Selective Hydrogenation, Hydrogenolysis, and Alkylation of Coal and Coal Related Liquids by Organometallic Systems K. P. C. Vollhardt, Investigator 219 Task 5: Chemistry of Coal Solubilization R. K. Fish and T, Vermeulen, Investigators, with A. D. Thormodsen 221 Task 6: Coal Conversion Catalysts: Deactivation Studies A. V. Levy and E. E. Petersen, Investigators, with M. West and M. C. Smith 221 1982 Publications and Reports 222

d. Materials Characterization in Fossil Fuel Combustion Products Donald H. 8oone and Alan V. Levy, Investigators 1. Erosion of S1C Hard Coating Materials 224 2. Erosion of Ceramic Thermal Barrier Coatings 224 1982 Publications and Reports 225

e. Solution Thermodynamics of Sulfites and Sulfite Oxidation Mechanisms Leo Brewp;- and Robert E. Connick, Investigators 1. The Nechanism of Oxidation Bisulfite Ion by Oxygen 226 ljt,2 Publications and Reports 226 f. Process Chemicals Parameters in Aqueous Sulfur Dioxide Removal by Lime/Limestone Scrubbers C. Beat Meyer and Robert E. Connick, Investigators 1. The Thermal Decomposition of Aqueous Tri- and Tetrathionate 227 2. The Structure of Dithionite Ion 227 1982 Publications and Reports 227

V. ADVMICED ISOTOPE SEPARATION TECHNOLOGY A. Applications and Assessments of Advanced Techniques a. Isotope Separation by Laser Photochemistry C. Bradley Moore, Investigator 1. Determination of Arrhenius Parameters for Unimolecular Reactions of Chloroalkanes by 1R Laser Pyrolysis 229 1982 Publications and Reports 230 XIX

VI. ENERGY STORAGE Electrochemical Energy Storage James W. Evans, Rolf H. Muller, John Newman, Philip N. Ross, and Charles M. Tobias, Investigators a. Surface Morphology of Metals in Electrodeposition Charles W. Tobias, Investigator 1. Limiting Currents and the Effect of Hydrodynamic Flow on the Morpholo9y of Zinc Deposits 231 2. Modeling of Current Distribution with Active-Passive Kinetics 232 b. Metal Couples in Nonaqueous Electrolytes Charles W. Tubias, Investigator 1. Solubility of Potassium Salts in Selected Organic Solvents 233 c. Engineering Analysis of Electrolytic Gas Evolution Charles W. Tou.as, Investigator I. Studies of Bubble Dynamics with the Mosaic Electrode and an Improved Data Acquisition System „ . . 234 1982 Publications and Reports ..... 234

d. Surface Layers on Battery Materials Rolf H. Muller, Investigator 1. Impedance and Ellipsometer Measurements of Surface Layers on Lithium 236 2. Work in Progress 236 1982 Publications and Reports 237

e. Electrode Kinetics and Electrocatalysis Fhilip N. Ross, Jr.! Investigator 1. Low Energy Electron Diffraction (LEED) Characterization of Metal Electrode Surfaces 238 2. Diffusion Controlled Multi-Sweep Cyclic Voltammetry for a Reversible Deposition Reaction Occurring on Rotating Disk and Stationary Electrodes 239 1982 Publications and Reports . , 240

f. Electrical and Electrochemical Behavior of Particulate Electrodes James W. Evans, Investigator 1. Development and Testing of the Mathematical Model for the Hall-Heroult Cell 242 2. Work in Progress 243 1982 Publications and Reports 243

g. Electrochemical Properties of Solid Electrolytes Lutgard C. De Jonghe, Investigator 1. Impurities and Solid Electrolyte Failure 244 2. Grain Boundaries and Solid Electrolyte Degradation 244 1982 Publication- and Reports 245 XX

h. Analysis and Simulation of Electrochemical Systems John Newman, Investigator

1. Work in Progress . . . 246

1932 Publications and Reports 247

MAGNETIC FUSION ENERGY

a. Structural Materials aid Heldments for High Field Superconductin- Magnets John W. Morris, Jr., Investigator 1. The Magneto-Mechanical Cryogenic Research Facility (MMCR) 249 2. Magnetic Field Effects on Mechanical Properties of Stainless Steels 250 3. Austenitic Fe-Mn Cryogenic Steels 250

1982 Publications and Reports , 250

, NUCLEAR WASTE MANAGEMENT

a. Thermodynamic Properties of Chemical Species in Nuclear Waste Norman M. Edelstein, Investigator

1. Voltammetric Studies of the Np02+ Carbonate Systems 251 2. The Solubilities of Crystalline Neodymium and Americium Trihydroxide - 251 3. Hydrolysis and Hydrolytic Precipitation Reactions for Np0?+, Nd3+, and Cm3+ 253

1982 Publications and Reports 254

WORK FOR OTHERS 1. National Aeronautics and Space Administration (NASA) a. Theoretical Studies of Formyl Radical Formation in Selected Combustion Reactions William A. Lester, Jr., Investigator

1. Work in Progress 255

2. Office of Naval Research

a Structure and Performance of AI2O3 Donald H. Boone and Alan V. Levy, Investigators

1. Platinum Modified Alumina Coatings 7.56

b. Electron-Phonon Coupling and the Properties of Thin Films and Inhomogeneous Superconductors Vladimir Z. Kresin, Investigator

1. Systems Containing Thin Films 257 2. Josephson Tunneling and Proximity Effect 257 3. Work in Progress 258 1982 Publications and Reports 258 XXI

3. Electric Power Research Institute (EPRI) a. Phase Equilibria for Fixed Bed Gasification Products, Byproducts, and Water John M. Prausnitz, Investigator 1. Measurement of Phase Equilibria 259 2. Theoretical Methods for Correlation of Phase Equilibria 259 1982 Publications and Reports 260

b. Inhibitive Salts for Reducing High Temperature Oxidation and Spallation David P. Whittle, Investigator

1. Oxidation of Ni-Cr and Co-Cr Alloys Coated with Reactive Element Salts 261 c. Investigate New Fuel Cell Electrolyte and Electrode Concepts Philip N. Ross, Jr., Investigator 1. The Effect of H2PO4- Anion of the Kinetics of Oxygen Reduction on Pt 262 1982 Publicatitns and Reports 263

d. Improved Beta-Alumina Electrolytes for Advanced Storage Batteries Lutgard C. De Jonghe, Investigator

1. Degradation of Sodium Beto"-Alumina: Effect of Microstructure 264

1982 Publications and Reports 265

X. APPENDICES

Appendix A. Materials and Molecular Research Division Personnel

Scientific Staff 267

Support Staff 278

Appendix B. MMRD Committees 279

Appendix C. List of Seminars 281

Appendix D. Index of Investigators 287 xxiii

Gtnml Introduction

Overshadowing all else that happened in MMRD • Robert G. Bergman received a Sherman Fairchild in 1982 were the deaths in mid-career of two very Distinguished Scholarship in residence at the distinguished investigators. David P. Whittle, California Institute of Technology. who was a Staff Senior Scientist with HMRD and Professor in Residence in the Department of Hate- • Michael Cinta (Graduate Student with Leo rials Science and Mineral Engineering of UCB, died Brewer) received a scholarship from the on July 23, 1982, and Bruce H. Hahan, Professor of Achievement Rewards for College Scientists Chemistry at UCB and Faculty Senior Scientist in (ARCS) Foundation. MMRD, died on October 12, 1982. t Iain Finnie received the 1982 Nadai Award from Several other staff changes occurred during the American Society of Mechanical Engineers the year. John S. Winn of the UCB Department of for outstanding and continuing contributions Chemistry and investigator with MMRD left to in advancing the knowledge on erosive wear become Associate Professor of Chemistry at Dartmouth College in Hanover, New Hampshire. and strength of materials, in furthering high Richard A. Andersen an Associate Professor of the temperature design analysis, and in the teach UCB Department of Cnemistry is now an MMRD inves ing of engineering materials technology. tigator doing synthetic actinide and organoactinide chemistry, and Richard J. Saykally an • Andreas M. Glaeser received a Junior Faculty Assistant Professur of that department is now also Fellowship at UCB, and was elected Arco an investigator with the Division doing chemical Junior Faculty Fellow. physics. Professor Iain Finnie, Chairman of the Department of Mechanical Engineering has become • Heinz Heinemann was honored at the "Advances an MMRO investigator in the area of abrasive, in Catalytic Chemistry II" symposium for his erosive and sliding wear of materials. Eugene research and consulting achievements in catal Haller Professor in the UCB Department of Materials ysis and fossil fuel processing. Science and Mineral Engineering and Scientific Program Director of the National Center for Advanced • Harold S. Johnston received a certificate of Materials, at LBL, has become an MMRD investigator Commendation from the Federal Aviation Admin in electronic materials. istration of the Department of Transportation for his help in fostering a better understand ing of the effects of aircraft exhaust emis At the end of I982t there were affiliated with MMRD eight staff senior scientists, 50 Uni sions on the upper atmosphere. versity of California Berkeley faculty investiga tors, 39 staff scientists, 126 postdoctorals and • Eduardo Kamenetzky (Graduate Student with other temporary scientific personnel, 353 graduate Ronald Gronsky), won a Presidential Scholar students, and a support staff of 75 technical, ship to present his paper, "The Accommodation administrative and clerical personnel—for a total of a Change in Grain Boundary Plane in of 651. During the calendar year, 343 journal Molybdenum," at tl:2 national meeting of the articles and LBL reports were published by members Electron Microscopy Society of America. of MMRD. Students associated with MMRD were awarded 55'Ph.D. and 29 M.S. degrees, t Carl Lampert was elected next General Editor of the International Journal, Solar Energy The success of MMRD in basic research and in Materials, published by North-Holland, graduate student training were among the key Amsterdam. factors that persuaded the Department of Energy and the Office of the President that Director • Yuan T. Lee was one of five United States Shirley's proposal for a National Center for scientists to receive the 1981 Ernest 0. Advanced Materials (NCAM) is built on a solid Lawrence Memorial Award for his distinguished foundation. The entire MMRD staff share in the contributions in the field of energy. honor conveyed to LBL by the inclusion of NCAM as a major new initiative in the President's Budget in January 1983 for proposed funding in FY 1984. t C. Bradley Moore was a Visiting Fellow of the Joint institute for Laboratory Astrophysics. Awards, '.cnors, and appointments received by MMRD personnel ir. 1982: • William H. Miller was named Alexander von Htimbolt U.S. Senior Scientist, 1981-1982. • Four investigators, John Clarke, John M. Prausnitz, David A. Shirley, and Gabor A. • Earl L. duetterties was the Centennary Somorjai were elected Fellows of the American Lecturer, Royal Chemical Society, United Association for the Advancement of Science. Kingdom. xx iv

• Joseph A. Pask was elected to full membership • Gareth Thomas and Melimet Sarikaya were awarded in the International Institute for the Science the 1981 Prize for Physical Sciences by the of Sintering. He also received an Alumni Electron Microscopy Society of America. Honor Award for Distinguished Service in Thomas was also elected a member of the Engineering from the College of Engineering, National Academy of Engineering; was elected University of Illinois at Urbar»a-Champaiqn; Chairman of the Board of Governors of Acta and received the 1982 "Teacher of the Year" Metallurgica, inc., and elected Fellow of the Award from the Committee of the Confucius University of Wales, Cardiff. Commemorative Day Ceremony for outstanding achievement in the field of education, and • Charles W. Tobias was the first recipient of for dedicated service rendered to the Chinese the Electrochemistry Society's Henry B. community. Linford Award for Distinguished Teaching.

• Alexander Pines and his student Warren S. • David P. Whittle, Kenneth A. Gaugler, and Warren received the 1982 J. T. Baker/American Haroun N. Hindam received the following awards Chemical Society Nobel Laureate Signature from the 1982 IMS/ASM International Metallo- Award for Graduate Education in Chemistry. graphic Exhibit held in Orlando, Florida: Pines was also named R. W. Vaughan Plenary Judged 1st in Class No. 7, Pretty Microstruc- Lecturer for the 24th Rocky Mountain Confer tures: "Mystery Towers"; judged 2nd in Class ence, and received the Louis A. Strait Award No. 6, Electron Microscopy-Scanning: "Short from the Northern California Society for Circuit Diffusion in AI2O3 Scales"; and Spectroscopy. awarded honorable mention in No. 6, Electron Microscopy-Scanning: "Continuous Internal • John M. Prausnitz was the Union Carbide Alg03 Precipitates." Lecturer at the State University of New York (Buffalo), and van Winkle Lecturer at the MMRD's National Center for Electron Microscopy University of Texas (Austin). (NCEM) is continuing to develop close to schedule. The new Atomic Resolution Microscope (ARM) was a Paul L. Richards received an Alexander von delivered in December 1982 and its assembly has Humbolt Senior Scientist Award. been impressively rapid. Present progress indi cates that acceptance tests for this unique in • Robert 0. Ritchie and Subramanian Suresh were strument will he completed by June 1983. During co-winners for the 1982 DOE/BES Materials its 9 months of operation the 1.5 MeV High Volt Sciences Division Award for Outstanding age Electron Microscope (HVEM) has been used by Scientific Accomplishment in Metallurgy and more than 40 different scientists coming from a Ceramics for work on "Modelling the Role of broad spectrum of disciplines. Usage is divided almost equally between LBL/UCB and outside micros- Microstructure and Environment in Influencing copists, and the ratio of physical to biological Fatigue Crack Propagation in Metals." Ritchie science use is about 5:1. The Steering Committee was also awarded an Alcoa Foundation which monitors the facility operation and assesses Fellowship. proposals to use the instruments has a new member, Professor John Hren, University of Florida, • Henry F. Schaefer, III, was the Lester P. Kuhn Gainesville, and another member with high resolu Memorial Lecturer, Johns Hopkins University. tion expertise will be added soon. Completion of the ARM Support Laboratory has been delayed by • Glenn T. Seaborg was named President of the the stormy winter, but full occupancy is expected International Organization for Chemical in July. NCEM.'MMRD is hosting the 7th Inter Sciences in Development (IOCD). He was national Conference on HVEM, August 17-19, 1983, appointed by U.S. Education Secretary Bell to and a dedication ceremony for the Center is a new National Commission on Excellence in planned for September 1983. Education (NCEE); was elected President of the International Platform Association; was elected honorary member of the Swedish Royal The MMRD Annual Review of the 1982 Programs Society for his contribution to the develop was held on February 28 and March 1, 1983. Dr. ment of humanity; and was named Interim Harold W. Paxton, Vice President for Research, Director of the Lawrence Hall of Science. U.S. Steel Corporation, served as chairman of the Review Committee. Other members were: Dr. • Gabor A. Somorjai was named by the National Richard Bernstein, Senior Vice President, Occi Academy of Sciences as Distinguished Scholar dental Research Corporation; Professor Michel for an Exchange Visit to China. He also Boudart, Department of Chemical Engineering, delivered the Kilpatrick Lecture at Chicago Stanford University; Professor Richard Bradt, Institute of Technology; and was the Dow Department of Materials Sciences, Pennsylvania Lecturer at Michigan St?.te University. State University; Dr. George W. Parshall, E. I.. Du Pont de Nemours and Company; and Dr. James C. • Subramanian Suresh (Postdoctoral with Robert Phillips, Bell Laboratories. 0. Ritchie) was the winner of the Robert Lansing Hardy Gold Medal from AIME for most This year an outside Review Committee joined promising young metallurgist. the Department of Energy, Division of Chemical XXV

Sciences Program Managers on February 23-25, 1983, University; Henry Taube, Department of Chemistry, to review about one-half of our programs in Chemi Stanford University; and John Yates, Department of cal Sciences. These Committee members were: John Chemistry, University of Pittsburg, who served as Pople, Department of Chemistry, Carnegie-Mellon Committee chairman.

Alan W. Searcy Division Head Materials Sciences 1

A. Metallurgy and Ceramics

1. Structure of Material*

a. Structure and Properties of Transformation Inlerfacea* Ror.ild Gronsky, Investigator

Introduction. Transformation interfaces at a L * 41 boundary. Such decomposition products Include homophase boundaries, heterophase bound are observed to remain localized at the boundary aries „ and "free" surfaces at which solid state and their Burgers vectors correspond to those pre reactions are either initiated or propagated. dicted for the DSC lattice at this misorientation. The goal of this research program is to determine the atomic configurations of such interfaces and Grain boundaries of lower E value frequently to establish the relationship between their exhibited faceting as a response to deformation, detailed structure and interfacial properties where the change in grain boundary plane was (mobility, diffusivity, reactivity, conductivity, accompanied by a change in dislocation structure. ductility) since these strongly influence, if not Evidence was also obtained of the emission of completely dominate, the overall performance of dislocations onto adjacent {110} planes with rem materials. nant decomposition products trapped at the bound ary plane. These mechanisms play a critical role Experiments are carried out chiefly by trans in either promoting or inhibiting the continuation mission electron microscopy, including energy of plastic flow across grain boundaries. dispersive x ray and electron energy loss spec troscopies; results are correlated with theoreti Atomic resolution images were also obtained of cal predictions of interfacial structure and high a z - 41 boundary oriented along its [001] tilt spatial resolution image simulations. axis. These micrographs show clearly that the grain boundary accommodates discrete dislocations separated by a nearly perfect (but visibly de 1. GRAIN BOUNDARIES IN BODY-CENTERED CUBIC formed) bcc crystal (Fig. 1.1). The boundary METALS'1" E. A. Kamenetzky, J. M. Pem'sson, and R. Gronsky

The body-centered cubic metals are a technologically important class of materials, encompassing most ferrous alloys as well as refractories. Their properties are also particu lar 7y sensitive to grain boundary structure, and this fundamental research effort is initially aimed at providing direct experimental data on the atomic structure and deformation characteris tics of grain boundaries in bcc systems. The results reported here have been obtained using specimens of molybdenum, prepared under ultrahigh vacuum to avoid grain boundary segregation.

Attention has been paid to the mechanisms by which deformation of bcc structures can be accom modated at the grain boundary as determined by diffraction contrast imaging methods in the TEM. It has been found that a dominant mode of accom modation is the decomposition of matrix slip dis locations into defects of extended core volume within the grain boundary plane. One observation in particular takes the form

fCHT] 3|j[lTTT] +^[19 22 4] Fig. 1.1. Atomic resolution image of a E = 41 boundary in molybdenum. Atom positions in the unit cell projection of perfect bcc structure are *This work was supported by the Director, Office circled in the lower right. At the boundary of Energy Research, Office of Basic Energy plane, the dislocations are located by their Sciences, Materials Sciences Division of the U.S. Burgers circuits. Recorded on a JEOL JEM 200CX Department of Energy under Contract No. with ultrahigh resolution goniometer, 500,OOOX, DE-AC03-76SF00098. 4-sec exposure time. (XBB 827-5910) 2

dislocations are of two types, b\ « a [100], which 3. TRANSFORMATION INTERFACES IN ALUMINUM AU0YS+ are predicted by 0-lattice theory for the symmetrical boundary, and 02 - a/2[lll], which accom J. Howe, G. Tamayo, and R. Gronsky modate the deviation from the symmetrical (910) position and are responsible for the observed An examination of the structural characteris boundary faceting. Detailed analysis of core tics of G.P. zones in an Al-4.2 at.% Ag alloy was atom positions is under way using computer simu carried out by high resolution electron micros lation of atomic structure and imaging. copy to specifically test the proposed models of Ag-rich clusters. The results (see Fig. 3.1) * * * clearly show that: (1) the zones have relatively large planar facets along {111} yielding an octa +A full account of this subprogram is published hedral shape, and (2) there is no ordering within in LBL-14528, LBL-13822, LBL-14029, LBL-14613, the zones. Furthermore, the images show no de and LB1-14702. tectable distortion in lattice spacing through the zones, although in some cases there is evi dence of unit-cell-height interfacial ledges at 2. GRAIN BOUNDARIES AND INTERFACES IN SEMI the zone-matrix interface. CONDUCTORS1' In a separate study, it was found tb»t substi C. S. Hurty, J. H. Rose, T. D. Sands, J. Washburn, tution of aluminum for chromium and nickel in and R. Gronsky iron-base alloys can be made with little or no loss of favorable microstructures and properties The interfaces studied here include grain characteristic of stainless steels. Microchemical boundaries in polycrystal*. ine silicon, the analysis showed that the added Al is effective in crystalline/amorphous interface in ion-implanted forming a passivating oxide, with some occurrence silicon, and transformation interfaces between of DO3 ordered particles in the matrix. The most phases in copper sulfide. effective strengthening mechanism still appears to be the precipitation hardening resulting from Grain boundaries in fine-grained polycrystal- MgC carbides, with Zr and Ce inclusions responsi line Si have been observed to greatly affect ble for enhanced oxidation resistance. carrier mobility at low to moderate dopant levels either because these boundaries can induce defect * * * states in the bandgap which capture majority carriers or because these boundaries may exhibit ^Research re;jlts from the subprogram are fully dopant segregation which results in electrical published in L8L-14164, LB1-15278, and LBL-15434. neutrality. The latter effect was directly ob served in LPCVD Si doped with 0.6 at.SS P and annealed in the 650 to 800'C rangii. Using a 10 nm electron probe at 100 kV, the ciiount of P at various grain boundaries was quantitatively eval uated by TEH/STEM analysis. To a detection limit of 0.2 it.% P, the occurrence of P segregation was found to depend strongly upon boundary struc ture; the energy of segregation varied between 5 and 10 kcal/mole.

In lattice-resolution studies of As-implanted Si, evidence points to the conclusion that the implantation-i nduced, crystal 1i ne-to-amorphous transformation is rarely "homogeneous" in charac ter. Partially damaged crystals exhibit isolated amorphous and crystalline regions which co-exist with sharp interfaces, an interpretation which is supported by computer simulations.

High resolution imaging of the copper sulfide system has revealed detail on the mechanisms of the transformation from the chalcocite (CujS) to djurleite (Cu1.97_1.g4S) phases. Results suggest that the ajurleite structure can be derived from the low chalcocite structure by the clustering of Cu vacancies into CU20S16 groups which simul taneously order into the periodic framework of djurleite. By all indications, the chalcocite- djurleite interface is both abrupt and fully coherent. Fig. 3.1. High resolution electron micrograph of * * * a G.P. zone in an Al-4.2 at.% Ag alloy. All {111} atomic planes are imaged, showing full octahedral ^Detailed reports of this subprogram appear in zone shape. Recorded on a JEOL JEM 200 CX with LBL-14703, LBL-13746, LBL-14165, LBL-14614, ultrahigh resolution goniometer, 300,OO0X, 2.8-sec LBL-15063, LBL-14873, and LB1-14923. exposure time. (XB8 827-6377) 1982 PUBLICATIONS ANO REPORTS 4. J. Washburn, C. S. Murty, 0. Sadana, P. Byrne, R. Gronsky, *• Cheung, and R. Kllaas, Refereed Journals "The Crystal line-to-Amorphous Transformation In Silicon," LBL-14873. 1. R. Gronsky, "Structure of Surfaces and Interfaces," in Proc. 10th Int. Cong. Elec. 5. C. S. Murty, "Crystalline to Amorphous Trans Micros., J. B. LePoole et al. (eds.J, Deutsche formation In Silicon," Ph.D. thesis, LBL-14923. Gesellschaft fur Elektronmikroskopie, Hamburg, Vol. 2, 1982, p. 325; LBL-H528. 6. T. D. Sands, R. Gronsky, and J. Washburn, "High Resolution Study of the Chalcocite (CujS)- 2. J. H. Rose and R. Gronsky, "A Scanning Trans Djurleite (Cui osoS) Transformation in Cuj.vS Thin mission Electron Microscopy Microanalytical Study Films," LM.-15663. of Phosphorus Segregation at Grain Boundaries in Thin-Film Silicon," Appl. Phys. Lett. 41, 993 7. J. Howe, "Relief Etching for SEN and TEH (1982); LBL-14703. Characterization of Sub-Micron Precipitates in Aluminum Alloys," LBL-15278. 3. J. M. Penisson, R. Gronsky, and J. B. Brosse, "High Resolution Study of a 1 » 41 Grain Boundary 8. G. Taauvo, "Hicrostrocture, Transformations in Molybdenum," Scrlpta Met. 16, 1239 (1982); and Properties of Oxidation-Resistant, Iron-Base, LBL-13822. Aluminum-Modified Alloys," M. S. thesis, LBL-15434. 4. T. D. Sands, J.Washburn, and R. Gronsky, "High Resolution Observations of Copper Vacancy Invited Talks Ordering 1n Chalcocite (CujS) and the Trans formation to Djurlelte (Cui Q7_i 94S)," Phys. 1. R. Gronsky, "High Resolution Imaging of Stat. Sol. (a) 72, 551 (1982); LBL-13746. Interfaces In Close-Packed Structures," ASH Workshop on Imaging and Microanalysis with High 5. P. Ling, R. Gronsky, and J. Washburn, Spatial Resolution, Castle Hot Springs, Arizona, "Electron Diffraction Analysis of Microtwin January 5-9, 1982. Structures in Regrown (111) Silicon," in Proc. 40th Ann. Meeting Elec. Micros. Soc. Am.. 6. W. 2. R. Gronsky, "Typical Problems in Imaging and Bailey (ed.), Claitor's, 198Z, p. 460; L8L-14165. Microanalysis with High Spatial Resolution," ASU Winter school, Castle Hot Springs, Arizona, 6. R. Gronsky, "A High Resolution Study of G. P. January 11-15, 1982. Zones in Aluminum-4.2 at.J Silver," in Proc. 40th Ann. Meeting Elec. Micros. Soc. Am.. G. W. "ailey 3. R. Gronsky, "Interfacial Structure and Segre (ed.), CIaitor's, 1382, p. 722; LBL-14164. gation," Department of Metallurgical and Materials Engineering, University of Pittsburgh, Pittsburgh, 7. E. Kamenetzky, "The Accommodation of a Change Pennsylvania, May 13, 1932. in Grain Boundary Plane in Molybdenum," in Proc. 40th Ann. Meeting Elec. Micros. Soc. Am.. G. M. 4. R. Gronsky, "Analytical Electron Microscopy Bailey (ed.), Claitor's, 1982, p. 722; LBL-14029. of Grain Boundary Segregation," Hitachi Workshop, Mountain View, California, May 22, 1982. 5. J. Howe, "High Resolution Electron Microscopy Other Publications and its Application to the Study of Precipitate 1. L. E. Tanner, A. R. Pelton, and R. Gronsky, Plate Growth," Department of Material', Science "The Characterization of Pretransformation Mor and Engineering, Carnegie-Mellon University, phologies; Periodic Strain Modulations," in Pittsburgh, Pennsylvania, August 26, 1982. Proc. ICOMAT-82, J. de Physique, in press. 6. R. Gronsky, "Atanic Structure of Interfaces: Direct Imaging," Department of Materials Science and Engineering Seminar, U. C. Berkeley, LBL Reports September 30, 19B2. 1. E. A. Kamenetzky, "The Mechanisms of Accommo 7. R. Gronsky, "High Resolution Imaging of dation of Deformation at Grain Boundaries in BCC Interfaces," Joint Meeting of Northern California Materials," M. S. thesis, LBL-14613. Society of Electron Microscopy and Microbeam Analysis Society, U. C. Davis, October 7, 1982. 2. J. H. Rose, "A STEM X-Ray Microanalytical Study of Phosphorus Segregation to Grain Bound 8. R. Gronsky, "Microchemical Analysis of aries in Thin-Film Silicon," M. S. thesis, Interfaces In Materials," Students' Night, ASM LBL-14614. Golden Gate Chapter, Berkeley, Novermber 1, 1982. 3. E. A. Kamenetzky and R. Gronsky, "The Mechan 9. R. Gronsky, "Electron Analytical Instruments," isms of Accommodation of Deformation at Grain ASM Golden Gate Chapter Education Seminar, Boundaries in BCC Metals," LBL-14702. Berkeley, November 6, 1982. b. Mlcroctructurt, Proptrttot, ANoy DMign:, Inorganic

Gareth Thomas, Investigator

INTRODUCTION A. Alloy Design: Medium Carbon Steels A. Alloy Design of Steels. Strength, toughness and ductility are undoubtedly the most 1. CHARACTERIZATION Of THE EFFECTS OF LASER important properties specified for structural HEAT-TREATMENT UPON THE MICROSTRUCTURE AND steels, unless the application involves aggressive MECHANICAL PROPERTIES OF Fe/3Cr/2Mn/0.5Mo/0.3C environments. The major difficulty 1n optimizing these properties comes from the fact that strength J. J. Rayment, W. J. Salesky.t and X. M. Meng* is usually inversely related to toughness and ductility; the increase in the former 1s achieved Recently, high powered lasers have been used at the expense of the latter and vice versa. This to locally heat-treat a variety of engineering is true in the majority of cases when relatively- alloys!»2 in an attempt to produce a surface inexpensive alloying and processing are sought that has undergone rapid heating and cooling and, for a practical alloy development. as a result, has refined induced by the rapid heating/cooling cycle. Thus alloy design programs utilize the concept of two-phase steels as a means of optimizing Fig. 1.1 shows the amount of wear as a function these mutually exclusive properties. The under of different laser processing parameters for an lying principle here is to obtain, by heat treat exncriment set up to examine and continuously ment, composites wherein the advantages of one measure the relative rlldlng wear resistance of phase are optimized while the less desirable fea some laser heat-treated specimens. All the laser tures of this phase are simultaneously mitigated heat-treated specimens wear significantly less by the presence of the other constituent phase. than those conventionally heat-treated (1100*C The size, distribution, shape and volume fraction austenitization for 1 hour and oil quenched). of tha second phase critically control the mechan Moreover, specimens that were processed in an ad ical behaviour of the dual phase systems. As a jacent pass geometry at a laser traverse velocity consequence, these structures offer a degree of of 0.35 in./sec showed less than half the wear metallurgical flexibility that is absent in single experienced by the conventionally heat-treated phase structures or in many precipitation material.3 strengthened systems, for attaining optimum sets of mechanical properties.

Examples are given below of martensite/ tpresent Address: Smith Tool, p. 0. Box C-19511, austenite (-2-5%) mixtures designed for optimum Irvine, CA. combinations of high strength toughness and wear ^Present Address: Wuhan Research Institute of properties in medium carbon steels, e.g., for Materials Protection, Wuhan, China. mining, ordnance, and agricultural applications 1. D. S. Gnanamuthu, "Applications of Lasers in and of martensite/ferrite (~80%) structure for Materials Processing," Am. Soc. for Metals (1979). high strength, good formability and improved low 2. F. D. Seaman and D. S. Gnanamuthu, Metals temperature ductility in low carbon steels, for Progress 8, 67 (1975). applications to sheet, line pipe rods and wires, 3. W. J. Salesky, Ph. D. thesis, University of California, Berkeley, Nov. 1982, LBL-15164. B. Magnetic Materials. Research on magnetic materials is concentrated on three main areas: (1) (Mn, Zn) ferrites, (2) rare earth-cobalt magnets, and (3) Mn-Al-C permanent magnets. wcoaiUM - 500 Watts I Summaries of published results are given below. +>commillonatl)r hMt-trMttd tte;i • I.2VMC,wrapping pmti • >.35VMC • i.2Ymc,r-*

*This work was supported by the Director, Office £00 500 GOO of Energy Research, Office of Basic Energy Sffeto Ofstanc* . mMrM Sciences, Materials Sciences Division of the U.S. Fig. 1.1. Amount of wear as a function of sliding Department of Energy under Contract No. distance for conventional and laser heat-treated DE-AC03-76SF00098. Fe/3Cr/2Mn/.5Mo/.3C, (XBL 826-10345) 2. MECHANICAL PROPERTIES AND MICROSTRUCTURE OF LOWER BAINITE IN A 0.3%C-3%Cr-2% Mn STEEL

Hiroyuki Tokushige* and G. Thomas

A metallographic study of isothemally trans formed lower bainite in a 0.3C-3Cr-2Mn steel has been carried out, and the results correlated with mechanical properties* microstructure as well < as higher hardness and an increased wear resist- ..' ance. Unfortunately, too little research has been carried out i.ito the characterization of the effects of laser neat-treatment upon the microstructure and subsequent mechanical properties of the heat-treated material.

In an effort to bridge this gap, a project has been undertaken in which a continuous wave CO2 laser has been used at two power levels, three different pass geometries and at four different traverse velocities, to examine the effects of these parameters on (1) the microstructures of the heat-affected zone {HAZ), the tempered zone adjacent to the HAZ, and the regions in which overlapping of laser passes has occurred, (2) the microstructures of the different regions men tioned in (1), and (3) the sliding wear resist ance. The alloy chosen for examination was Fe/3Cr/2Mn/0.5Mo/0.3C, an alloy developed through the alloy design program, and one that has already been shown to have not only a good strength/ toughness combination, but also good wear resist ance (both sliding and abrasive). Laser heat- treating produces a surface layer -300-450 pm deep, depending on the laser traverse velocity. F1g;\2.1. Transmission electron micrographs of This heat-treated layer has a microhardness of the .ower bainite isothermally transformed at 600-650 VHN, significantly harder than the matrix 360*C. (a) BF after 10 min of isothermal hold hardness of -450 VHN. This increase in hardness ing, (b) OF image of retained austenite in the is the result of a refinement in grain-size (from same condition, (c) BF after I hour of isothermal a matrix value of ~250 pm down to -30 pm), as holding (arrows indicate interlath carbides), well as the high level of residual compressive (d) DF image of carbides in the same condition. stress present in the HAZs. (XBB 8212-10841)

Depending on the isothermal holding time at 360'C, the microstructure changed considerably. After 10-min holding, the microstructure, although predominantly martensitic, was found to contain "'"Ph.D. thesis research in progress. regions of lower bainite. Retained austenite was 1. K. Tokushige, MMRD Annual Report 1981, observed not only at the martensite interlath LBL-13840. boundaries, but also at the boundaries between 2. M. Sarikaya, A. K. Jhingan, and G. Thomas, lower bainitic ferrite laths. These laths con Winchell Symposium, ASM-AIME, Oct. 1981, in press. tained the characteristic unidirectional carbides 3. G. Thomas, Met Trans. 9A, 439-450 (1978). (Figs. 2.1a and b). However, when the microstructure became mostly lower bainitic, i.e., after 1-hour holding, no retained austenite was 3. THE NATURE AND ORIGIN OF SLIDING WEAR DEBRIS observed. Instead, there were interlath carbides FROM STEELS+ decorating bainitic ferrite laths in addition to unidirectional intralath carbides (Figs. 2.1c and W. J. Salesky,* R. M. Fisher,5 R. 0. Ritchie, and d). In this condition both strength and tough G. Thomas ness were considerably lower than those of the as-quenched martensite. The mechanism of wear-particle formation during unlubricated sliding wear of several carbon It appears that retained austenite transformed and alloy steels has been investigated by scanning to elongated carbides during the prolonged iso (SEM) and transmission electron microscopy (TEM). thermal holding. Thus with long-time holding, A detailed study by SEM of individual debris par bainite has a very similar structure to that of ticles has revealed that they are plate-like and martensite tempered in the range between 300 and typically 200 to 400 nm in thickness. The thinner 400"C,2 and its low toughness is essentially a particles are generally iron oxides except for consequence of tempered martensite embrittlement.3 tests conducted at low temperatures or in inert 6

atmospheres when predominantly metallic particles plastic flow of material is observed in Fig. 4.1a result. Using SEM automatic image analysis, the with maximum strain occurring at the foremost mean debris particle width was determined to be 1 region of material flow. A very steep strain to 2 ym. Examination of cross sections from bulk gradient is established, and the extent of defor specimens by TEM revealed a fine dislocation cell mation is decreased rapidly away from the worn structure typical of large strain deformation to surface. The depth of deformation is very shal a depth of 10 to 50 ym, depending on the material low (< 5 um from the surface). Very high true and toad. The subsurface cell dimensions and strain is involved in abrasion and is estimated bending of pearlite colonies indicate that the to be > 5005! at the surface.1*2 shear strain near the surface is at least 5. In many instances, a 200 to 300 nm wide zone of lower Wear particles were collected from wear tests, dislocation density, indicative of recovery, was and a typical result is shown in Fig. 4.1b. Com noted immediately below the surface. Some cracks parison of Figs. 4.1a and b indicated that Ifie formed along dislocation cell walls at the bound crack appears to initiate at the region of high ary of the recovered zone; others were associated est strain and propagate along the dirtition par with decohesion of particle interfaces or subgrain allel to the worn surface. Very fine dislocation triple points. Some oxidation then occurs during cells on the order of 250-A diameter are found at separation of the platelet from the parent materi the surface (Fig. 4.1c), al as a consequence of the highly pyrophoric nature of thin metal flakes. * * *

Ph.D. thesis research in progress. "•Accepted for International Conf. Wear, Reston, 1. J. H. Dantenberg and J. H. Zaat, Wear 23, 9 VA, April 1983. 1973. *W. J. Salesky, "On the Fundamental of Sliding 2. W. 0. Salesky, LBL-15164. Wear in Steel," Ph.D. thesis. University of California, Berkeley, Nov. 1982, . BL-1P164. ^Present Address: U. S. Steel, Research Center, 8. Alloy Design: Low-Carbon Dual Phase Steels Monroeville, PA. 1. DESIGN OF HIGH STRENGTH DUAL-PHASE STEEL WIRE 4. FUNDAMENTALS OF ABRASIVE WEAR A. Nakagawa+ and G. Thomas Chi Kong Kwok+ and G. Thomas Conventional hiph strength wire is produced by Abrasive wear can be taken as a set of micro cold-drawing a high carbon pearlitic steel to scopic inelastic deformation and fracture proces large strains with several intermediate annealing ses involving crack initiation and propagation or patenting heat treatments. Dual-phase steels' near the surface. Extensive plastic deformation show great promise as a starting material for can be accommodated due to the hydrostatic nature cold-drawing into high strength wire because of of loading. their high strain-hardening rates and the ductil ity possible with the second phase, lath marten- Results as shown in Fig. 4.1 provide a compre site. Moreover, dual-phase steels do not need hensive understanding of abrasion. Extrusion-type intermediate patenting treatments and instead can

Fig 4.1. (a) Worn surface of Fe/1.2 Mn/0.6Si/0.1C alloy. Microstructure is a duplex of martensite and ferrite. (b) Wear particles of the same material, (c) Dislocation cell structure at the surface (Ni is electro-deposited on the worn sur face for cross-section preparation. (XBB 820-10906) be drawn in one continuous, multipass cold-drawing operation. This 1s shown in Fig. 1.1, which is a schematic of the drawing procedure for both dual- phase steels and pearlitlc wire. Note that three patenting treatments are required for pearlitic wire (dashed line) to produce tire cord, whereas only an Initial heat treatment is required in the dual-phase steel case (solid line). This results in a reduction in the complexity of the operation as well as production cost and energy consumption.

Results have shown that cold-drawn dual-phase steels can exceed the tensile strength require ment of 270 ksi and torsion test requirement of 58 twists in an 8 in. length for automobile tire bead wire. * * * tph.D. thesis research in progress. Patents applied for.

O.250 QUO

Fig. 1.1. Comparison of the drawing schedule and work hardening for dual-phase steel and patented pearlitic wire. (XBL 8210-6760)

C. Magnetic Materials Fig. 1.1. CBO patterns of (Mn,Zn)Fe204 with electron beams incident along [001] zone axis and 1. EM STUDY OF CaO SEGREGATION AT THE GRAIN 1 electron probe placed at (a) interior of the grain BOUNDARIES IN (Mn^ZnjFegO^ "* and (b) region near grain boundary respectively. The symmetry of the Holz lines in the central disk I-Nan Lin,§ R. K. Mishra, and G. Thomas and the intensity distribution of the surrounding disks have lower symmetry in the region near grain Electron diffraction and microscopy studies boundaries. (XBB 817-7040) supplemented by electron spectroscopic techniques such as Auger electron spectroscopy and energy dispersive x-ray spectroscopy were used to char acterize the nature of grain boundary segregation In low loss Mn,Zn-ferrites, CaO is added to in commercial grade (Mn,Zn)Fe204 samples contain fo«"m a high resistivity layer along grain bound ing small quantities of CaO. Chemical analyses aries so that the electrical resistivity of the by AES and EDAX show an enrichment of Ca near the materials increases significantly. There exist grain boundary region. Convergent beam electron two different views on the formation of this high diffraction experiments show that the crystal resistivity layer, namely, (1) the formation of symmetry of the spinel structure is distorted in an amorphous phase containing CaO at the sinter the vicinity of the grain boundary (Fig. 1.1). ing temperature and (2) grain boundary oxidation In-situ heating experiments in HVEM show the as a result of Ca segregation during cooling of existence of a disordered phase at the sintering the sample from high temperature. A recent study temperature. Lorentz microscopy in TEH shows the of CaO-doped Mn,Zn-ferrites showing an amorphous interaction of magnetic domain walls with grain intergranular phase favors the former model. In boundaries. the present study, further experiments were done to ascertain whether CaO enrichment at the grain boundary region occurs during sintering or during cooling. The distribution of Ca on the fractured surface of (Mn,Zn)Fe204 in as-sintered and annealed samples was studied using Auger electron microscopy. In the as-sintered samples, Ca was detected only at intergranular fractured surfaces and not on the intergranular regions. If these samples were heated at 1300*C and then quenched or cooled slowly, the Ca distribution on the fracture surface did not become homogeneous. If the Ca dissolved into the grains at 1300*C and resegregated upon cooling, Ca must be distributed uniformly on the fracture surface in slowly cooled samples. On the other hand, if the intergranular amorphous phase containing Ca only melted upon heating but still continued to stay in the liquid state, Ca distribution must remain unchanged irrespective of whether the sample is quenched or slowly cooled. Thus it is concluded that Ca seg regation at grain boundaries occurs during liquid phase sintering at high temperature. Although the solubility of CaO in (Mn.ZnjFegOa^ decreases with temperature, the segregation of Ca during cooling is not the dominant process by which grain boundaries are enriched with Ca in (Mn,Zn)Fe204- * * *

+In press, J. Applied Physics, 1983. ^Abstracts of LBL-14E92 and LBL-H797. §I.-Nan Lin, "Microstructure and Magnetic Properties of Mn,Zn Ferrites," Ph.D. thesis, University of California, Berkeley, Dec. 1982, Fig. 2.1. Lattice fringe image and selected area

LBL-15434. diffraction pattern (inset) from a Sm2(Co,Fe,Zr,Cu)i7 alloy showing (a) twin variants of 2:17 phase (chevron pattern), (b) 1:5 type cell boundary phase, and (c) z phase with rhombohedral symmetry. 2. DEVELOPMENT OF THE CELLULAR MICROSTRUCTURE IN (XBB 8111-10172A)

THE SmCo7<4-TYPE MAGNETS+ L. Rabenberg,* R. K. Mishra and G. Thomas * * * Permanent magnets with energy products in "terief version of LBL-13395.

excess cf 33 MGOe and iHc over 13 kOe have become *Ph.D. thesis research in progress. a reality in the Sm(Co, Cu, Fe, Zr)7.4 alloy system. Typically these magnets have a cellular microstructure consisting of Sn^Cojj (2:17) cells 3. ELECTRON MICROSCOPY OF Mn-Al MAGNETS* surrounded by SmCojj (1:5) cell walls. The role of heat treatment in the development of this J. S. Gau, R. K. Mishra, and G. Thomas microstructure and also in the chemical parti tioning of various alloying elements has been Warm extruded Mn-Al-C alloys containing 0.8% established. The kinetics of the growth of the Ni have been shown to have the highest (BH)max 2:17 and 1:5 phases have been examined. values among the Mn-Al magnets. The microstruc ture of these magnets were studied using trans

In our recent work, Sm (Co, Cu, Fe, Zr)7s^ mission electron microscopy and diffraction. It alloys, annealed at 1160 - 1200*C and quenched, is seen that the grain size of Ni containing are shown to consist of a heavily faulted hexag alloys is much finer (0.5-1 ym diameter) than the onal structure that provides ample sites for easy magnets without Ni. The grains contain no anti nucleation of the S111C05 phase. It is argued phase boundaries (APS) although the crystal that the development of the cellular microstruc structure of the grains is the ordered Ll0 struc ture consisting of twinned rhombohedral SmgCojj ture characteristics of the phase. The material cells and hexagonal SmCo5 cell boundaries on is heavily deformed with grains highly twinned or pyramid planes occurs by diffusionless transforma dislocated. Individual grains containing more tion of the hexagonal SmjCoiz phase to the rhom than one variant of the {111} <112> deformation bohedral Sn^Coi; phase and subsequent diffusional twins were seen. It is argued that addition of growth of the SmCos phase. The addition of Zr Ni to the Mn-Al-C alloy helps in the deformation favours the formation of a third phase with rhom process. The small grain size and the large num bohedral symmetry, and all these features are ber of twins are responsible for the absence of shown in the lattice fringe image of Fig. 2.1. the antiphase boundaries. 9

Careful tilting experiments coupled with 7. M. M. Oisko, 0. L. Krivanek, and Peter Rez, convergent beam electron diffraction and high "Orientation-Dependent Extended Fine Structure in resolution imaging experiments failed to show any Electron Energy Loss Spectra," Phys. Rev. B 25, kind of precipitation. Lorentz electron micros (1982). copy showed that the twins act as pinning sites for the magnetic domain walls unlike the APBs LBL Reports that are nucleation sites. These observations are correlated with the deformation process and 1. I-Nan Lin, R. K. Mishra, and G. Thomas, the phase transformation in the alloy. "Electron Microscopy Study of the Structure and Composition of Grain Boundaries in (Mn, Zn)Fe204," * * * Proceedings of Advances in Materials Characteri zation, in press, L8L-14892. Presented at the International Magnetic Society Meeting in Montreal, July 20-23, 1982. Submitted 2. M. J. Salesky, R. M. Fisher, R. 0. Ritchie, to IEEE Trans. Magnetics. and G. Thomas, "Mature and Origin of Sliding Wear *Ph.D. thesis research in progress. Debris From Steels," Proceedings of International Conference on Wear Materials, April 11-14, 19B3, In press, LBL-15059.

+ 4. ANNEALING OF HIGH PERMEABILITY (Mn,Zn)Fe204 3. C. Hayzelden, J. J. Rayment, and B. Cantor, R. K. Mishra and G. Thomas "Rapid Solidification Microstructure in Austenitic Fe-Ni Alloys," Acta Met., in press, LBL-14812. The effect of controi-atmosphere annealing on properties of high permeability MnZn-ferrite'was 4. M. Sarikaya, "Crystallography of Lath Marten- studied. The results show that the electrical site and Stabilization of Retained Austenite," resistivity can be increased dramatically due to Ph.D. thesis, LBL-15111. annealing without adversely affecting initial permeability. A processing scheme is suggested 5. N. J. Kim, A. J. Yang, and G. Thomas, for producing additive-free (Mn.ZrOFegOa of "Microstructure-Properties of Directly Quenched high permeability and high resistivity. Nb Containing Low Carbon Steel," submitted to * * * Met. Trans., LBL-14469. 6. C. K. S. Kwok, "Two Body, Dry Abrasive Wear ^Research in progress. of Fe/Cr/C Experimental Alloys-Relationship Between Microstructure and Mechanical Properties," M.S. thesis, LBL-13393. 191)2 PUBLICATIONS AND REPORTS 7. J. A. Wasynczuk, "The Effect of Microstruc Refereed Journals ture on Fatioue Crack Growth in Duplex Ferrite- Martensite Steels," LBL-151I0. 1. L. Rabenberg, R. K. Mishra, and G. Thomas, "Microstructure of Precipitation-Hardened SmCo 8. W. J. Salesky, "On Fundamentals of Sliding Permanent Magnets," J. Appl. Phys. .53, 2389 Wear in Steel," Ph.D. thesis, LBL-15164. (1982); LBL-13395. 9. A. Pelton, "Interstitial Phase Precipitation 2. H. Mori, H. Fujita, R. Sinclair, and in Iron Base Alloys: A Comparative Study," Ph.D. G. Thomas, "Electron Irradiation Induced Crystal thesi!., LBL-14643. line Amorphous Transitions i' Vi—T1 Alloys," Scripta Met. ^6, 589 (1982). 10. J. H. Rose, "A STEM X-ray Microanalytical Study of Phosphorous Segregation to Grain 3. J. S. Gau, J. V. Koo, A. Nakagawa, and Boundaries in Thin-Film Silicon," M. S. thesis, G. Thomas, "Microstructure and Properties of Dual LBL-14614. Phase Steels Containing Fine Precipitates," Fundamentals of Dual Phase Steels AIME 47 (1982), 11. E. A. Kamentzky, "The Mechanisms of Accommo LBL-12177. dation of Deformation at Grain Boundaries in BCC Materials," LBL-14613. 4. G. Thomas, C. Ahn, and J. Weiss, "Characteri zation of Y-Si-Al-0-N Glass and Crystallization," 12. C. C. Ahn and G. Thomas, "Microstructure and J. Am. Ceram. "oc. 65, 185, (1982); LBL-13942. Grain Boundary Composition of Hot Pressed Silicon Nitride with Yttria and Alumina," J. Am. Ceram. 5. C. Y. Kung and J. J. Rayment, "An Examination Soc, in press, LBL-14627. of the Validity of Existing Formulae for the Cal culation of Ms Temperature," Met. Trans. 13A, 13. J.-M. Lang, "A TEM Characterization of Mo?C 328 (1982); LBL-13191. Precipitates in Molybdenum," M. S. thesis, LBL-14295. 6. M. Sarikaya, B. G. Steinberg, and G. Thomas, "Optimization of Fe/Cr/C Base Structural Steels 14. M. H. Harmer, R. K. Mishra, and G. Thomas, for Improved Strength and Toughness," Met. Trans. "Electron Microscopy of Annealed (Ni,Zn,Co)Fe204," 13A, 2227 (1982); LBL-11421. J. Am. Ceram. Soc, in press, LBL-11223. 15. G. Van Tendeloo, K. T. Faber, and G. Thomas, formations, Pittsburgh, PA, Aug. 1981. in press, "Characterization of Long Pericd Polytypoids in LBL-13098. AIN Ceramics," J. Mat. Sci., in press, LBL-H566. Invited Talks Other Publications 1. J. J. Rayment, "Laser Surface Hardening oi 1. G. Thomas, M. Sarikaya, G. D. N. Smith, and Steels," Society of Manufacturing Engineers S. J. Barnard, "Microstructural Basis of Alloy Seminar on Laser Innc*atijns in Manufacturing Design for High Strength, Tough Structural Technology," Palo Alto, ipril 1982. Steels," Proceedings of Advances in the Physical Metallurgy and Application of Steels 28A, Insti 2. G. Thomas, "Fundamentals of Dual Phase tute of Metals, paper 29, 1982, LBL-1"3DT8. Steels," 11th Annual TMS-AIME Meeting, Dallas, February 22-26, 1982. 2. G. Thomas, Y. Fujiyoshi, and N. Uyeda, "Structure Imping of 21R Polytype in Be-Si-N 3. 6. Thomas, "Electron Microscopy Diffraction Ceramics," Proceedings of the 10th International and Spectroscopy—The Modern Approach to Charac Congress on Electron Microscopy, Hamburg, August terizing Solids," University of California, 17-24, 21, T982: Irvine, Physics Department, January 8, 1982.

3. G. Van Tendeloo and G. Thomas, "High 4. G. Thomas, "Atomic Resolution Microscopy and Resolution Electron Microscopy of Sintered AIN," Spectroscopy," Third Conference on Electron Proceedings of 40th Annual EMSA Meeting, Baton Microscopy, Taipei, Taiwan, Republic of China, Rogue, LA, G. W. Bailey (Ed.), 546, 1982. April 1982.

4. M. Sarikaya and G. Thomas, "Solute Element 5. G. Thomas, "The Role of Microstructural Partitioning and Austenite Stabilization in Analysis in Materials Science and Engineering," Steels," International Conference on Solid-Solid Keynote address at official opening of Engineer Phase Transformations, Pittsburgh, PA, Aug. 198T, ing School, National Sun-Yat-Sen University, published in 1982, LBL-13099. Kaohsiung, Republic of Chivia, April 1982.

5. J. J. Rayment and G. Thomas, "Transmission 6. G. Thomas, "Alloy Design of Structural Electron Microscopy of RSP Fe/Cr/Mn/Mo/C Alloy," Steels," Fourth Industrial Liaison Program Proceedings of MRS Symposium on Rapidly Solidi Meeting, Berkeley, CA, March 3, 1982. fied Materials, Boston, MA, Nov. 1981, LBL-13672, March 1982. 7. G. Thomas, "The Future of High Voltage Electron Microscopy," All-Institute Keynote 6. M. Sarikaya and P. Rez, "The Thickness Speaker at South African Institute of Physics Dependence of Energy Loss Spectra," Proceedings Conference, Stellenbosch, Republic of South of 40th Annual EMSA Meeting, Claitors, Baton Africa, July 13-16, 1982. Rouge, LA, G. W. Bailey (Ed.), 436, 1982, LBL-14191. 8. G. Thomas, "Nitrogen Ceramics," Keynote Speaker, South African Institute of Chemistry 7. M. Sarikaya and G. Thomas, "Lath Martensites Conference, Pretoria, Republic of South Africa, in Low Carbon Steels," Proceedings of Inter- July 19-22, 1982. national Conference on Martensitic Transformation Leuven, Belgium, Aug. 1982, in press, LBL-14506. 9. G. Thomas, "Design of Strong Ductile, Duples Low Alloy Steels," Keynote Paper at I.U.P.A.P. 8. M. Sarikaya and G. Thomas, "Lath Martensites Conference on Recent Developments in Specialty in Carbon Steels—Are Tney Bainitic?" Inter- Steels and Hard Materials, Pretoria, Republic of national Conference on Solid-Solid Phase Trans South Africa, November 1952. c. Solid. State Phete Transformation Htochanisma*

Kenneth H. Westmacott, Investigator

Introduction. New perspectives and concepts (4) The fundamental connection between crystal continue to emerge from fundamental transmission lattice defects and the accommodation of misfit electron microscope studies of the crystallogra ting precipitates in the parent matrix became phy of precipitation processes. The developing apparent. crystallographic theory based on the results identifies and correlates the fundamental defor * * * mation processes that must occur to allow a pro duct phase to form. Unlike other approaches that TBrief version of LBL-14775, LBL-14776, and consider only the final state, this approach LBL-14777. concentrates on understanding the basic mechan 1. G. B. Olson and M. Cohen, Acta. Met. 27, 1907 isms whereby the final state ~s achieved. A (1979). — major goal of this research is to isolate the principal factors govern•'ng the transformations in order to enhance the possibilities for alloy 2. LEDGE STRUCTURE AND PRECIPITATE GROWTH IN design from first principles. Al-Cu t

The articles that follow summarize recent Ulrich Dahmen and Kenneth H. Westmacott results for diverse alloy systems selected to illuminate two important parameters already iden Extension of the precipitate growth model tified, the type of transformation strain and its established for Pt-C to the substitutional Al-4 associated volume change. Four cases have been w/o Cu system (IPS with -4% misfit) has resulted treated in detail: (1} invariant plane strain in a greatly improved understanding of the nucle- (IPS) with large positive volume change, Pt-C; ation and growth of the e1 phase from the super (2) IPS with small negative volume change, e' in saturated solid solution. Al-Cu; (3) invariant line strain (ILS) with no volume change, Cu-Cr and Fe-Cu; and (4) ILS with After recognizing a simple lattice positive volume change, Mo-C. correspondence for the transformation, the basic conservative and non-conservative growth units were identified. By adding these basic building 1. PRECIPITATION IN THE Pt-C SYSTEM* blocks In combinations which minimized both the precipitate shape and volume change, a growth Michael J. Witcomb, Ulrich Dahmen, and Kenneth H. thickness sequence in perfect agreement with that Westmacott observed experimentally was found. Precipitate growth occurs by the expansion of partial dis In the Pt-C alloy system, plate-shaped pre location loops bounding ledges. Different com cipitates form with IPS and an associated volume binations of shear and prismatic loops correspond change of +50%; it therefore proved ideal for to different ledge heights and growth units. studying the role of vacancies in the transforma Another attractive feature of the proposed model tion. A major part of this work has now been is that misfit accommodation on the broad faces completed and reported in a series of three of the precipitate is also naturally incorporated. papers. To summarize the main conclusions: In addition, the experimentally observed struc tural role of excess vacancies in initiating the &" to e' transformation is now understood. (1) The dilute supersaturated fee Pt-C inter stitial solid solution undergoes a precipitation sequence completely analogous to the Al-4Cu sub * * * stitutional system. Moreover, the previously unknown carbide structure which forms, PtgC, is ""Brief version of LBL-14687. isomorphous with ©' AlgCu.

(2) The indispensable role of lattice 3. THE RELATIONSHIP BETWEEN INVARIANT LINE vacancies for initiating the reaction via the STRAIN AND PRECIPITATE NEEDLE GROWTHt co-precipitation process was demonstrated. Ulrich Dahmen, Patrick Ferguson, and Kenneth H. (3) The recently developed concept of Westmacott coherency! was extended to the mechanisms of precipitate growth, systematically incorporating A different type of structural transformation lattice defects. (ILS without volume change) is exemplified in the alloy systems Cu-Cr and Fe-Cu which develop needle-shaped precipitates.

The growth direction of a precipitate needle *This work was supported by the Director, Office was shown earlier! to originate from an invariant of Energy Research, Office of Basic Energy line along its axis. This condition limits co Sciences, Materials Sciences Division of the U.S. herent needle growth to directions that lie on Department of Energy under Contract No. cones with semi-angies defined by the lattice 0E-AC03-76SF00098. parameter ratio of the parent and product phases. 12

Since, during continued growth the needles lose coherency by the nucleation and growth of shear * * * loops, the crystallography of the available shear fBrief version of LBL-13336. systems places a further restriction on the per 1. U. Dahmen and K. H. Westmacott, Proc. Int. missible growth directions. These principles, Conf. on Solid-Solid Phase Transformations, developed in agreement with an fcc/bcc alloy sys Pittsburgh, PA (1981), in press. tem (Cu-Cr),2 are now being tested by observa 2. G. C. Weatherly, P. Humble, and D. Borland, tions of precipitate needles in a bcc/fcc (Fe-Cu) Acta. Met. 27, 1815 (1979). system representing the structural inverse of the fcc/bcc Cu-Cr.

4. Ho2C PRECIPITATE STRUCTURE AND MORPHOLOGY Figure 3.1a shows a typical area of quenched IN MOLYBDENUM1" and aged Fe-2 w/o Cu foils containing semicoherent needles of fee Cu in a bec ferrite matrix. The J.-M. Lang, Ulrich Dahmen, and Kenneth H. random appearance of the needle axis directions Westmacott is deceptive and results from the distribution of 24 variants of a single crystallographic type of Mo-C represents a class of alloy system in needle. which the transformation is characterized by an ILS with +17% volume change. In spite of its In Fig. 3.1b the orientation relationship of a plate-shaped morphology, the M02C carbide phase Cu needle is shown to agree with the predicted cannot grow by a ledge mechanism because the in Kurdjumov-Sachs relationship. The corresponding variant plane strain condition necessary for such growth is not fulfilled. However, the stresses needle lies in the (lll)fCC (110)DCC common close packed planes. that develop during plate growth as a result of the invariant 1ine transformation strain can be These results demonstrate that the relief of relieved by shear loop propagation. In contrast shear stresses, developed during coherent needle to the IPS case, the loops are inclined to the growth, by shear loop nucleation controls the habit plane. Striated structures observed in the growth process. interface of large carbide precipitates in Mo (see Fig. 4.1) can be interpreted successfully on this basis. The more complex precipitate struc ture and morphology reflect greater restrictions on the available deformation processes and the incomplete plastic accommodation of the more general transformation strains. * * *

tBr-:ef version of LBL-14295 and LBL-14970.

Fig. 3.1. Fe-2 w/o Cu alloy quenched from 850'C and aged 18 h at 750eC showing semicoherent fee Fig. 4.1. MogC precipitate on a (301) habit Cu needles; (a) needle distribution with connect plane in Mo, seen in [100] beam direction. The ing dislocations, (b) selected area ^'.-'fraction straight lines in the precipitate/matrix interface from a single precipitate showing Kurdjumov-Sachs lie along the [Il3] invariant line direction. orientation relationship. (XBB 831-224) (XBB 823-2109) 13

5. WORK IN PROGRESS stitial Alloys: II. A New Metastable Carbide Phase in Platinum," LBL-14775. The present emphasis is on the systematic development of the crystallographic theory for 2. U. Dahmen, M. J. Witcomb, and K. H. the case of coherent precipitates to incorporate Westmacott, "A Study of Precipitation in Inter elastic anisotropy and the effect of coherency stitial Alloys: III. Coherent and Semi-Coherent loss on precipitate morphologies. This advance Growth Mechanisms," LBL-14776. is expected to allow prediction of the morphology, orientation relationship, and growth paths of 3. K. H. Westmacott, M. J. Witcomb, and U. precipitates. Dahmen, "A Study of Precipitation in Interstitial Alloys: IV. The Precipitation Sequence in Pt-C," In the experimental program, the established LBL-14777. principles are being tested further and also applied to more complex alloy systems such as 4. U. Dahmen and K. H. Westmacott, "Ledge Struc bcc/hcp, fcc/dc, and bcc/orthorhombic. ture and the Mechanisms of Precipitate Growth in Al-Cu," LBL-14687.

1962 PUBLICATIONS AND REPORTS 5. A. Pelton, "Interstitial Phase Precipitation in Iron-Base Alloys: A Comparative Study," Ph.D. Refereed Journals thesis, LBL-14643.

1. U. Dahmen, "Orientation Relationships in 6. J. M. Lang, "A TEM Characterization of M02C Precipitation Systems," Acta Met. 30, 63 (1982), Precipitates in Molybdenum," M.S. thesis, LBL-12147. LBL-14295.

2. P.Regnier, N. Q. Lam, and K. H. Westmacott, 7. J. M. Lang, U. Oahmen, and K. H. Westmacott, "Defect Clustering Induced by Secondary Collisions "The Origin of MopC Precipitate Morphology in in Pt(C) Alloys During HVEM Irradiation," Scripta Molybdenum," LBL-I4970. Met. 16, 643 (1982). 3. M. J. Witcomb, "A Method of Alignment for Other Publications Convergent Beam Diffraction in TEM Mode for a JEM-100C Electron Microscope," Ultramicroscopy ]_, 1. U. Dahmen and K. H. Westmacott, "A Novel 343 (1982). Method for Analyzing Phase Transformations from Diffraction Patterns," 10th Int. Cong, on Elec. 4. K. H. Westmacott and U. Dahmen, "Loss of Micros., Hamburg, August 1982. Coherency of Precipitates in Al-Si: An HVEM Study," 40th Ann. Proc. Electron Microscopy Soc. 2. J.-Y. Laval, K. H. Westmacott, and M. C. Am., Washington, D.C., 1982, G. W. Bailey (ed.); Amamra, "Characterization and Structure of Intsr- LBL-14180. granular Glassy Phases in Ceramics," submitted to 5th Int. Conf., The Physics of Non-Crystalline 5. J. M. Lang, "Invariant Line and Loss of Solids, Univ. of Montpellier, France, July 5-9, Coherency in Mo(C) System," 40th Ann. Proc. 1982. Electron Microscopy Soc. Am., Washington, D.C., 1982, G. W. Bailey (ed.); LBL-14014. Invited Talks LBL Reports 1. K. H. Westmacott, "Applications of HVEM in 1. M. J. Witcomb, U. Dahmen, and K. H. Materials Science," Exxon Research and Develop Westmacott, "A Study of Precipitation in Inter ment, Linden, NJ, May 21, 1982. 14

d. National Center for Electron Microscopy*

Gareth Thomas, Ronald Gronsky, and Kenneth H. Westmacott, Investigators

Introduction. The National Center for Electron 1. 1.5 MeV HIGH VOLTAGE ELECTRON MICROSCOPE Microscopy (NCEM) aims to provide state-of-the-art facilities for electron-optical characterization K. H. Westmacott of materials and to develop techniques of imaging, interpretation, and microanalysis. The HVEM was accepted on March 19, 1982 when all instrument performance specifications had been The very high cost of modern instruments met or exceeded. Since that time, in spite of a dictates time-sharing centers where facilities, high-voltage instability problem that developed support, and staff are all available. The present and was difficult to diagnose, work on all 40 of NCEM facilities consist of a 650-kV Hitachi (1969) the original research proposals has been carried and a new 1.5-Mev Kratos microscope largely for out (Table 1.1). Modifications to the original in-situ work, a 1-MeV atomic resolution microscope accelerator design which are being made to cor (ARM), which was delivered in January 1983, and rect problems with the long-term voltage stabil commercial support instruments (JEOL 200 CX, ity have, however, impinged on the experimental Siemens 102 and a JEOL 200 CX analytical micro running time. scope). One of the principles of the facility is that while a microscope is normally dedicated to A wide variety of experiments are being a single purpose, certain projects will use many, conducted on the microscope, with users coming if not all, of these microscopes. Hence, consid from universities, industry, and government labor-- erable outlay is needed for equipment and atories (Table 1.1). The present use ratio of staffing. LBL/UCB to other laboratories is almost exactly unity, and the ratio of physical to biological It is anticipated that the facility will be science use is -8:1. fully operational by May 1983. The Seventh International Conference on High Voltage Electron Many experimentalists have taken advantage of Microscopy will be held at Berkeley on August the various tilting, heating, cooling, and envi 16-19, 1983. ronmental control stages to perform dynamic in- situ studies, and these functions nave been The Center is guided by a Steering Committee enhanced by the acquisition of a videocamera/ whose present non-LBL members are: Drs. M. Simnad image intensifier and magnetic tape recorder. (General Atomic Company), w. L. Bell (General Brief summaries of some typical examples of Electric Company), D. G. Howitt (U.C. Davis), research in progress are given in the following J. J. Hren (University of Florida),J. C. H. Spence table. (Arizona State University), and A. Taylor (Argonne National Laboratory).

Table 1.1. HVEM Research Proposals.

Principal Investigator

R. L. Hines Northwestern University Electron Phase Microscopy

R. Gleeser UCB, Biophysics/Donner "... for electron diffraction and EM image work on thin crystals of proteins and nuclei acids."

T. L. Hayes UCB, Biophysics/Donner "... studying the phagocytic process involved in the uptake of coal combustion particulates (fly ash) by pulmonary macrophase cells."

Stanford University, To study the relationship of atomic Materials Science modes of deformation to mechanical properties such as hardness and toughness in tool carbides

R. Sinclair Stanford University, Investigation of SaTi'03-Based Materials Science Dielectrics

R. Sinclair Stanford University, High Resolution Multi-Beam Lattice Materials Science Imaging of Defects in Compound Semiconductors

H. R. Wenk UCB, Geology and Dislocation Properties of Silicate Geophysics/LBL Garnets

R. Gronsky High Resolution imaging at 1,5 MeV

D. G. Howitt UC Davis, Mechanical In-situ studies of the kinetics of Engineering transformations in nuclear waste glassesa

0. G. Howitt UC Davis, Mechanical In-situ environmental studies of the Engineering leaching behavior in nuclear waste glasses3

T. F. Budinger UCB, Electrical Engineering Blood Brain Permeability Studies and Computer Science/Donner

T. F. Budinger UCB, Electrical Engineering Platelet Architecture and Responses to and Computer Science/Donner Physical Insults

T. F. Budinger UCB, Electrical Engineering Leukemic White Blood Cell Architecture and Computer Science/Donner

J. Steeds University of Bristol, Zone axis critical voltages of layer Physics (England) structured materials

L. Eyring Arizona State University, In-situ studies of phase reactions in Chemi stry PrO

K. K. Westmacott The mechanism of carbon precipitation in platinum

K. H. Westmacott Dynamic hot-stage studies of precipitation development in interstitial and substitutional alloys

K. H. Westmacott NCEM/LBL Dynamic studies of changes in interface structure during the overgrowth of oxide films on metal substrates

J. H. Evans UCB, Materials Science and In-situ reduction studies of NiO and and Mineral Engineering/LBL related materials K. H. Westmacott NCEM/LBL

UCB, Materials Science and High temperature deformation of Mineral Engineering/NCEM/LBL ceramics

Environmental Cell of the High Voltage Electron Microscope. (Continued) Table 1.1. (Continued)

Principal Investigator

J. L. Brimhall Battelle Pacific Northwest Bombarding a MosoNiijn, alloy to Laboratories determine if high energy electrons can render the material amorphous

J. L. Brimhall Battelle Pacific Northwest Bombarding H05QN150 alloys made Laboratories amorphous by sputter deposition by high energy electrons at elevated temperatures to determine if the irradiation enhances the crystallization reaction.

W. Stacy Philips Research Laboratories Transistor Pipes0

D. R. Cli-ke Rockwell International Dissolution Mechanisms of Nuclear Science Center Haste Ceramics3

J. R. Porter USC/Materials Science Direct Observation of the Reduction of Pure and Doped Zinc Ferrite by In-Situ High Voltage Electron Mir.roscopya>D

G. J. Thomas and J. C. Hamilton Sandia Laboratories In-situ oxidation studies on stainless steel3

T. Lechtenberg General Atomic Corporation In-situ observation of deformation and crack-nucleation of embrittled I2Cr-lMo steel0

UCB, Biophysics/Donner ...3D reconstruction of extended cellular processes (axons, fibers, etc.) from serial sections of epon-embedded tissue0

H. S. Gill Hewlett-Packard Laboratory High resolution microscopy on Co-X/Cr bifayer thin/thick film composite

J. Walton LLNL/Biomedical Research HVEM of skeletal muscle mitochondria0 (work completed)

G. Thomas UCB, Materials Science and Mineral Engineering Study of the space group of and NCEM/LBL epitaxially grown garnet films K. Krishnan NCEH/LBL

V. Oayaram and Stanford University ...to study WC-Co samples that have R. Sinclair Materials Science been deformed by micro-indentations0

S. L. Shinde and Stanford University, Deformation studies of (W,Ti)C R. Sinclair Materials Science

W. J. Salesky, NCEM/LBL, MMRD Investigation into the micromechanisms J. J. Rayment» of wear and G. Thomas

D. K. Sadana LBL, MMRD TEM investigations of high energy ion implanted Si and GaAs

C. S. Murty and NCEH/LBL Crystalline to Amorphous R. Gronsky Transformation in Silicon

0. R. Cole UCB/Biochemistry Structural studies of metaphase chromosomes J. J. Ravment LBL/MMRD Laser Surface Hardening of Steels A. Pelton Stanford University, Materials Science Amorphitization of TiNi

R. H. Steinberg UCSF, Physiology Cytoskeleton of the pigment epithelium and photo receptors of the vertebrate retina

Environmental Cell of the High Voltage Electron Microscope.

°Non-D0E Support. Crystallization of Amorphous Metals CRITICAL DISPLACEMENTS FOR AM0RPHJTI2ATI0N

J. L. Br1mha!l+ The HVEM is being used to study the effects of A Crystal electron irradiation on the crystallization of 30 i Orientation amorphous materials. The results are compared 1- with earlier work using heavy ion irradiation. A 110 Q 111 Figure 1.1 shows a region of a partially 2» O 531

crystallized amorphous Fe-Cr-Ni-W alloy after 20 irradiation with 1.5 MeV electrons at 530*C for 1/1s 30 minutes. A slightly accelerated crystalliza z tion rate was observed in the irradiated region. 2 1.5 This behavior is in marked contrast to the ion- * A irradiation results, in which a large decrease in crystallization temperature and the development 2 i.o of an Fe-Cr-WX phase was observed. Q. Ul Radiation-Induced Amorphitization °0.5

A. R. Pel ton* 1 1 1 1 1 1 Further studies were •..onducted on electron- 1.0 1.1 1.2 1.3 1.4 1.5 irradiation-induced amorphitization of Ni-Ti ELECTRON ENERGY MeV intermetallic compounds. Several experimental Fig. 1.2. Plot showing the variation of electron parameters were investigated, and it was shown dose with energy for the onset of amorphitization that the crystalline-to-amorphous transition in a Ni-Ti alloy as a function of crystal orien occurs by atomic displacements. For example, it is now apparent that in the austenite phase (B2 tation relative to the electron beam. crystal structure) the process is a function of (XBL 831-7574) electron energy, dose rate, and crystal thickness, but not of crystal orientation. Figure 1.2 shows

the relationship between electron energy and the number of displacements per atom required for the onset of amorphitization for three orientations. It was also determined that the B2 structure does not disorder prior to becoming amorphous. The martensitic phase, however, readily detwins and transforms to austenite when irradiated. These observations agree well with recent results from Ni+ irradiations, although much greaier electron doses (~1022 electrons/cm2) are required than for ion bombardment (~1016 ions/cm2).

Radiation Damage in Silicate Glasses

D. G. Howitt,§ J. F. DeNatale,5 D. K. HcElfresh§

In an interesting application of the environ mental cell of the HVEM, the behavior of glasses • during exposure to both electron irradiation and leaching environments is being studied. Leaching rates and changes in the glass microstrncture can be studied directly as a function of such vari ables as temperature, partial pressure, irradia tion dose rate, and fluence and glass composition. It is found that in certain temperature ranges silicate glasses form oxygen-stabilized voids and undergo amorphous-amorphous and crystalline- amorphous decomposition.

An example of the microstructural features observed after exposing a silicate glass to water vapor and an electron beam in the HVEM environ mental cell is seen in Figure 1.3. The selective Fig. 1.1. Light and dark crystalline regions in an dissolution or leaching of the glass components Fe-Cr-Ni-W amorphous alloy following irradiation is attributed to attack following radiolytic de with 1500 kV electrons at 530°C for 30 minutes. composition of the water vapor by the electron (XBB 831-237) beam. 18

In-Situ Studies of Precipitation in the Fe-N System

P. Ferguson, U. Dahmen, and K. H. Westmacott

HVEM has been shown to be a powerful tool in in-situ precipitation studies in many age- hardening alloys. Studies are being conducted on nitrogen-ferrite, a system in which the intermedi ate precipitate b.c. tetragonal a" - Fe^Ng t'r "ss on {100} matrix planes as discs thin in the c direction. The aH structure consists of eigTft body-centered cubic ferrite unit cells distorted by ordered nitrogen atoms occupying two of the 16 octahedral interstices whose tetrad axes are par allel with one of the cube directions, i.e., the £ edge. At temperatures >250"C, a" transforms rapidly to the equilibrium precipitate Y'-^N, which has an f.c.c. arrangement of metal atoms with a single nitrogen atom occupying an ordered position in the central octahedral interstice. Fe4N often precipitates as HV"-section double platelets and has the orientation relationship with the parent ferrite (112)Y' i| (210)f; [110]f' \\ [001}f. The o"-Fei§N2 structure can be regarded as a distorted y' ""> which alternate nitrogen atoms are missing and which fits with the ferrite matrix with a Baker-Nutting orienta tion relationship (001)f || (OOl^Np. 5;

[110]f || [100]Fe4No.5; it seems therefore that Fig. 1.3. Selective dissolution of the surfaces M of a silicate glass during combined exposure to y'-Fe^N can be nucleated from a by nitrogen water vapor and high energy electrons in the HVEM. enrichment. This hypothesis was tested by heat {XBB 831-238) ing at 285*C an Fe-0.08 wt% N thin foil that ini tially contained stress-oriented a"-FeigN2 pre cipitates. It is clearly seen in Fig. 1.4 that

Fig. 1.4. In-situ aging study, on an Fe-0.08 wt% N alloy in the HVEM operating at 500 kV. the sequence of micrographs show the nucleation and growth of -y'-Fe^N from dissolving a"-precipitate. Beam direction near to [001]. (XBB 831-315) 19

after 4 minutes, a V-shaped y' particle is nucle ated at a shrinking o" precipitate. The T' par ticle, once formed, readily grows with a complex double-HV" morphology as the surrounding o" pre 4 • • cipitates dissolve. The particle marked A is the Zr broad face of a y' platelet growing from an adja * * cent region. This observation of y' nucleation at a" particles has been found in other in-situ experiments and confirms the aforementioned mech * * anism by which Fei5N2 transforms to FeflN. 0

+Battelle-Pacific Northwest Laboratories. ^Stanford University. Sue Davis. .515 nm

2. ATOMIC RESOLUTION MICROSCOPE

R. Gronsky

Final factory certification of the Atomic Resolution Microscope (ARM) was given on November 19, 1982 at JEOL, Ltd., Tokyo, Japan. By then, the microscope had either met or exceeded all factory performance tests, including a convincing demonstration of resolution (Fig. 2.1). This is an impressive result, since the factory is not equipped with a vibration isolation system; in fact, no resolution test was specified for the factory site because of potential problems with mechanical instabilities.

Other performance data include a voltage stability of 8 x 10"' volts per minute and rip ple of 7 x 10-7 volts at top accelerating poten tial (1 MeV). The vacuum in both the specimen stage area of the column and the accelerating tube was in the mid 10~8 torr range. The most critical design feature of the new instrument, its biaxial tilt-lift stage, also yielded out standing results (Fig. 2.2). Fig. 2.1. (a) Structural model and (b) atomic Installation in the ARM building began on resolution image of zirconia Zr02, illustrating January 10, 1983. The microscope should be ready the factory resolution performance of the ARM. for initial tests of its electrical system by [(a) XBL 828-10954; (b) XBB 828-6828] mid-February 1983.

The ARM Support Laboratory (ASL) is also under construction, with a projected completion date in May 1983. This addition to Building 72 will house support microscopes, specimen preparation equip ment, and image analysis hardware. 20

Fig. 2.2. Tilting experiment designed to test the range of the new double-tiIt-lift goniometer stage in the ARM. The entire unit triangle of the Si specimen was accessible with no interruptions. (XBB 828-6831)

3. PERIODIC EXTENSION IN OPTICAL DIFFRACTION ANALYSIS* * * *

R. Gronsky and C. S. Murty ''"Condensed version of LBL-14163.

Although optical diffractograms are usually 4. REAL SPACE IMAGE SIMULATION IN HIGH used in high resolution electron microscopy to RESOLUTION MICROSCOPY'*' determine instrumental performance, they can also be used to advantage in the analysis of fine R. Kilaas and R. Gronsky microstructural detail. In optical microdiffrac- tion, a field-limiting aperture in the optical The Atomic Resolution Microscopy project bench system selectively obtains diffraction urgently needs reliable computer simulation of spectra of specific segments of high resolution atomic resolution images so that they can be cor negatives, for a considerable increase in spatial rectly interpreted. Although most image calcula resolution. Unfortunately, diffraction effects tion programs are based upon dynamical multi-slice from the sampling aperture itself often interfere formulations, a new method has emerged, which with the interpretation of results. promises an even more dramatic reduction in calcu lation time. The present work examines the domain In this work, a method to overcome these dif of validity of this new technique, termed here the ficulties has been developed. It is based upon a Real Space (RSP) method. periodic extension of the small region from which a raicrodiffraction pattern is desired, making the The RSP method treats the interaction of the problem a much simpler deconvolution of the de electron beam with the specimen by using an expan sired pattern and that of the periodic array. sion of the propagator exp (ea) to second order in e. Its usefulness therefore depends upon the With proper care to avoid emulsion grain errors introduced by this truncation, and compu- effects (due to high printing enlargement ratios), tetions were performed using botn RSP and fast this method was successfully applied to the study Fourier transform (FFT) algorithms for the same of small amorphous zones (-50A diameter) in a specimen (copper) and imaging conditions. crystalline Si matrix. Information was obtained on the nature of these amorphous zones during a The RSP method gives results similar to the transformation sequence from their periodically conventional FFT calculation when care is taken reinforced scattering patterns. to include enough reflections. To keep within the 21

domain of validity of the RSP method, it might be * * * necessary to reduce slice thickness as the number of reflections increases as needed to maintain ^j. Materials Science (in press). *0n leave from RUCA, University of Antwerp, Jc9max * *'2' If th1s condition is not satis Groenenborgerlaan, Belgium. fied, the RSP method will begin to diverge because ^Partial financial support form the National of j near-exponential growth of higher order re Science Foundation. flections. Nevertheless, for the same number of reflections, the RSP method offers a significant saving in computer time, which is of major impor 1982 PUBLICATIONS AND REPORTS tance for larger calculations. Refereed Journals * * * 1. R. Gronsky and C. S. Hurty, "Periodic +Condensed version of LBL-15345. Extension in Optical Diffraction Analysis," in Proceedings of the 40th Annual Meeting of the Electron Microscopy Society of America, edited by 5. CHARACTERIZATION OF A1N CERAMICS CONTAINING G. W. Bailey (Claiiors, Baton Rouge, 1982), LONG PERIOD P0LYTYP0IDSf p. 428, LBL-14163.

G. Van Tendeloo*5 and G. Thomas 2. K. H. Westmacott, "Life Beyond 1 MeV," Prakt. Met. 19, 474 (1982). Two A1N-Si02 materials have been investigated by means of very high resolution electron micros 3. G. Van Tendeloo and G. Thomas, "High copy carried out in the JEOL 200 CX instrument. Resolution TEM of Sintered A1N," in Proceedings Three new long period polytypes, close to the 2H of the 40th Annual Meeting of the Electron hexagonal A1N structure, have been identified by Microscopy'Society of America, edited by G. H. high resolution electron microscopy, namely 33R, Bailey (CIaitors. Baton Rouge, 1982), p. 546. (Fig. 5.1), 24H, and 39R. These polytypoids are built on the same stacking principle as those in 4. G. Thomas, V. Fujiyoshi, and N. Uyeda, the previously observed shorter polytypes in the "Structure Imaging of the 21R Polytypoid in A1N system. Be-Si-N Ceramics," in Electron Microscopy 1982. 10th International Congress, Deutsche Gesellschaft fur Elektronik, Vol. 2, 21, 1982.

LBL Reports

1. G. Van Tendeloo, K. T. Faber, and G. Thomas, "Characterization of A1N Ceramics Containing Long Period Polytypoids," J. Mat. Sci., in press, LBL-14566.

2. R. Kilaas and R. Gronsky, "Real Space Image Simulation in High Resolution Electron Micros copy," LBL-15345. Invited Talks

1. K. H. Westmacott, "The Berkeley High Voltage Electron Microscopy Facility," Microbeam Analysis Society of Northern California, Sunol, March 5, 1982.

Fig. 5.1. Example of 2.5 A point-to-point reso 2. K. H. Westmacott, "Argonne National Laboratory lution of the 33R polytypoid. The bright dots HVEM Summer Institute Lecture—Kinetics II, correspond to the carbon sites. (XBB 824-3421) Argonne, IL, July 22, 1982, LBL-14720. 22

e. In-SIUi Investigations of G«f-SoMd Reactions by Electron Microscopy*

James W. Evans and Kenneth H. Westmacott, Investigators

Introduction. There is considerable evidence the environmental cell is only equipped with a in the literature that there is a link between single tilt stage. the defect structure of a solid and the kinetics of the reaction with a liquid or gas. However, Figure 1.1 shows two regions of a NiO single Lhere has been little examination of the nature crystal that have been reduced at approximately of this link, presumably because of the diffi 570 K for 90 minutes in a 50 torr, 5% H2 95% Ar culty of simultaneously reacting the solid and mixture. The white areas are pores formed by characterizing its microstructure. Such simul reduction; gray and black areas are Ni of varying taneous measurements are necessary in view of the thickness; the small amount of remaining nickel propensity fo*1 a microstructure to change between oxide in these samples is not evident in these the time of its characterization and any reaction pictures. Diffraction patterns are inset, and it experiments that are subsequent, rather than is remarkable that, even with the extensive re simultaneous. This difficulty has recently been duction and development of porosity evident in overcome witi the use of an "environmental cell" these figures, epitaxy is retained between the in a high voltage transmission electron micro unreacted NiO and the nickel formed by reduction. scope, which permits observation of the micro- This is evident from the absence of "powder" structure as the solid reacts. rings in the diffraction pattern and the presence of double diffraction spots.

1. THE MICROSTRUCTURE AND REACTIVITY OF METAL Fig. 1.2 shows NiO that was reduced in situ, OXIDES subjected to further ion beam thinning, and examined in the microscope (without further ,3. W. Evans, 0. J. Coates,+ and K. H. Westmacott reduction). It is clear that tne porosity of the Ni produced by reaction extends right up to the Reductions of NiO and iron oxide in an interface between the Ni and NiO. This result environmental cell in a 650 kV Hitachi transmis was to be expected since the pores provide the sion electron microscope have been studied. The route for the ready diffusion of hydrogen to this reduction of NiO by H2 is interesting in that interface and of water vapor away from it. there is much evidence that the reaction is sig nificantly affected by the microstructure. Prior Figure 1.3 shows a wUstite (FeO) sample prior work at Berkeley has indicated that cracks pro to reduction (left) and after exposure to a 50 vide sites for nucleate of the Ni phase formed torr, 10% »2* 9°£ Ar mixture at 784 K for 14 by reaction. Experiments in the environmental minutes (right). Fe nuclei are evident across cell suggest that antiferromagnetic domain bound the surface of the wiistite and particularly at aries also provide nucleation sites. This would the edge of the sample. The powder rings of the be consistent with the macroscopic observations, diffraction pattern correspond to Fe, and it is made by other workers* that there is a change in clear that the iron nuclei are not epitaxial with activation energy for reaction at the Ne"el tem the host oxide, in contrast to the case in nickel perature (-520 K). However, the evidence linking oxide reduction. the antiferromagnetic domain boundaries to Ni nucleation is not certain. A double tilt stage is required to properly image the boundaries, and ^Present address: METTEK, Santa Ana, CA 92705.

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Oivision of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. Fig. 1J. Two regions of a nickel oxide single crystal that have been extensively reduced to nickel. Electron diffraction patterns inset. (XBB 821-714)

Fig. 1.2. Nickel oxide specimen that has been ion Fig. 1.3. Ferrous oxide sample before (left) and beam thinned after partial reduction. Pores in after (right) partial reduction. Diffraction the nickel extend to the nickel-nickel oxide pattern of partly reduced sample inset. interface. (XBB 831-790) (XBB 831-791) 24

1982 PUBLICATIONS AND REPORTS 2. S. D. Lympany and J. W. Evans, "An Improved Mathematical Model for Melt Flow in Induction Refereed Journals Furnaces and Comparison with Experimental Data," Met. Trans., in press, LBL-15170. ^l. I. Masterson and J. W. Evans, "Fluidized Bed Electrowinning of Copper; Experiments Using 150 3. D. J. Coates, A. L. Cabrera, J. W. Evans, H. Amp and 1,000 Amp Cells and Some Mathematical Heinetnann, and G. A. Somorjai, "An Electron Modelling," Met. Trans. 13B, 3 (1982). Microscopy Study of the Low Temperature Catalyzed Steam Gasification of Graphite," J. of Catal., in t2. M. Dubrovsky and J. M. Evans, "An Investiga press, LBL-14463. tion of Fluidized Bed Electroi'inning of Cobalt Using 50 and 1,000 Amp Cells, " Met. Trans. 13B, Invited Talks 293 (1982). 1. II. .1. Coat»'s. K. H. Westmacott, and J. w. §3. M. H. Abbasi and J. w. Evans, "Monte Carlo Evans, "Ttie Effect of Microstructure on the Simulation of Radiant Transport through an Reduction of NicUel Oxide," AIME Annual Meeting, Adiabatic Packed Bed or Porous Solid," AIChE J. Las Vegas, Nevada, February 1982. 28, 853 (1982). 2. M. Dubrovsky. J. W. Evans, and T. Huh, 1U. J. N. Barbier, P. Cremer,_J. W. Evans, and Y. "Fluidized bed Electrowinning of Metals at R. Fautrelle, "Simulation Numerique des Fours Moderate Electrical Energy Consumption Rates," Chauffes par Induction," J. de M€canique, Theo- AIME Annual Meeting, Las Vegas, Nevada, February rique et Appliquee 1, 533 (1982). 1982.

5. D. J. Coates, J. W. Evans, and S. S. Pollack, 3. Y. Nakano, M. Abbasi, and J. W. Evans. "A New "Identification of the Origin of Ti02 Deposits Predictive Technique for the Diffusion of Gases on a Hydrodesulfurisation Catalyst," Fuel 61, in Porous Solid," International Symposium on the 1245 (1982), LBL 13244. Physical Chemistry of Iron and Steelmaking," Conference of Metallurgists, Toronto, Canada, 6. D. J. Coates, J. W. Evans and K. H. August 1982. Westmacott, "Defects in Antiferromagnetic Nickel Oxiie," J. of Materials Sci. V, 3281 (1982). 4. S. D. Lympany, R. Moreau, and .1. H. Evans. "Magnetohydrouynamic Effects in Aluminum Reduc 7. J. A. Little and K. H. Westmacott, "The tion Cells," Proc. Int. Union of Theoretical and Origin of Unusual Dislocation Structures Observed Applied Mechanics Symp., Cambridge, England, in Ion-Thinned Nickel Oxice," Metallography 15, September 1982. 259 (l!>82). — 5. S. D. Lympany, D. Ziegler, and J. W. Evans. "Simulation of Electrolyte Flows and Mass Trans Other K'blications port in Electrometallurgy," AIChE Annual Meeting, Los Angeles, November 1982. 1. J. W. Evans, "Physical Chemistry of High Temperature Technology," AIChE J. 28, 868 (1982), * * * book review. ^Supported by the Office of Surface Mining, L8L Reports Department of the Interior. ^Supported by the National Science Foundation. 1. S. D. Lympany and J. W. Evans, "The SSupported by Intramural funds, university of Hall-HeVoult Cell: Some Design Alternatives California- Examined by a Mathematical Model," Met. Trans., USupported by the Institut de Mecanique, in press, LBL-14386. Grenoble, France- 25

ff. Local Atomic Configurations In SoHd Solutions*

Didier de Fontaine, Investigator

Introduction. This research is aimed at understanding basic atomic mechanism leading to J|/Jo—l0 observed microstructures of certain metallic alloys. In particular, work begun after October 1981 has been focused on two topics: (1) a theoretical study of very regular long-period superstructures observed in some ordered alloys and (2) a theoretical study of the kinetics of phase transformations responsible for the change of shape from a "C-curve" to an "S-curveH in transformation-temperature-time (TTT) diagrams of eutectoid carbon steels upon alloying with ter nary substitutional elements. Both of these theoretical studies will be followed by experi mental investigations aimed at confirming (or infirming) the models and at suggesting new directions for further basic research and pos sible applications.

1. LONG-PERIOD SUPERSTRUCTURES

Joseph Kulik and Didier de Fontaine Fig. 1.1. Phase diagram of the axial-next- nearest-neighbor-Ising model (ANNNI) in the Early attempts at explaining the occurrence of antiferromagnetic case. Dashed and full lines long-period superstructures were based entirely represent phase boundaries calculated to first on energy considerations: for example, much was and second order, respectively, in the low made of the lowering of energy resulting from the temperature expansion. (XBL 8212-6981) creation of new Brillouin Zone boundaries near the Fermi surface.* The experimental fact that long-period superstructures often disappeared at Analysis taken to higher orders show that the low temperatures flatly contradicted the predic <221> phase field will further break up into dis tions of such models, however. tinct phase regions, all of structure-type <2J1>. As an example, a superstructure of the pre 3 Recently, new statistical mechanical theories dicted type was observed experimentally in Ag3Mg. have shown long periods in magnetic structures to The analysis further shows that long-period super be caused by the interplay of atomic interactions structures disappear at low enough temperatures, and configurational entropy effects. In particu in agreement with experimental findings. lar, Fisher and Selke (FS)2 have performed a very detailed low temperature expansion of the free energy of an Ising ferromignet with axial nearest and next-nearest competing fJs > 0, Jg < 1. H. Sato and I. Toth, in Alloying Behavior and 0) interactions (ANNNI Model), in vanishing Effects in Concentrated Solutions, Metal!. Soc. applied field. The present study is aimed at Conf., Vol. 29, Gordon and Breach, NY, 1965, extending the FS results to the antiferromagnetic p. 295-419. case {isomorphic to the ordered alloy case), i.e., 2. M E. Fisher and W. Selke, Phil. Trans. Roy. with Jo, Ji» and J2 all negative. S:-. 302, 1 (1981). 3. RTTortier and D. Gratias, Acta Cryst. A36, Results to second order of the low temperature 190 (1980). expansion are shown in the phase diagram of Fig. 1.1. The multicritical point is found at T - 0 K and K « J2/J1 - 1/2. Phase boundaries between TTT DIAGRAMS ordered structures are indicated; <1> denotes the simple antiferromagnetic (or ordered structure); Osamu Dairikij Etienne Colas, and Didier <2> denotes two identical ordered layers followed de Fontaine by two others in antiphase relation with respect to the first two. Symbols <21> and <221> denote Of fundamental importance in heat treating of ordered structures consisting of double and single industrial alloys, steels in particular, is the layers 1n an obvious extension of the notation. determination of their so-called TTT diagrams. There is little hope of ever driving such kinet ic diagrams directly from first principles, but *This work was supported by the Director, Office it would be of considerable interest to discover of Energy Research, Office of Basic Energy what are the most important physical parameters Sciences, Materials Sciences Division of the that influence the shape of the TTT curves, and U.S. Department-of Energy under Contract No. in what way. The limited objective here proposed DE-AC03-76SF00098. is to discover how a ternary (substitutional) 26

addition will affect the C-cjrve of a simple +2. J. M. Sanchez and D. de Fontaine, "Ising eutectoid carbon steel, in particular, under what Model Phase. Diagram Calculations in the fee circumstances (alloying elemeit, concentration, Lattice with First- and Second-Neighbor Inter ...) a "bay" will develop in ';he C-curve to pro actions," Phys. Rev. B 25, 1759 (1982). duce a characteristic S-shape. *3. A. R. Forouhi, B. Sleaford, V. Perez-Mendez, A very simple mathematical model has been D. de Fontaine, and J. Fodor, "Small-Angle X-ray developed for S-shaped TTT curves. The model is Scattering System with Position-Sensitive Detec based on classical nucleation-and-growth theory tor," IEEE Trans. Nucl. Sci. 29, 275 (1982). applied to two austenite decomposition processes: a high temperature one producing pearlite and a +4. D. Gratias, J. H. Sanchez, and low temperature one prjducing bainite. Complete D. de Fontaine, "Application of Group Theory of partitioning of the ternary element between pre the Calculation of the Configurational Entropy in cipitating phases was assumed for the high temper the Cluster Variation Method," Physica A 113, 315 ature mechanism and zero partitioning was assumed (1982). for the low temperature mechanism. i"5. J. M. Sanchez, D. de Fontaine, and Calculated TTT "start" and "end" curves are W. Teitler, "Comparison of Approximate Methods shown in Fig. 2.1; model parameters were chosen so for the Study of Antiferromagnetism in the fee as to simulate experimentally determined S-curves Lattice," Phys. Rev. B 26, (1982). of a near-eutectoid Fe-C-Cr steel. The present model is still very primitive; it is being modi Other Publications fied so as to allow variable partitioning, to be determined, at each temperature, by optimizing +1. D. de Fontaine, "Studies of the Thermo overall growth kinetics. Also, a more realistic dynamics of Ordering by the Cluster Variation evaluation of parameters is being developed. Method," Proc. International Conference on Solid-Solid Phase Transformation, American Society for Metals, Metals Park, Ohio, 1982.

t*2. D. de Fontaine, "Compositional Instabili ties," in II Nuovo Cimento Course on Mechanical T(K1 and Thermal Behaviour of Metallic Materials, G. Caglioti and A. Ferro Milone, tds., Enrico Fermi School of Physics, 1982.

3. D. de Fontaine, "Le Francais Scientifique," La Recherche 13, 812 (1982), in French. Invited Talks

1. D. de Fontaine, "Kinetic Paths in Metallurgi cal Phase Transformations," Workshop on Kinetics of Phase Changes, Institute for Theoretical Physics, Santa Barbara, California, March 1-5, 1982.

2. D. de Fontaine, "In Phase with Phase Diagrams," Northern California AIME Student Meeting, University of California, Berkeley, California, March 21, 1982.

Log (t) 3. D. de Fontaine, "Coherent Phase Diagrams in the Cluster variation Approximation," Alloy Fig. 2,1. TTT curves calculated according to a Workshop, Los Alamos National Laboratory, New simple nucleation-and-growth model with parameters Mexico, September 9, 1982 and Alloy Phase Diagram chosen so as to resemble S-curves of Fe-C-Cr near- Symposium, Materials Research Society Annual eutectoid steels. (XBL 8212-6982) Meeting, Boston, Massachusetts, November 2, 1982.

4. D. de Fontaine, "First-Principles Phase Diagram Calculations, a Possibility?" ALCOA Research Laboratory, Pittsburgh, Pennsylvania, 1982 PUBLICATIONS AND REPORTS October 13, 1982.

Refereed Journals

+1. J. M. Sanchez, D. Gratias, and •this work was supported in part by ARO(D) under 0. de Fontaine, "Special Point-Ordering in Contract No. P-DAAG29-80-K-0044. General Crystal Structures," Acta Cryst. A 38, *This work was supported in part by NSF under 214 (1982). Contract No. 79-20405a03. 27 2. Mechanical Properties

a. Theoretical Problem* In AHoy Design* John W. Morris, Jr., Investigator

Introduction. The purpose of this research experimental data. Research in progress indi project is to advance the science of alloy de cates that the theoretical results can be ex sign through appropriate fundamental research and tended to other combinations of precipitate and through the systematic development of new mater matrix symmetry. ials that have exceptional engineering properties. The current alloy development projects fall in three areas: new structural steels, particularly those intended for use at cryogenic temperature, 1. J. H. Morris, Jr., A. G. Khatchaturyan, and weld filler metals and welding procedures for Sheree H. Wen, Phase Transformations in Solids, high strength structural steels, and supercon in press, LBL-980O. ducting wire for high field magnets. The sup 2. S. H. Wen, E. Kostlan, M. Hong, A. G. porting fundamental research includes theoreti Khatchaturyan, and J. U. Morris, Jr., Acta Met. cal studies of the microstructure, processing 29, 1247 (1981); LBL-10262. and mechanical properties of materials, and ex 37 H. Hong, 0. E. Hedge, and J. W. Morris, Jr., perimental research in materials characteriza LBL-12973. tion and analysis. 4. Y. C. Shih and J. W. Morris., Jr., Proc. EMSA, 1982, p. 382; V. C. Shih, M.S. thisTsT 161^14284. 1. THE LINEAR ELASTIC THEORY OF PHASE 5. M. Hong, 0. E. Wedge, and J. W. Morris, Jr., TRANSFORMATIONS IN SOLIDS LBL-12973 Rev. J. w. Morris, Jr. and V.-C. Shin 2. DISLOCATION MOTION AT LOW TEMPERATURE+ It has been known since the classic work of Eshelby and Khatchaturyan that the theory of T. Mohri and J. W. Morris, Jr. . linear elasticity can be used to explain many of the most important features of structural phase A number of recent reports suggest peculiar transformations in solids. Recent research has ities in the motion of dislocations at very low shown that the theory yields predictive, quanti temperature. The reports are controversial, but tative results as well. The present research was imply that the unusual behavior is associated undertaken to explore its applicability to pre with changes in the damping force on the dislo cipitation reactions. cation and with interactions between the moving dislocation and applied magnetic fields. There The theory was cast in the most appropriate is little relevant theory to guide the analysis forml and solved in the thin-plate limit to of either effect. obtain general relations for the internal strain and preferred habit of a coherent, tetragonal The free electron gas model was used to es precipitate in a cubic matrix.2 The theory timate the electron damping force on a moving proved widely applicable, but failed in the dislocation in.a normal state. The estimate specific case of the FeigNj precipitate in iron. was checked by computing the contribution of the Further work3 showed that theory and experiment moving dislocation to the electrical resistivity. are in agreement if the finite thickness of the The values obtained show reasonable agreement with nitride is taken into account, and that the the experimental results, and do not suggest anomalies ory then resolves discrepancies *T the reported in the dislocation motion. The calculations were lattice constants of the nitride. extended to estimate the coupling between a mov ing dislocation and an applied magnetic field. The analysis of the nitride habit was con The results indicate that the coupling is tinued during the past year. The habit plane negligible. shift predicted by the theory was observed ex perimentally * Further theoretical computa On the basis of these results we conclude that tions showed that the habit plane shift should be the low temperature anomalies in plastic flow are accompanied by a change in both the constrained either experimental artifacts or are caused by lattice parameters and the apparent symmetry of factors other than the electromagnetic properties the nitride.6 Both predictions agree with the of single dislocations.

3. MICROSTRUCTURAL SOURCES OF THE UUCT1LE-TO- BRITTLE TRANSITION IN STEEL

G. Fior, H. J. Kim, P. Johnson-Walls, and J. W. Morris, Jr.

A typical structural steel undergoes a dra matic loss in toughness when it is cooled below its ductile-to-brittle transition temperature (TB). As the name implies, the transition is marked by a change in the fracture mode, from ductile rupture to brittle fracture by transgranular cleavage or intergranular separation. To design steel microstructures that insure a low

value of TB, it is essential to identify the microstructural mechanisms that lead to the transition. Two classes of theory exist. The first emphasizes changes in the flow properties of the steel and suggests that the transition is caused by changes in the mode of ductile rupture. The second, which has been used in our own prior work, holds that the transition occurs because of the intrusion of the brittle fracture mode.

The two interpretations of the transition can be tested against the geometry of the fracture surface. A change in the mode of ductile rupture should alter the type and shape of the rupture dimples that dot the fracture surface, while the intrusion of brittle fracture should appear as a simple increase in the area fraction of brittle fracture. The fracture surface of quenched 5.5Ni steel was studied as a function of the tempera ture of fracture, using stereo fractography and quantitative stereological techniques to charac terize the fracture features.! some of the central results are plotted in Fig. 3.1. They show a clear intrusion of brittle fracture against a background of ductile rupture that is remarkably constant in its morphology. The demonstration that the ductile-to-brittle transition occurs through of the intrusion of the brittle mode, at least in the class of steels represented by 5.5Ni, supports the alloy design approach previously taken in this group: to lower Tg by decreasing the microstructural dimen sion of cleavage fracture.2 The same approach is applicable to ferritic wsldments in low tempera ture steels, as work completed during the past year has shown.3 Research is currently under way to generalize the stereological results to other alloy systems and to identify more precisely the Fig. 3.1. The Charpy impact energy of 5.5Ni microstructural features that effectively inhibit steel is plotted as a function of temperature cleavage fracture. and compared to three stereological measures of the fracture surface: the aspect ratio, V, of the ductile dimples and cleavage features; the surface roughness; and the area fraction or density of dimples. The figure shows that the 1. G. 0. F1or, M. S. thesis, LBL-1475. geometry of ductile rupture remains constant 2. S. Jin et al.f Met. Trans. 6A, 1569 (1975); while the ductile fraction decreases on passing C. K. Syn et al., Met. Trans. Tf£ 1827 (1976); through T . (XBL 8110-6898A) M. Niikura and J. W. Morris, Jr., Met. Trans 11A, B 1531 (1980), LBL-9798; J. I. Kim and J. W. Morris, Jr., LBL-9956. Materials Conference, Kobe, Japan, edited by 3. H. J. Kim, H. K. Shin, and J. W. Morris, Jr., K. Tachikawa and A. Ctark, Butterworths, London, Proceedings of the International Cryogenic England, 1982, p. 129-133; LBL-14175. 29

4. THE COUPLING BETWEEN MAGNETIC- AND Some years ago a Mossbauer laboratory was DEFORMATION-INDUCED MARTENSITE IN METASTABLE established here and the effect was used to meas AUSTENITIC STEELS ure the fraction of austenite in bulk alloy steels and on fracture surfaces.! Further experimental B. Fultz, G. H. Chang, and J. W. Morris, Jr. development and theoretical work2 made it possible to use Mossbauer spectrometry in an increasingly The martensitic transformation in steels is quantitative way. The technique was then used to promoted by high magnetic fields and by plastic study chemical segregation during the tempering strain in ways that are only partly understood. of ferritic Fe-Ni steel. Both types of loading increase the thermodynamic driving force for the martensitic transformation, Research completed during the past year3 yields at least in isolated regions within the material, new in'ormation on the segregation of alloying and may influence martensite nucleation as well. species to austenite during the intercritical It is not known whether the two effects are addi tempering of 9Ni steel. Ni, Mn, Cr, and Si were tive or reinforcing. Their coupling may have found to gather in the austenite. The addition engineering significance, since the austenitic of ternary solutes to the Fe-9Ni binary altered steels that are most commonly used in the struc both the rate of austenite formation and its tures of high field superconducting magnets are thermal stability. The austenite phase boundary metastable at the 4 K service temperature. was displaced toward lower Ni concentrations by several of the solutes. The solute concentra Two experimental devices were set up to tion in the austenite is strongly influenced by study deformation-induced martensitic trans the diffusivity of the solute relative to Ni. A formations in high magnetic fields. The first corollary research effort advanced the quantita employs a pulsed magnet to apply magnetic pulses tive theory of backscatter Mossbauer spectros of strength up to 16 T to a specimen that is copy.'' prestrained in a bolt loading fixture. The second utilizes a large-bore superconducting * * * magnet to impose steady fields of up to 8.5 T on test specimens in a universal cryogenic 1. B. Fultz, M. S. thesis, LBL-7671. testing machine (the MMCR facility). These 2. B. Fultz and J. W. Morris, Jr., Nucl. devices are being used to investigate the Instrum. Meth. 188, 97 (1981); LBL-11022. martensitic transformation in the metastable 3. B. Fultz, PnT~D. thesis, L8L-13588. austenitic steels 304L and 304LN, and the 4. B. Fultz and J. W. Morris, Jr., in press, transformation of precipitated austenite in LBL-15433. tempered 9Ni steel.

The initial results* show that the strain 6. THE METALLURGY OF Fe-Mn STEELS and the field do reinforce. The degree of transformation is measurably Increased when H. J. Lee and J. W. Morris, Jr. prestrained 304L or 304LN is subjected to re peated 16 T pulses at 77 K. The flow stress, The element Mn resembles Ni in many of its elongation, and ultimate tensile strengths of metallurgical effects on alloy steel. It is, the two steels at 77 K are altered when they however, a less costly alloying element, and are tested in an 8 T field. Further tests and has distinct influences on the properties of detailed metallographic studies are in progress. steel that can be useful in alloy design. The Fe-Mn system is not nearly so well researched * * * as the Fe-Ni and Fe-Cr systems. Many of its most interesting and potentially useful prop 1. J. W. Morris, Jr. and B. Fultz, Proceedings erties remain poorly understood. of the International Cryogenic Materials Con ference. Kobe. Japan, edited by K. Tachlkawa and The inherent intergranular fracture mode in A. Clark, Butterworths, London, England, 1982, p. Fe-(10-12)Mn alloys is particularly interesting. 343, LBL-15518; B. Fultz, G. M. Chang, and J. W. Intergranular fracture apparently intrudes be Morris, Jr., LBL-15324. cause of the difficulty of transgranular cleavage through the blocfcy martensite substructure of these alloys. It was shown some years ago* that 5. MuSSBAUER SPECTROMETRY the intergranular mode disappears after the addi tion of a small amount of boron, causing a spec B. Fultz tacular decrease in TR. The optimum grain boundary composition of boron was, however, unclear, as The Mossbauer effect measures the local mag was the reason for the restoration of the inter netic field at a nucleus and is hence useful for granular fracture mode after tempering. distinguishing the paramagnetic austenite phase of Iron from the ferromagnetic ferrlte or mar Auger spectroscopic studies completed during tensite phase. The Mossbauer spectra also con the past year? show that the optimum grain bound tains chemical Information, since the field at ary concentration of b ron is near 3 at.J! and a nucleus 1s influenced by Its environment. It suggest, surprisingly, that the coimion benefi follows that the Mossbauer effect can be a useful cial surfactants Mg and Zr have a negligible in tool in the characterization and analysis of fluence on intergranular fracture. Tempering at steel. 450"C causes an enrichment of the prior austen- 30

ite grain boundary to 32-38 at.% Mn, depending A promising alternative approach is to use a on the boron concentration. This enrichment is multipass gas tungsten arc (GTA) v.elding process presumably responsible for the embrittlement. as a metallurgical treatment to maintain purity It also causes the eventual precipitation of a and to coricrol the microstructure. Each succes grain boundary austenite hase that alters the sive weld pass serves to temper the material pre fracture behavior. Work is continuing on other viously laid down. The technique can be made to aspects of the metallurgy of Fe-Hn steels. wcrk extremely well* and has been commercialized in Jsjjan, but its metallurgical details are still *.* * not understood in the depth needed to exploit its full potential. 1. S. K. Hwang and J. W. Morris, Jr., Met Trans. 10A,. 545 (1979). Research completed during the past year2 2. H. J. Lee, Ph. D. thesis, LBL-14747. identified the mechanism of toughening in 9Ni s^.eel welded with ferritic filler metal. The 9«i base plate is toughened by a distribution of pre 7. HIGH TEMPERATURE EMBRITTLEMENT OF AN cipitated austenite phase. The multipass GTA- IRON-BASEO SUPERALLOr welded plate is tough in both the weld metal and heat affected zone, but, surpisingly, has little G. Hu+ and J. W. Morris, Jr. or no austenite in either region. Rapid thermal cycles are imposed b.v the successive weld passes. Research for the Electric Power Research A cycle to above 700 C refines the microstructure Institute on new alloys for generator retain by destroying the alignment between marten?ite ing rings resulted in the design of a new laths, hence lowering TB- A subsequent cycle iron-based superalloy that combined exception to 500-600"C getters carbon into fine lath bound al strength, toughness, and hydrogen resist ary carbides that raise the toughness in the duc ance at ambient temperature.1 The alloy is tile mode. The results are being used in research a forged and double- aged superalloy of composi Dn the manufacture of cryogenic components by weld tion Fe-34.5Ni-5Cr-3Ti-3Ta-0.5Al-l.0Mo-0.3V-0.01B. buildup. Given its composition ar.d mechanical properties, the alloy may be useful at elevated temperature. * * * Its high temperature properH&s were explored both to test them and to obtain fundamental data 1. H. J. Kim and J. W. Morris, Jr., LBL-13046. on the behavior of high strength Fe-based super- 2. H. J. Kim, H. K. Shin, and J. W. Morris, Jr., alloys. LBL-14175; H. J. Kim, Ph. D. thesis, LBL-14748.

It was foundothat the alloy retained high strength at 650°C in air, but was brittle if it 9. SUPERALLOY WELDING had been solution annealed prior to aging. The fracture was intergranular due to the combination M. Strum, L. Summers, and J. W. Morris, Jr. of grain boundary oxidation and cellular precip itation of a laves phase. An alternate heat Precipitation hardened alloys such as Fe-based treatment was designed to suppress laves phasp supej-illoys must usually be weK-cd prior to aging, formation. The modified alloi had good ductility however, the microc*ructure of the weld differs at 650°C in vacuum, but remained brittle in air. from that of the base metal and may hence have a Metallographic analysis showed that the alloy is Different aging response, causing a strength mis self-embrittling. Surface oxidation during test match in the aged condition. ing induces intergranular precipitation of the laves phase. This phenomenon has been investigated in the iron-based superalloys A286 and JBK-75, a modi * * * fied form of A286 that is more resistant to weld cracking. After welding, both alloys were aged "''Present address: Department of Metallurgy, Jiao at 700*C to precipitate the Ni3Ti hardening phase. Tong University, Shanghai, China. The aging kinetics and hardness were monitored in 1. K. M. Chang and J. W. Morris, Jr., ASTM STP, both the weld and base plate, and their differ 792, in press. ences were correlated to the chemistry and microstructure of the weld.

8. MICROSTRUCTURE CONTROL DURING WELDING OF The results^- show that precipitation occurs FERRITIC STEELS more rapidly in the weld than in the base plate. However, the base plate reaches and maintains H. J. Kim, H. Shin, and J. W. Morris, Jr. higher hardness for all aging times. The re sults are explained by the segregation of ti The fracture toughness of a welded plate is tanium to the interdendritiv. regions of the often lower than that of the base metal because weld metal. Rapid precipitation occurs be of the impurities introduced during welding and tween the dendrites, but the hardened regions the coarse microstructure of the weld deposit and are dispersed and hence do not establish a high heat affected zone. For this reason ferritic low overall strength. Matching weld and base metal temperature steels are often welded with high- properties could be achieved by interposing a alloy austenitic filler metals, sacrificing solution anneal before aging. The details of strengti. and economy to achieve toughness. these processes are still under investigation. 1. M. J. Strum, M. S. thesis, LBL-14750.

10. THE USE OF HEAT TREATMENT TO IMPROVE THE CRITICAL CURRENT OF BRONZE-PROCESS HULTIFILAMEN- TARY SUPERCONDUCTING WIRE*

I. W. Wu, D. Dietderich, J. Holthuis, W. Hassenzahl,* and J. W. Morris, Jr. The most common route to high field Nb3Sn superconducting wire is the "internal bronze" process. In this method niobium rods are in serted into a Cu-Sn bronze billet and drawn into a fine, multifilamentary wire. The wire is then heat treated to form the A15 supercon ducting phase of the niobium bronze interface. The critical current that can be carried by the wire at given values of the temperature and the applied magnetic field is a sensitive func Fig. 10.1. A transmission electron micrograph tion of the composition and microstructure of the of the interface between the columnar and fine A15 layer. It increases if the A15 phase is made grained sublayers of an Nb3Sn reacted layer. more nearly stoichiometric or if its grain size The process of dislocation accumulation into is made smaller. However, the distribution of boundaries is visible. (XBB 824-4087) composition and grain size in the A15 phase with in a multifilamentary wire is not well known.

The present project was undertaken to charac terize the microstructure of a prototype commer cial Nb3Sn superconducting wire as a function ^Supported in part by the Division of High Z-.^rgy of the time and temperature of the reaction heat Physics, U. S. Department of Energy through the treatment and to determine the relation between Accelerator and Fusion Research Division, LBL. the microstructure and the critical current. A *Accelerator and Fusion Research Division, LBL. commercial, 2869 filament wire was procured, heat 1. M. Hong, I. W. Wu, and J. W. Morris, Jr., treated in the temperature range 650-800*C, and Advances in Cryogenic Materials, Vol. 28, Plenum tested to establish its critical current as a Press, New York, 1982, p. 435; LBL-130TJ. function of applied magnetic field at 4 K. Work 2. I. W. Wu, M. Hong, W. Hassenzahl, and J. W. done during the previous year* showed that the Morris, Jr., Proceedings of the International critical current is largely controlled by the Cryogenic Conference, Kobe, Japan, edited by properties of a central, fine-grained layer in K. Tachikawa and A. Clark, Butter-iorths, London, the A15 phase. The combination of grain size and England, 1982, p. 388; LBL-14177. stoichiometry is best if the reaction is done at intermediate temperature, and can be improved further by properly designed double-aging treat ments, with a concomitant improvement in the 11. THE INFLUENCE OF MAGNESIUM ADDITIONS ON THE PROPERTIES OF MULTIFILAMENTARY Nb Sn SUPERCON critical current. 3 DUCTING WIREt

More recent research has concentrated on the I. W. Wu, D. Dietderich, J. Holthuis, J. Glazer, details of the microstructure and mechanisms that W. Hassenzahl,* and J. W. Morris, Jr. control it.2 The grain size and volume frac tion of the fine-grained sublayer of the A15 Work by Tachikawa and co-workers showed that phase were determined quantitatively as a func the addition of Mg to the bronze matrix prior to tion of the temperature of heat treatment. The the formation of bronze-process Nb^Sn tape causes mechanism of formation of the fine-grained layer a significant increase in the critical supercon was found to involve the polygonization of dis ducting current density at 6.5 T, and that this locations into cell walls (Fig. 10.1). The com increase is associated with an apparent decrease position profile within the layer was found by in the A15 grain size. Research was undertaken STEM analysis. The double aging treatments were here to determine whether a similar improvement shown to yield a higher volume fraction of fine would follow the addition of Mg to multifilamen grained material with a flatter, and more nearly tary Nb3Sn wires and to identify the micr'ostruc- stoichiometric composition profile. Given these tural and mechanistic sources of any beneficial results, it was decided to seek chemical additives effort. that might supplement heat treatment to create an A15 phase that is still more uniformly grain- refined. To accomplish this, multifilamentary wires were drawn in the laboratory. They contained 133 32

filaments of pure Nb embedded in bronze with var 1982 PUBLICATIONS AND REPORTS ious concentrations of Sn and Mg. Their critical current densities were measured as a function of Refereed Journals bronze composition, heat treatment, and trans verse magnetic field at 4.2 K. The reacted A15 1. D. t. Williams and J. W. Morris, Jr., layers were subsequently examined using a variety "Weldability of Grain-Refined Fe-12Ni-0.25Ti of microscopic and microanalytic techniques. Steel for Cryogenic Use," Melding J. Suppl., May, p. 133-138, 1982; LBL-11777. The work is incomplete, but the results ob tained to date^ seem sufficient to justify three 2. J. M. Hong, J. Holthuis, I. W. Wu, and J. W. major conclusions: (1) Magnesium additions to Morris, Jr., "Developmental Studies on Powder the bronze increase the attainable critical cur Processed Nb3Al Superconducting Wire," Advances rent at all fields tested (8-15 T). The increase in Cryogenic Materials, Vol. 28, Plenum Press, is large enough to be of technological interest New York, 1982, p. 435-444; LBL-13013. (Fig. 11.1). (2) The magnesium segregates almost completely to the ftt^Sn layer during the reac 3. M. Hong, I. H. Wu, and J. W. Morris, Jr., "An tion. The Mg resides predominantly within the Investigation on the Critical Current Densities A15 matrix; it is not a strong surfactant in in Bronze-Process Nb^Sn," Advances in Cryogenic Nb3Sn. (3) The most obvious effect of the Mg Materials. Vol. 28, Plenum Press, New York, 1982, addition is to retard grain coarsening during p. 43S-44; LBL-13015. growth of the A15 layer, yielding a uniformly fine-grained product. This effect accounts for 4. J. J. Kim, C. K. Syn, and J. W. Morris, Jr., much, if not most of the improvement in Jc. Pre liminary results also suggest that Mg decreases "Ferritic Weldment of Ferritic Ni Steels for Low the A15 grain size and improves the Sn distribu Temperature Use," Advances jri Cryogenic Materials, tion through the reacted layer. It is not clear Vol. 28, Plenum Press, New York, 1982, p. 878-882; what, if any.effect Mg has on the inherent super LBL-13017. conducting properties of Nb3Sn. 5. Y. C. Shin and J. W. Morris, Jr., "The Habit Plane Shift and the Morphology of a" Precipitate in a-Fe," 40th Ann. Proc. Elect. Micro. Soc. Am., 1981, p. 721P729; LBL34T59. Supported in part by the Division of High Energy LBL Reports Physics, U. S. Department of Energy through the Accelerator and Fusion Research Division, LBL. 1. H. J. Lee and J. W. Morris, Jr., "High Res ^Accelerator and Fusion Research Division, LBL. olution Scanning Auger Microscopic Investiga tion of Intrergranular Fracture in As-Quenched 1. K. Tachikawa et al.t Adv. Cryr. Eng. 26, 375 (1980). ~~ Fe-12Mn," Met. Trans., in press, LBL-11629. 2. I. W. Wu et a!., in press, LBL-15336. 2. T. Mohri, "Calculations of the Electron Damp ing Force on Moving Edge Dislocations," Ph.D. thesis, LBL-12223.

3. K. M. Chang and J. W. Morris, Jr., "Research Toward New Alloys for Generator Retaining Rings," Proc. Micro. Conf., in press, LBL-13467. 4. B. Fultz, "A Mossbauer Spectrometry Study of Fe-Ni-X Steel," Ph.D. thesis, LBL-13588.

5. H. J. Kim, H. K. Shin and J. W. Morris, Jr., "The Influence of Rapid Thermal Cycles in Multi pass Welding of Heat-Affected Zone Properties of Ferritic Cryogenic Steels," Proceedings of the International Cryogenic Materials Conference, Kobe, Japan, May 11-14, 1982, Butterworths, England, p. 129-133, LBL-14175.

6. 1. W. Wu, M. Hong, W. Hassenzahl, and J. W. 650 700 730 750 780 TEMP.fC) Morris, Jr., "The Influence of Heat Treatment on 14 8 4 2 1 TIME(Ooys) the Structure and Properties of Bronze-Process AGING CONDITIONS Multifilamentary Nb3Sn Superconducting Wire," Proceedings of the International Cryogenic Fig. 11.1. Plot of the critical superconducting Conference,' 1982, p. 388-391, LBL-14177. current vs the aging temperature for bronze-proc ess multifilamentary Nb3Sn wires with varied Sn 7. Y. C. Shin, "The Observation of the Habit and Mg content in the bronze. The data were tak Plane Shift and the Habit Plane Shift and the en in a 10 T field at 4 K and show the increase Morphology of a" Nitride (FeifiNj) Precipitate associated with the Mg addition. (XBL 8211-6901) in a-Fe," M. S. thesis, LBL-14284. 33

8. H. J. Lee, "The Study of Intergranular Em- 15. B. Fultz and J. W. Morris, Jr., "The brittlement in Fe-12Mn Alloys," Ph. 0. thesis, Thickness Distortion of 5'Fe Backscatter LBL-14747. Mb'ssbauer Spectra: II. Effects of Secondary Resonant Absorptions," in press, LBL-15433. 9. H. J. Kim, "Development of Ferritic Weldments for Grain Refined Ferritic Steels for 4.2 K Ser 16. J. W. Morris and B. Fultz, "Effects of vice," Ph. 0. thesis, LBL-14748. Magnetic Fields on Martensitic Transformations and Mechanical Properties of Stainless Steels at 10. J. H. Hong, "Powder Metallurgy Processed A15 Low Temperatures," Nucl. Instrum. Meth., in press. ND3AI Superconducting Wires," M. S. thesis, LBL-15518. LBL-14749. Other Publications 11. M. J. Strum, "Effects of Welding of Weloment Mechanical Performance in Two Austenitic Steels," 1. J. I. Kim, C. K. Syn, and J. W. Morris, Jr., M. S. thesis, LBL-14750. "Microstructural Sources of Toughness in OJ.T- Treated 5.5Ni Cryogenic Steel," Met. Trans., 12. G. 0. Fior, "Quantitative Analysis of Frac in press, ONR Technical Ref">rt No. 11. ture Modes in Cryogenic 6Ni Steel by Stereo SEM Technique," H. S. thesis, LBL-14751. 2. 0. I. Kim and J. W. Morris, Jr., "A Mi crostructural Analysis of the QLT Treatment 13. I. W. Wu, D. R. Dietderich, J. T. Holthuis, of Ferritic Fe-Ni Cryogenic Steels," Proceed W. V. Hassenzahl, and J. W. Morris, Jr., "The ings of the International Cryogenic Materials Influence of Magnesium Addition to the Bronze on Conference, Kobe, Japan, May 11-14, 1982, But- the Critical Current of Bronze-Processed Multi- terworths, England, p. 315-355, ONR Technical filamentary Nb3Sn," Proc, IEEE, in press, Report No. 12. LBL-15336.

14. J. W. Morris, Or., "Cryogenic Steels," in Encyclopedia of_ Materials Science and Engineering, in press, LBL-15408. b. Mechanical Properties of Ceramics*

Anthony G. Evans, Investigator

Introduction. The current research activity local compression, as dictated by the dissolution is devoted to studies of both high temperature rate constant, and of atom transport through the deformation and failure, and microstructure amorphous phase, as determined by the solubility development during sintering. High temperature of the solid phase and the thickness of the deformation and failure addresses the response of liquid layer, are of central importance to the refractory materials to stress. Research in this failure of these materials. Further studies of area is devoted to the generation of a self- these phenomena, including the influence of the consistent scientific comprehension of the mecha second phase volume concentration and disposition nisms of deformation and failure, using both and of its viscosity/diffusivity, are in progress. experimental and theoretical techniques. The ultimate objective of this study is the develop ment of a scheme for predicting high temperature mechanical failure. +Brief version of LBL-14266.

The development of microstructure during sintering has a direct influence upon the defect 2. A DAMAGE MODEL OF CREEP CRACK GROWTH IN structure in the material and hence, upon the POLYCRYSTALS1* mechanical strength. Much of the microstructure evolution occurs during the final stage of sin M. D. Thouless, C. H. Hsueh, W. Blumenthal, and tering. Research in this area is devoted pri A. G. Evans marily to a study of microstructural changes occurring during this stage, using a combination The slow growth of cracks, formed by damage of theory and experiment. Particular emphasis is coalescence, constitutes an important component devoted both to the pore/grain boundary separa of the net failure time at elevated temperatures. tion phenomenon and to the concomitant coarsening The growth occurs by the nucleation and growth of and pore shrinkage processes. cavities in a damage zone ahead of the crack (Fig. 2.1). The damage ahead of the crack modi fies the crack tip stress field and thus exerts High Temperature Failure an important influence on the crack growth rate. A crack growth model that incorporates the stress 1. HIGH TEMPERATURE FAILURE INITIATION IN LIQUID modifying influence on the damage has been devel PHASE SINTERED MATERIALS'*" oped. The model allows crack advance when the cavities on the grain facet ahead of the crack J. E. Marion, M. D. Drory, A. G. Evans, and D. R. attain a critical size. Grain boundary sliding Clarke

The nucleation and growth of damage in liquid phase sintered ceramics under stress at high tem peratures has been examined both theoretically and experimentally. Damage, consisting of holes and cavities, has been observed by transmission electron microscopy. The damage has been cor related using theoretical analysis. The process of hole nucleation has been analyzed by consider Cretp/domoge field ing viscous flow in the amorphous phase channels. Hole growth has been analyzed by considering the coupled influence of viscous flow and solution/ reprecipitation. Viscous flow permits the exis tence of a pressure gradient in the amorphous phase, which then establishes the chemical poten tial gradient required for the solution/ reprecipitation mechanism of atom transport. Consequently, the atoms of the solid phase can be Viiceut Matrix transmitted through the liquid and allow the JJi ill JN cavities to enlarge. It is demonstrated that solution/reprecipitation is the rate controlling damage mechanism, at most stress levels of inter est. Hence, the processes of solution under ^ 1T*J Viscout Motrin

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Fig. 2.1. A schematic indicating the existence Sciences, Materials Sciences Division of the U.S. of a damage zone ahead of a crack and of the Department of Energy under Contract No. stress field modification induced by the damage. DE-AC03-76SF00098. (XBL 831-5067) within the damage zone is also permitted. Numer ical solutions for the crack growth rate indicate that the crack velocity in ceramics depends on the stress intensity factor, the grain size, the number of grain facets in the damage zone, the characteristic cavity spacing, and the creep rate of the material. Specifically, the creek growth rate increases with decrease in grain size and cavity spacing and increases with increase in the damage zone size and creep rate. Comparisons of the model with experimental results for polycrystalline AI2O3 reveal good consistency. The primary influential variable that presently defies fundamental understanding is the cavity spacing. This spacing has no obvious microstructural asso ciation and evidently requires further study. However, it is important to appreciate the strong dependence of the crack growth rate on the creep rate of the material, by virtue of its effect on the stress amplitude at the crack tip. Hence, creep resistant materials should also be resis tant to high temperature crack growth.

TBrief version of LBL-3.5348.

3. HIGH CRACK GROWTH IN POLYCRYSTALLINE ALUMINA1"

W. Blumenthal and A. G. Evans

The behavior of cracks under stress at high temperature has been studied in a fine grained, polycrystalline A^Oj. Small, brittle cracks in Fig. 3.1. Scanning electron micrographs of troduced by indentation subject to stress inten cracks exposed to creep strains, (a) the crack blunting that occurs at low crack driving force sities, K, less than the critical vlue Kc have been shown to exhibit two types of response. At and (b) the cavitation damage formed on grain facets in the damage zone. (XBB 831-174) K > 0.5 Kc, the cracks blunt without significant growth (Fig. 3.1a) and are thus innocuous with regard -0 mechanical reliability. The blunting involves the creation of damage within shear lobes 4. THE INFLUENCE OF INHOMOGENEITIES ON HIGH at the sides of thj crack and damage coalescence TEMPERATURE FAILURE IN CERAMICS"*" from this region with the crack surface. At higher crack driving forces, crack growth occurs 5. M. Johnson and A. G. Evans by the nucleation and growth of damage in £ small zone ahead of the crack. The damage consists The stress dependence of the failure time has primarily of cavities on two grain interfaces been measured at high temperatures (1400*C) in a (Fig. 3.1b) that coalesce with the crack tip, fine-grained alumina. The failure time, tf, causing incremental crack advance. These obser varied with stress, o, as tf «= o-5. Observations vations provide the basis for a model of crack of the material in interrupted tests revealed the growth above the threshold (Thouless, Hsueh, nucleation of cracks at microstructural hetero Blumenthal, and Evans). geneities during the early stages of the failure process. The failure thus appears to be dominated The behavior of small cracks formed by inhomo- by the crack propagation time. The crack initi geneous damage coalescence (Fig. 3.1a) has also ating heterogeneities are characterized by mater been investigated. These cracks appear to move ial regions that exhibit rapid grain boundary at appreciably lower crack driving forces than grooving ai the test temperature. This behavior the deliberately introduced cracks, even though suggests tht presence of local impurity concen the crac; morphology appears to be similar. The trations that oroduce premature crack nucleation. motion of these small cracks will require further Observations ot *-he fracture surfaces indicate study because they appear to exert a major influ the existence of cavities on two grain interfaces. ence on the failure time (Johnson and Evans). Measurements of the spacing between these cavities suggest, that the spacing decreases as the stress increases. This observation is consistent with the notion that cavities nucleate during grain boundary sliding transients. Analysis of crack Brief version of LBL-15452. 36

growth rates based on crack growth data (Blumenthal and Evans) confirmed that the failure times were crack propagation controlled. *0'- '/""

Brief version of LBL-15451.

Sintering

1. MICROSTRUCTURE EVOLUTION OURING SINTERING: THE ROLE OF EVAPORATION/CONDENSATION* 0.03

C. H. Hsueh and A. G. Evans \ *~*@

The movement of pores with grain boundaries during final stage sintering can occur either by surface diffusion or by evaporation/condensation, A comparison of pore motion by these two mecha 0 0.2 0.4 0.6 OB 1.0 I.Z 1.4 nisms revealed that the evaporation/condensation pDbS ./kf G(^]/P ,fiSoz mechanism dominates at pore sizes in excess of a b 0 critical value determined primarily by the ratio Fig. 1.1. Sintering trajectories predicted for of the surface diffusion parameter to the equi conditions of pore motion by evaporation/ librium vapor pressure. condensation and pore shrinkage by grain boundary diffusion. (XBL 823-5469) At pore sizes in excess of this critical value, the important final stage sintering phenomena of pore breakaway and pore drag have been analyzed. The pore breakaway process has been shown to 2. AN EXPERIMENTAL ASSESSMENT OF PORE BREAKAWAY occur, independently of the pore size, when the DURING SINTERING1" ratio of the grtin Boundary mobility to the equi librium vapor pressure exceeds a relatively low M. Sakarcan, C. H. Hsueh, and A. G. Evans critical value. Hence, pore breakaway, when evaporation/condensation controlled pore motion Intergranular and grain boundary pores have prevails, and the consequent inhibition of com been observed in MgO during the final stages of plete densification can only be averted by impos sintering. Measurement of the shapes of pores ing very stringent conditions on the final stage attached to grain boundaries, subject to distor sintering schedule. Microstructure control is tion (Fig. 2.1), have been used to estimate the thus contingent upon the avoidance of the ratio of the grain boundary mobility to surface evaporation/condensation mechanism, by starting diffusivity for the material using a theory with sufficiently fine powders that the resulting developed during the preceding year. This esti pores are small enough to allow their motion to mate has then been used to predict the critical be surface diffusion controlled. Control of pore size for the separation of pores from two grain growth, e.g., by solute drag, is also grain interfaces, again using a theoretical needed to restrict the formation of large pores analysis completed during the preceding year. that then move by evaporation/condensation. This prediction has been compared with the median size of the intergranular, separated pores Finally, pore drag and the associated grain (Fig. 2.1) measured in the material in the final size, pore size trajectories, have been analyzed stage. The prediction (0.3 urn) is within less (Fig. 1.1). This study indicates that fully than a factor of two (0.3 to 0.6 vm) of the dense materials are only attainable when the median pore sizes determined experimentally. It ratio of the grain boundary diffusion parameter is thus concluded that the presently developed to the product of the equilibrium vapor pressure theoretical description of pore, grain boundary and the square of the grain size exceeds a mini separation provides an adequate basis for the mum value. Again, therefore, fine powders are understanding of the role of separation on micro- critical. structure development during final stage sinter ing. The dominant role of the grain boundary mobility to the surface diffusivity ratio in the separation process highlights the need to obtain a fundamental understanding of the associated +Brief version of LBL-14110. 37

-i—r

RELATIVE LATTICE DIFFUSION / COARSENING •> / 7

PREDICTED SEPARATION CONDITION FOR 'AVERAGE'BOUNDARIES /3)

1 PREDICTED {CRITICAL PORESIZE

O.I 0.3 0.5 I INTRAGRANULAR PORE RAOIUS l/im)

Fig. 2.1. Comparison of predicted and measured critical pore sizes for t.ii? separation of pores from grain boundaries. Also sliown is a distorted pore/grain boundary used to evaluate the kinetic parameter. (XBB 831-236) atom transport mechanisms and their dependence on shown to permit the judicious choice of approxi additives and impurities. Techniques for measur mations suitable for the analysis of the more ing these parameters, in situ, on the appropriate complex sintering problems pertinent to actual microstructural scale, are of paramount powder compacts, such as the sintering of multi importance. ple arrays of ellipsoidal particles.

+Brief version of LBL-14334. TBrief version of LBL-15450.

3. INITIAL STAGE SINTERING WITH COUPLED GRAIN 1982 PUBLICATIONS AND REPORTS BOUNDARY AND SURFACE DIFFUSION1' Refereed Journals C. H. Hsueh and A. G. Evans 1. C. H. Hsueh, A. G. Evans, and M. Spears, Initial stage sintering of fine powders occurs "Microstructure Developmnt During Final Stage by coupled grain boundary and surface diffusion, Sintering: I. Pore/Grain Boundary Separation," in series. Vet, the series process has never Acta Met. 30, 1269 (1982); LBL-12619 1/2. been analyzed. The rates of shrinkage and neck growth that obtain for various ratios of the 2. M. Spears and A. G. Evans, "Microstructure boundary to the surface diffusivity have thus Development During Final Stage Sintering: II. been calculated, numerically, for the sintering Grain and Pore Coarsening," Acta Met. 30, 1281 of rows of spheres, using a finite difference (1982); LBL-12619 2/2. ~ scheme. The scheme allows for a flux of atoms out of the grain boundary and a flux along the 3. A. G. Evans, "The Structural Reliabilty of surface, dictated by the ratio of the surface to Ceramics: A Processing Dependent Phenomenon," J. boundary diffusi.'ity and the surface curvatures. Am. Ceram. Soc. j>5(3), 127 (1982); LBL-12208. A continuous transition from surface diffusion dominance to grain boundary diffusion control is 4. C. H. Hsueh and A. G. Evans, "Microstructure predicted, with the surface adjusting rapidly to Evolution During Sintering: The Role of accommodate the grain boundary flux, even when Evaporation/Condensation," Acta Met. 31, 189 the surface diffusivity is small. The results (1982). — obtained for both large and small values of the diffusivity ratio have been compared with analyt ic approximations for the separate mass transport Other Publications processes. Certain of these approximations have been found to agree relatively well with the 1. A. G. Evans, "The High Temperature Failure numerical solution. This agreement has been of Ceramics," in Recent Advances in Creep and Fracture of Engineering Materials and Structures, 38

edited by B. Wilshire and D. Owen, Pineridge, 3. A. G. Evans, "High Temperature Failure in 1982, p. 53; LBL-13839. Ceramics," Gordon Conference, Plymouth, New Hampshire August 1982. LBL Reports 4. A. G. Evans, "Reliability of Brittle 1. M. Sakarcan, C. H. Nsueh, and A. G. Evans, Materials," Shell Laboratory, Houston, Texas, "An Experimental Assessment of Pore Breakaway October 1982. During Sintering," 0. Am. Ceram. Soc, in press, '3L 14334. 5. A. G. Evans, "High Temperature Failure Mechanisms, Massachusetts Institute of Tech 2. S. Johnson, "The Role of Micrstructural nology, Cambridge, Massachusetts, November 1982. Inhomogeneities on High Temperature Failure," Ph.D. thesis, LBL-14588. 6. C. H. Hsueh and A. G. Evans, "Neck Growth Ouring Sintering," Pacific Coast Regional ?. M. D. Thouless, "Propagation of Creep Cracks Meeting, American Ceramic Society, Seattle, b Cavitation in Fine Grained Materials," M.S. Washington, October 1982. thesis, LBL-14915. 7. J. E. Marion and A. G. Evans, "High Tempera 4. M. Sakarcan, "Experimental Observations of ture Failure Initiation in Ceramics Containing an Pore Breakaway from Two Grain Junctions," M.S. Intergranular Phase," Pacific Coast Regional thesis, LBL-13686. Meeting, American Ceramic Society, Seattle, Washington, October 1982. 5. J. E. Marion, A. G. Evans, M. D. Drory, and D. R. Clarke, "High Temperature Failure Initia 8. M. Blumenthal and A. G. Evans, "The Growth tion in Liquid Phase Sintered Materials," of Cracks Uuring Creep in Alumina," Pacific Coast LBL-14266. Regional Meeting, American Ceramic Society, Seattle, Washington, October 1982. 6. M. D. Huang and A. G. Evans, "The Strain Energy of Twinned Martensite: Applications to 9. M. Drory and A. G. Evans, "A 3-Dimensional

7r02>" LBL-15087. Ellipsoidal Pore Growth Model," Pacific Coast Regional Meeting, American Ceramic Society, Invited Talks Seattle, Washington, October 1982.

1. A. G. Evans and W. Blumenthal, "High Temper- 10. C. Ostertaq and A. G. Evans," Dominant ature Crack Nucleation and Propagation," American Diffusion Processes by Initial Stage Sintering of Ceramic Society, Cincinnati, Ohio, May 1982. AI2O3," Pacific Coast Regional Meeting, American Ceramic Society, Seattle, Washington, October 2. S. M. Johnson and A. G. Evans, "Probabilistic 1982. Aspects of High lemperature Failure," American Ceramic Society, Cincinnati, Ohio, May 1982. 39

c. Environmentally Affected Crack Growth in Engineering Materials*'

Robert O. Ritchie, investigator

Introduction. The objective of this program 1. ON THE LOAD RATIO DEPENDENCE OF FATIGUE is to examine mechanical and microstructural fac THRESHOLDS* tors involved in the micromechanisms of environ mentally influenced fatigue crack growth. Models S. Suresh and R. 0. Ritchie have been developed for the premature closure of cracks at ultralow growth rates approaching the A study was made of the influence of load threshold stress intensity &K0 for no crack ratio R on fatigue crack propagation and threshold growth, where the driving force for crack exten (iKp) behavior in 2-l/4Cr-lMo steel tested in dis sion is limited by the wedging action of corro tilled water, moist air, and dry hydrogen gas. sion debris and rough fracture morphologies The dependence of AK0 on load ratio was found to (oxide-induced and roughness-induced crack clos be far less marked in aqueous compared to gaseous ure, respectively, Fig. 1). In the past year, environments, where AK0 decreased sharply with such concepts havis been used to interpret fatigue increasing R. Based on Auger measurements of under variable amplitude loading and crack growth crack face oxidation and crack closure measure behavior in aqueous and viscous environments, and ments using ultrasonics, such results were attri to develop new fatigue resistant microstructures. buted to oxide-induced closure. Significant

Plosti city-Induced Oxide-Induced Roughness-Induced Closure Closure

*W)X (XT ^P*^

^^sf^< Km in

AK = K^ flK,'eff " "™x ^min eff

Fig. 1. Schematic illustration of mechanisms of fatigue crack closure relevant to growth rate behavior at near-threshold levels.

fiKeff is the effective stress intensity range (i.e., local near-tip crack driving force), given by the difference between the maximum

stress intensity (Kmax) and the stress intensity at closure of the

crack (Kci). For closure to be effective, Kc\ must exceed the minimum stress intensity in the cycle (Kmin)- (XBL 823-8161)

corrosion deposits and hence closure are only 4. MECHANISMS OF FATIGUE CRACK GROWTH UNDER developed at low load ratios in the gaseous VARIABLE AMPLITUDE LOADING* environments because of "fretting oxidation" induced by mechanical closure. In the more 5. Suresh and R. 0. Ritchie oxidizing water environments* crack face oxide debris form at all load ratios because of thermal New mechanistic interpretations for fatigue mechanisms which make closure, and hence AK0 crack growth retardation because of load excur values, much less dependent upon the load ratio. sions were developed based on a microroughness induced closure model. Analyses for the reduc * * * tions in effective driving force for crack advance following overloads were based on mech i'Brief version of LBL-H280 Rev. anisms of crack blunting, branching and closure, compressive stresses, and fracture morphology. It was argued that retarded crack growth is 2. INFLUENCE OF VISCOUS ENVIRONMENTS ON FATIGUE effectively governed hy mfcromechanisms of near- CRACK GROWTH* threshold crack growth, thus permitting quantita tive estimates of the local effective driving J.-L. Tzou, S. Suresh, and R. 0. Ritchie force to be computed.

The influence of viscous environments * * * (dehumidified silicone and paraffin oils) has been examined for fatigue crack growth in A542-3 tBrief version of LBL-14482. steel. Above ~10-5 mm/cycle, crack growth rates in oil were an order of magnitude slower than in either moist air or dry hydrogen gas. Conversely, below ~10-6 mm/cycle in the near-threshold regime, growth rates were an order of magnitude faster in 1982 PUBLICATIONS AND REPORTS oil. Such contrasting behavior was attributed to three competing mechanisms specific to oil en Refereed Journals vironments, namely (a) suppression of moisture- induced hydrogen embrittlement, (b) minimization 1. R. 0. Ritchie and S. Suresh, "Some Considera of crack flank oxidation and hence oxide-induced tions on Fatigue Crack Closure at Near-Threshold closure at near-threshold levels, and (c) develop Stress Intensities Due to Fracture Surface Mor ment of enhanced closure from the hydrodynamic phology," Met. Trans. .13A, 937 (1982); LBL-13836. wedge effect of a viscous medium within the crack. 2. S. Suresh and R. 0. Ritchie, "Mechanistic Dis similarities Between Environmentally Influenced * * * Fatigue Crack Propagation at Near-Threshold and Higher Growth Rates in Lower Strength Steels," +Brief version of LBL-15780. Metal Science 16, 529 (1982); LBL-13585.

3. S. Suresh and R. 0. Ritchie, "A Geometric 3. FATIGUE RESISTANT MICROSTRUCTURES IN Model for Fatigue Crack Closure Induced by DUAL-PHASE STEELS Fracture Surface Roughness," Met. Trans. 13A, 1627 (1982); LBL-13837. V. Dutta, S. Suresh, and R. 0. Ritchie +4. R. 0. Ritchie, F. A. McClintock, The incentive was to develop a ferritic- H. Nayeb-Hashemi, and M. A. Ritter, "Mode III martensitic microstructure in a Fe/2Si/0.1C si?el Fatigue Crack Propagation in Low Alloy Steels," with superior resistance to near-threshold fatigue Met. Trans. 13A, 101 (1982). by promoting crack path meandering and consequent roughness-induced crack closure. Three micro- +5. M. A. Ritter and R. 0. Ritchie, "On the structures (yield strength 600 MPa) were examined, Calibration, Optimization and Use of D.C. Elec namely, (a) a fine fibrous martensite in a ferrite trical Potential Methods for Monitoring Mode III matrix (obtained by intermediate quenching), Crack Growth in Torsionally-Loaded Samples," (b) a coarse martensite with continuous ferrite Fatigue Eng. Mater. Struct. _5, 91 (1982). (obtained by step quenching), and (c) a fine glob ular martensite along ferrite boundaries (obtained +6. H. Nayeb-Hashemi, F. A. McClintock, and R. 0. by intercritical annealing). It was found that Ritchie, "Effects of Friction and High Torque on the threshold was significantly higher (at &K0 Fatigue Crack Propagation in Mode III," Met. R = 0.05) in the step-quenched and intercritical Trans. _13A, 2197 (1982). annealed structures (16.7 and 19.4 MPa^fiT, respec tively) compared to the intermediate quenched *7. M. Kurkela, G. Frankel, R. M. Latanision, structure (AK = 10.6 MPat-fif), as a direct conse 0 S. Suresh, and R. 0. Ritchie, "Influence of quence of the rougher crack path in the former two Plastic Deformation on Hydrogen Transport in microstructures. 2-l/4Cr-lMo Steel," Scripta Met. .16, 455 (1982). 41

s8. J. F. McCarver and R. 0. Ritchie, "Fatigue sure Vessels, ASTM Special Technical Publication Crack Propagation Thresholds for Long and Short 755, ASTM, Philadelphia, Pennsylvania, 1982, Cracks in Rene 95 Nickel-Base Superalloys," Mat. p. 49. Sci. Eng. 5^, 63 (1982); LBL-13453.

9. A. K. Vasudevan and S. Suresh, "Influence of Corrosion Deposits on Near-Threshold Fatigue Invited Talks Crack Growth Behavior in 2XXX and 7XXX Series Aluminum Alloys," Met. Trans. 13A, 2271 (1982). 1. S. Suresh and R. 0. Ritchie, "On the Load Ratio Dependence of Near-Threshold Corrosion 10. S. Suresh, "Crack Growth Retardation due to Fatigue Growth," 111th Annual Meeting of AIME, Micro-Roughness: A Mechanism for Overload Dallas, Texas, February 1982. Effects in Fatigue," Scripta Met. 16, 995 (1982); LBL-144B3. 2. M. Kurkela, S. Suresh, R. M. Latanision, and R. 0. Ritchie, "tttects of Plastic Deformation on 11. S. Suresh and S. Bahadur, "Evaluation of Hydrogen Permeation," 111th Annual Meeting of Polymers as Lubricants in the Extrusion of Alumi AIME, Dallas, Texas, February 1982. num," J. Lubrication Tech., Trans. ASME 104, 552 (1982). 3. R. 0. Ritchie, "Non-Linear Fracture Mechanics: Uses and Limitations," Sandia National Laborator 12. S. Suresh, I. G. Palmer, and R. E. Lewis, ies, Livermore, California, April 1982. "Effects of Environment on Fatigue Crack Growth Behavior of 2021 Aluminum Alloy," Fatigue Eng. 4. R. 0. Ritchie, "Influence of Material Micro- Mater. Struct. 5_ 133 (1982). structure on Fatigue and Fracture," San Jose State University, San Jose, California, May 1982. LBL Reports 5. R. 0. Ritchie, "Fatigue Crack Propagation in 1. S. Suresh and R. 0. Ritchie, "On the Mode III," Rockwell International Science Center, Influence of Environment on the Load Ratio Thousand Oaks, California, May 1982. Dependence of Fatigue Thresholds in Pressure Vessel Steel," LBL-14280 Rev. 6. R. 0. Ritchie, "Environmental Effects on Fatigue Crack Propagation," Rockwell International 2. S. Suresh and R. 0. Ritchie, "A Model for the Fatigue Symposium, Science Center, Thousand Oaks, Contribution to Plasticity-Induced Fatigue Crack California, May 1982. Closure from Residual Compressive Stresses," LBL-14405. 7. P. K. Liaw and R. 0. Ritchie, "Influence of Gaseous Environment on Near-Threshold Crack Growth 3. J. A. Wasynczuk, R. 0. Ritchie, and G. Thomas, Behavior in Steels," International Congress on "Effects of Microstructure on Fatigue Crack Growth Technology and Technology Exchange, Pittsburgh, in Duplex Ferrite-Martensite Steels," LBL-14891. Pennsylvania, May 1982.

4. W. J. Salesky, R. M. Fisher, R. 0. Ritchie, 8. R. 0. Ritchie, "Microstructural Modelling for and G. Thomas, "The Nature and Origin'of Sliding the Prediction of Fracture Toughness," Exxon Wear Debris from Steels," LBL-15059. Research and Engineering Company, Linden, New Jersey, June 1982. 5. S. Suresh, "Micromechanisms of Fatigue Crack Growth Retardation Fallowing Overloads," 9. R. 0. Ritchie, "Application of Fracture LBL-14482. Mechanics to Fatigue Crack Propagation," University of California Extension Program, Other Publications Berkeley, California, June 1982 and Exxon Education Center, Florham Park, New Jersey, *1. R. 0. Ritchie and S. Suresh, "Effects of December 1982. Crack Flank Oxide Debris and Fracture Surface Roughness on Near-Threshold Corrosion Fatigue," 10. R. 0. Ritchie, "Physical Basis for Fracture in Atomistics of Fracture, edited by R. M. Toughness," University of California Extension Latanision and J. Pickens, Plenum Press, New Program, Berkeley, California, June 1982. York, 1982. 11. R. 0. Ritchie, "Elastic-Plastic Fracture 2. R. 0. Ritchie, S. Suresh, and P. K. Liaw, "A Mechanics," U.S. Steel, Monroeville, Pennsylvania, Comparison of Environmentally Influenced Near- July 1982. Threshold Fatigue Crack Growth Behavior in High and Lower Strength Steels at Conventional 12. R. 0. Ritchie and S. Suresh, "Mechanics and Frequencies," in Ultrasonic Fatigue, edited by Physics of the Growth of Short Cracks," plenary J. M. Wells, 0. Buck, L. D. Roth, and J. K. Tien, lecture to 55th Specialists Meeting of AGARD TMS-AIME, Warrendale, Pennsylvania, 1932, p. 443; Structural and Materials Panel, Toronto, Canada, LBL-13571. September 1982.

*3. S. Suresh, G. F. Zamiski, and R. 0. Ritchie, 13. R. 0. Ritchie, "Crack Closure Mechanisms "Fatigue Crack Propagation Behavior of 2-l/4Cr-lMo During Near-Threshold Fatigue Crack Growth," Steels for Thick Wall Pressure Vessels," in Appli Cockburn Engineering Center, University of cation of 2-l/4Cr-lMo Steels for Thick Hall Tres^ Toronto, Canada, September 1982. 42

14. S. Suresh and R. 0. Ritchie, "A Geometric tion to ASTM E24.04.06 Task Group on the Growth Model for Fracture Surface Induced Crack Closure," of Short Cracks, San Francisco, California, TMS-AIME Fall Meeting, St. Louis, Missouri, December 1982. October 1982. 23. R. 0. Ritchie, F. A. McClintock, and 15. R. 0. Ritchie. F. A. McClintock, and H. Nayeb-Hashemi, "Mode III Fatigue Crack Growth H. Nayeb-Hashemi, "Mode III Fatigue under under Combined Torsional and Axial Loading," Combined Loading," TMS-AIME Fall Meeting, St. International Symposium on Biaxial/Multiaxial Louis, Missouri, October 1982. Fatigue, San Francisco, California, December 1982. 16. R. 0. Ritchie, "New Mechanise of Corrosion 24. S. Suresh, "Plane Strain Closure Phenomena," Fatigue," General Motors Research Laboratories, Southwest Research Institute, San Antonio, Texas, Warren, Missouri, October 1982. February 1982.

17. R. 0. Ritchie, "Metal Fatigue: Ways of 25. S. Suresh, "Influence of Oxide Deposits on Slowing Down the Growth of Fatigue Cracks," ASM Fatigue Thresholds," University of Houston, Fall 1982 Educational Seminar, University of Texas, February 1982. Califnrnia, Berkeley, California, October 1982. 26. S. Suresh, "Fatigue Crack Closure: New 18. R. 0. Ritchie, "Analytical Framework for Mechanistic Interpretations and Implications," Linear Elastic Fracture Mechanics Methods," Exxon University of Southern California, Los Angeles, Education Center, Florham Park, New Jersey, California, May 1982. December 1982. 27. S. Suresh, "Micromechanisms of Crack Growth 19. R. 0. Ritchie, "Brittle Fracture Mechanisms Retardation Following Overloads, Parts I & II," and Phenomenology," Exxon Education Center, TMS-AIME Fall Meeting, St. Louis, Missouri, Florham Park, New Jersey, December 1982. October 1982.

20. R. 0. Ritchie, "Short Fatigue Cracks," kestinghouse Research and Development Center, * * * Pittsburgh, Pennsylvania, December 1982. •fyork supported in part by the Division of Energy 21. R. 0. Ritchie, "Role of Oxide-Induced Crack Conservation, U.S. Department of Energy under Closure in Corrosion Fatigue," invited presenta Contract No. EX-76-A-01-2295, TO 51. tion to ASTM E24.04.05 Task Group on Fatigue *Work supported in part at MIT by the Office of Crack Growth Rate Testing in Aqueous Environments, Basic Energy Sciences of the U.S. Department of San Francisco, California, December 1982. Energy under Contract No. DE-AC02-79ER10389. Swork suppoi'ted in part by National Science 22. R. 0. Ritchie and S. Suresh, "Fatigue Crack Foundation through the Center for Materials Growth of Short Cracks: Limitations Based on Science and Engineering, MIT, under Contract No. Microstructural Considerations," invited presenta DMR-78-24185. 3. Physical Properties

a. Interfaces and Ceramic Microttruclum*

Joseph A. Pask, Investigator

Introduction. The purpose of this work is to Au oxide layer. The contact angle was lower (7") advance basic understanding of the nature of due to a higher YSV (surface energy of Au) re interfaces (primarily those between dissimilar sulting from the absence of adsorbed oxygen on Au. materials, e.g., metals and ceramics), particu larly in terms of bonding and adherence. This In air, glass had a contact angle of 2-3* and understanding is critical in the development of adhered strongly to Pt because of tie dissolution composites, protective coatings, glass/ceramic to of a Pt oxide layer on the Pt surface. In vacuum metal seals, and 1n the reduction of corrosion at adherence was poor due to absence of adsorbed interfaces. The work involves studies of thermo oxygen. ^The contact angle, however, varied from dynamics and kinetics of reactions at interfaces 58 to 73* depending on the absence or presence of and of wetting and spreading of liquids. adsorbed carbon on the surface; adsorbed carbona ceous material reduces YSV Another objective in this work is to advance the understanding of the factors that play roles Oxygen is chemisorbed on Ag, Au, and Pt in air. in the development of desired microstructures in Although the surface oxides do not grow in thick ceramic materials, with and without a liquid ness, the amounts are sufficient to saturate the phase. This understanding depends on a knowledge glass at the interface since the solubilities of of the interfacial phenomenon from a thermo the precious metal oxides in glass are very low; dynamics point of view and of the mass transport also, interfacial saturation is sufficiently mechanisms during sintering. maintained, since diffusion gradients are small because of the low oxide concentrations.

1. WETTING AND REACTIONS IN.THE LEAD BOROSILICATE GLASS-PRECIOUS METAL SYSTEMS1' 'Brief version of LBL-156H. V. K. Nagesh, A. P. Tomsia, and J. A. Pask 2. THE SILICA-ALUMINA SYSTEM* Sessile drop experiments of lead borosilicate glass on Ag, Au, and Pt were performed in air, J. A. Pask vacuum, and helium at 700"C. This system is one of the more'important The gl^s spread on Ag in the presence of systems in ceramic oxide materials technology, oxygen, and v&ry strong adherence develooed. The but considerable confusion still exists in the driving force for spreading was provided by the nature of the phase equilibrium diagram. It has reduction of interfacial energy caused by a reac been indicated that difficulties are due t-i the tion between Ag oxide formed on the Ag surface fact that alumino-silicate liquids can be readily and SiO? in the glass. A low contact angle supercooled and supersaturated. A liquid that, (2-12"C) was observed for vacuum conditions and on cooling, would normally precipitate the crys good adherence developed. The adherence was due tal CX-AI2O3 can be easily supercooled in the ab to the saturation of the interface with Ag oxide sence of nuclei of 0-AI2O3 before the mullite as a result of a redox reaction between PbO in crystallizes. Mullite growing under these condi the glass and the Ag, indicated by a loss of Pb tions is capable of accommodating larger amounts from the glass. In 1 atom helium, adherence was of AI2O3, i.e., it has a larger solid solution poor because of the absence of the redox reaction, range. Mullite grown isothermally by chemically caused by suppression of any Pb vapor evolution interdiffusion has a narrower solid solution that would be formed; this absence also effects range. Procedures in the preparation of specimens an increase in y i (solid-liquid Interfacial in this system are thus critical and misinterpre energy) and the contacs t angle (5-48"). tations of experimental data have occurred in published papers, stable and metastable phase equilibria have been identified in the With Au, the contact angle was 18" and good a Al203-SiOj system. adherence was observed in air because of the dis solution of the Au oxide layer on the Au surface by the glass at the interface. In vacuum, the adherence was poor because of the absence of an t.Brie f version of LBL-14678.

1982 PUBLICATIONS AND REPORTS 8. S. M. Johnson and J. A. Pask, "Role of Impurities on Formation of Mullite from Kaolinite Kefereed Journals and Al203-Si0? Mixtures," Bull. Am. Ceram. Soc. 61, 838-842 (1982); LBL-13062. 1. S. H. Johnson, J. S. Moya, and J. A. Pask, "Influence of Impurities on High-Temperature 9. S. T. Tso and J. A. Pask, "Reaction of Fused Reactions of Kaolinite," J. Am. Ceram. Soc, Jj5_, Silica with Hydrogen Gas," J. Am. Ceram. Soc. 65, 31-35 (1962); LBL-11949. 457-460 (1982). —

2. M. 0. Sacks and J. A. Pask, "Sintering of LBL Reports Mullite-Containing Materials: I. Effect of Composition," J. Am. Ceram. Soc. Jj5, 65-70 1. D. J. Miller, "Liquid Phase Densification of (1982); LBL-11857-1/2. Titanium Carbide-Nickel Composites," Ph.D. thesis, LBL-13580. 3. M. D. Sacks and J. A. Pask, "Sintering of Mullite-Containing Materials: II. Effect of 2. A. P. Tomsia, F. Zhang, and J. A. Pask, Agglomeration," J. Am. Ceram. Soc. ^5, 70-77 "Wetting and Reactions in Glass/Non-Precious (1982); LBL-11857-2/2. Metal Alloy Systems," LBL-13847.

4. 1. Nurishi and J. A. Pask, "Sintering of 3. K. Wada, A. P. Tomsia, and J. A. Pask, a AIoOo-Amorphous Silica Compacts," Ceramics "Kinetics of Glass/Metal Reactions," LBL-13848. Internatlc-;. 8, 57-59 (1982); LBL-12457. 4. P. L. Flaitz, "Some Aspects of Liquid Phase 5. A. P. Tomsia, Z. Feipeng, and J. A. Pask, Sintering of Alumina," Ph.D. thesis, LBL-13849. "Wetting Behavior in the Iron-Silver System," Acta Met. 30, 1203-1208 (1982); LBL-13390. 5. J. A. Pask, "Current Understanding of Stable and Metastable Phase Equilibria and Reactions in

6. S. T. Tso and J. A. Pask, "Reaction of the Si02-o Al203 System," LBL-14678. Glasses with Hydrofluoric Acid Solution," J. Am. Ceram. Soc, 65, 360-362 (1982); LBL-12800. 6. W. M. Kriven and J. A. Pask, "Solid Solution Range and Microstructures of Melt-Grown Mullite," 7. S. T. Tso and J. A. Pask, "Reaction of LBL-14679. Silicate Glasses and Mullite with Hydrogen Gas," J. Am. Ceram. Soc. 65, 383-3B7 (1982), 457-460; 7. V. K. Nagesh and J. A. Pask, "Wetting of LBL-12»«2. Nickel by Silver," LBL-16023. b. High Temperature Reaction**

Alan W. Searcy, Investigator

Introduction. The first of the following arti- the relation of Wulff. The model predicts round cles initiates a series of theoretical and ex ing of edges and corners of kinds that are not perimental papers planned on surface thermodynam allowed by the Wulff relation and predicts that ics and related topics of adsorption-vapor equi quasispherical equilibrium crystals can have librium and of the kinetics of surface processes. anisotropic surface-free energies. The model The article explores the assumption that the most appears to be consistent with experimental ob stable forms of small crystals or cavities are servations, and it provides a useful framework the forms for which the Zr\jGj is a minimum, where for analysis of whether unstable crystal or ni is the number of atoms with excess free ener cavity shapes will evolve into stable or metas gies Gi by virtue of being near a surface. This table forms. Some crystals and cavities that model predicts forms of crystals that are some have been assumed to have equilibrium shapes times more stable than fiose governed by the Wulff instead have metastable shapes. relation. This relation, a-j/hi = aj/hj..., where a] is the surface tension of a stable face * * * at a distance h^ from a common center, has been accepted as governing crystal and cavity shapes for 80 years. The new relation recognizes that tBrief version of LBL-14716, to appear in J. spherical crystals need not have isotropic spe Solid State Chem. cific-surface-free energies and permits better 1. J. W. Gibbs, The Collected Works. Vol. 1: understanding of the kinetics of surface-shape Thermodynamics, Longmans, Green, New York, 1931, changes and of the persistence of metastable p. 320. shapes. The remaining articles describe recent 2. G. Wulff, Z. Krist. 34, 449 (1901). studies directed toward the long-range objectives of generating reliable experimental data for at- composition reactions and formulating a coherent 2. EFFECTS OF PARTICLE SIZE AND POWDER BED SIZE theoretical framework for analyzing the kinetics ON CALCITE DECOMPOSITION RATESt and thermodynamics of such reactions and of the physical properties, thermodynamics, and kinetics Mun Gyu Kim, Alan W. Searcy, and Dario Beruto of the solid products of decomposition reactions. The kinetics of endothermic decomposition reactions of the type AB(s) = A{s) + B(g) have been so poorly understood that reviewers have 1. THE EQUILIBRIUM SHAPES OF CRYSTALS AND OF often described them as reversible, yet analyzed CAVITIES IN CRYSTALS'1' them in terms of kinetic models that implicitly assume complete irreversibility. Beruto and Alan W. Searcy Searcyl proved that decomposition of calcite single crystals is highly irreversible; the rate It has been believed that a proof of Gibbs'1 of CO2 escape is only ~10~5 times the rate possi rules out rounded equilibrium surfaces for parti ble for a reversible reaction.2 But calcite pow cles or cavities in particles, unless the surface der beds give unexpected apparent equilibrium tensions (or specific surface free energies) in pressures only -lO-4 times the thermodynamic the rounded surfaces are essentially isotropic. equilibrium pressure for the reaction. This It has also been believed that an inescapable study was undertaken to determine the influences corollary of Gibbs' proof is that equilibrium of particle size, sample size, and particle pack surfaces must obey the relation deduced by Wulff,2 ing densities on decomposition rates. No detailed oi/hj = oj/hj = ..., where o, is a surface ten systematic study of these questions had been pre sion and h-j is the distance of the surface from a viously reported. common center. high-purity. natur?l-calcite single crystals In this article, surface free energies are as were c»it and separated into sized fractions with sumed to be the sum of the excess free energies particles in the range 74-90 urn, 0.5-0.6 mm, of bonding of molecules in or near the surface, 1.0-1.4 mm, and 4 mm average cross sections. and the stabie form of a crystal or cavity is as Samples of ~3 ym, 5-10 urn, and 10-20 urn average sumed to be the form that makes the sum of these cross sections were separated from commercial excess free pnergies a minimum. calcite powders by means of an ultrasonic fine sieve. Regardless of particle size, the powders When only plane surfaces are allowed, this had rhombohedral shapes, which implies that the model predicts the same shapes for crystals as individual particles were single crystals. Sam-

*This work was supported by the Oirector, Office of Energy Research, Office of Basic Energy Sci ences, Materials Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. 46

pies of various particle sizes were decomposed at 3. POSSIBLE HETASTAB1LITY OF HgO RESULTING FROM 610'C or 670*C in vacuum in alumina cells. For THE DECOMPOSITION OF Mg(OH) * calcite of >0,5 mm cross section, weight losses 2 were directly proportional to sample heights from Thomas A. Reis, David J. Meschi, and Alan W. 2.5 mm to 14.4 mm: Decomposition of these beds Searcy of large crystals is irreversible, as found for single crystals.! In contrast, the flux-per- Measurements of the equilibrium HpO decom unit cross sectional area of the exposed powder position pressure for the reaction Mg(0H)2(s) = bed surface was independent of sample height and MgO{s) + HjOfg) were made by Giauque and Archi packing density (Fig. 2.1). For these powder bald! at 453dn d 485 K using a static manomet- beds, near-equilibrium pressures are established ric technique, and later by Kay and Gregory? in when the CO2 flux from the bed is ~10-4 times that the same temperature range by means of a kinetic for true equilibrium. Neither XRD studies nor Knudsen cell method. The pressures measured by TEM studies show products of calcite decomposition Kay and Gregory were only -10-4 times those of other than normal CaO. It is suggested nonethe Giauque and Archibald. Theoretically, possible less that the COj pressure in the bed may be explanations for the discrepancy are that vacuum characteristic of an equilibrium between CaC03 decomposition yields MgO of (surprisingly) high and an unstable CaO(CaC03)x phase which decomposes surface free energy or a metastable solid, either irreversibly when its layer thickness is only a a metastable form of MgO or an MgOxMg(OH)2 phase few nm. TEM experiments in controlled CO2 at where x > 0. Such a metastable product would have mospheres could test this hypothesis. to have a heat of formation -48 KJ/mole of MgO present higher than that of normal MgO. X-ray studies show no evidence of a product other than normal MgO.3 We report here calorimetric meas urements designed to test for metastable product •lUrief version of LBL-15236. formation. 1. D. Beruto and A. W. Searcy, J. Chem. Soc. Faraday Trans. I 70, 215 (1979). 2. G. F. Knutsen, A. W. Searcy, and D. Beruto, Samples of Mg(0H)2 were prepared in the same J. Am. Ceram. Soc. 65, 219 (1982). manner as that used by Giauque and Archibald* and then decomposed to varying degrees in vacuo at ~300*C, some in open crucibles, most in Knud sen cells under conditions like those of Kay and Gregory. Products were then dissolved in 1M HC1 10 1 1 1 and the heats of solution measured. The heat of 1 1 solution of any residual undecomposed Mg(0H)2 was subtracted from the measured values to give - the heats of solution of the MgO products. • • 670°C Figure 3.1 is a plot of the results in which 8 _0 O •" the molar enthalpy of solution of the MgO is plotted against the mole fraction of MgO in the • So.nple. To represent the equilibrium form of MgO, D A we used samples annealed at 1000*C for 10 hr or • more. The dashed line represents the value for & this standard material. Although there is con 6 O siderable scatter in the data, the deviations Particle from the dashed line appear to be random and size, Sample height,mm amount to 12 kj mole-1 at most; much less than _2.5 10.0 14/L - the ~48 kj mole-1 required by the hypothesis. ~3 O A D 4 - 10-20 • A m - GaA^0O*C/2.l0"5tixr Knudien , s open cell ld -20.5 mm] H( id'1.80 mm - Cell 1 • closed cell ldM 610 °C • Eturt-3-0-9.0 kJ/maies n 2 * 0 i• • 4 7.11.4 Kcol/rwK MgO •

___L .___. 0 1 1 ! ! 1 1 i -iT*^t 0.2 0.6 1.0 1.4 1 _ * T 3 Pocking Density (g/cm ) * 1f """""" •

Fig. 2.1. Jef vs packing density with a con XM,0 stant distance (=1 cm) between the top of sample cell and the top of sample, where Jef is the Fig. 3.1. Enthalpies of solution of MgO as a weight loss per unit cross-section area of sample function of the mole fraction of MgO in the sam cell per unit time. (XBL 825-5764) ple. (XBL 823-2078) 47

Any metastable solid product must he a transient phase present in quantities too small to be de tected either by x-ray diffraction measurements or by these calorimetric measurements. A TEM search for a transient phase is planned. * * *

tBrief version of LBL-15725. 1. W. F. Giauque and R. C. Archibald, J. Am. Chem. Soc. 56, 561 (1937). 2. E. Kay and N. W. Gregory, J. Phys. Chem. 62, 1079 (1958). — 3. T. A. Reis, D. J. Meschi, and A. W. Searcy, MMRD Annual Report for 1978, LBL-8580, p. 114.

4. CONFIRMATION OF BlriODAL PORE SIZE DISTRIBUTION IN CaO FROM CALCITE DECOMPOSITION1"

Dario Beruto, Luigi Barco, and Alan W. Searcy

In the 1981 Annual Report we reported that surface areas and pore volumes in the CaO com Fraction Decomposed, oC, pacts formed by decomposing a calcite single crys tal in steps, with measurements made on the same sample at liquid N2 temperatures before it was Fig. 4.1. Volume of <0.1 wm pores, a's, sum of reheated for an additional fractional decomposi large and small pore volumes i's, and total sur tion of the calcite present. These data sup face areas o's, as functions of fraction of CaO ported the suggestion of Powell and Searcy1 that formed by CaC03 single crystal decomposition in a duplex pore structure is formed, but the sur vacuum. (XBL 832-8442) face areas of the CaO when decomposition was com plete was only -90 m2/g, compared to ~120 m^/g expected from Powell and Searcy's results. The 5. GAS FLOW THROUGH POROUS BARRIERS: THE 02-Pt, discrepancy is shown here to be a consequence of CO-Pt SYSTEMS*" thermal cycling between the decomposition temper ature and liquid N2 temperature. The volume of Jeffrey N. Farnsworth and Alan W. Searcy >0.1 urn pores, which had been calculated by dif ference, has been confirmed by means of mercury For gases that show physical adsorption on porisimetry. surfaces of porous barriers, surface diffusion has been found to contribute measurably to bar The uppermost line of Fig. 4.1 is the theoret rier permeation only if temperatures are low, ical pore volume calculated from fae sample mass usually less than room temperature, and if pore and its external dimensions as a function of ex dimensions are <0.1 um. But recently Jacobson tent of reaction. The points marked a and b are and Searcy1 showed that surface diffusion makes the total volumes calculated from Ng condensa measurable contributions to transport of LiF, NaF, tion in pores too small for Hg porisimetry meas and NaCl vapors through alumina. This study was urements and from Hg porisimetry measurements in undertaken to determine if gases that chemisorb pores too large for Hi condensation measure with energies comparable to those of the alkali ments. The lowest line shows the N2 condensa halide vapors, as measured by &Hads/RT, where

tion data. Agreement of points a and b with the iHacjs is the enthalpy of adsorption, would also theoretical curve confirms the duplex pore struc show high surface diffusion fluxes on porous Pt ture. The middle curve shows that the specific metal barriers. surface area of CaO is independent of extent of reaction (in disagreement with results reported from other laboratories), and the specific sur A manifold system contained pressure monitor face areas found are -120 m2/g, as reported by ing devices, allowed access for the gases studied, Powell and Searcy. and also served as a reservoir. A valved mullite tube connected the manifold system to the plati num porous barrier, which was mounted in a vacuum furnace. Fluxes through the barrier were calcu lated from the recorded pressure drop with time. +Brief version of LBL-13882 Rev. 1. E. K. Powell and A. W. Searcy, J. Am. Ceram. For a particular gas, the flux measured (J) Soc. 65, C42 (1982); LBL-11207. may be compared with the flux of a standard gas, 48 such as helium (Jj,), in which Knudsen flow is * * * the only transport mechanism. A ratio 0/0|( pro vides a measure of the importance of surface dif +Brief version of LBL-15724. fusion. The quantity J/J^ is plotted vs AHa(js/RT 1. N. S. Jacobson, "The Diffusion of Gases in (Fig. 5.1) for the systems in this and the alkali Capillaries," Ph.D. thesis, LBL-13227. halide-alumina study.* In the range of 4Ha(js/RT values for which the alkali halide-alumina systems show significant surface diffusion, the 02-Pt, C0- 1982 PUBLICATIONS AND REPORTS Pt systems do not. The importance of surface dif fusion relative to vapor phase diffusion varies Refereed Journals with radius-*. The studies with ~5 ym pores in platinum permit the conclusion that diffusion of 1. G. F. Knutsen, A. W. Searcy, and D. Beruto, O2 and CO on Pt is less important than that of "Effects of LiCl on the Rate cf Calcite Decompo NaF or LiF on alumina. The data show that sur sition," J. Am. Ceram. Soc. 65(4), 219-222 (1982); face diffusion depends on the kinds of chemisorp- LBL-12043. tion bonds. 2. E. K. Powell and A. W. Searcy, "Surface Areas and Morphologies of CaO Produced by Decomposition of Large CaC03 Crystals in Vacuum," J. Am. 14 Ceram. Soc. 65(3), C42-C44 (1982); LBL-11207 Rev.

> He/Pt 3. A. W. Searcy and D. J. Heschi, "Electronic Ceramics in High-Temperature Environments, J. Am. >02/Pt •LiF/AU), Ceram. Soc. 65(4), 216-218 (1982); LBL-11821. «CO/Pt d 6 LBL Reports

1. S. L. Roche, "Thermal Decomposition of Magnesium and Calcium Sulfates," Ph.D. thesis, LBL-14303.

2. D. J. Meschi and A. W. Searcy, "Catalysis of MgSOi) Decomposition by FejOs," LBL-14393.

3. A. W. Searcy, "The Equilibrium Shapes of Crystals and of Cavities in Crystals," to be published in J. Solid State Chem., LBL-14716.

+4. D. Beruto, L. Barco, and A. W. Searcy, "Re arrangement of Porous CaO Aggregates During Cal cite Decomposition in Vacuum," LBL-14901. NaCI/AI 0U- # 22 3 5. M. G. Kim, "Effects of Particle Size on Cal cite Decomposition," M.S. thesis, LBL-15236. t) 10 20 30 40 50 60 * * *

AHads/RT ^Supported in part by the Division of Materials Fig. 5.1. Surface diffusion as a function of the Sciences, Office of Basic Energy Sciences, U.S. normalized heat of adsorption for gas/solid sys Oepartment of Energy and in part by the Italy-U.S. tems. (XBL 832-1193) Exchange Program of CNR (Italy) and NSF. 49

c. Structure-Property Relationships in Semiconductor Materials"

Jack Washburn, Investigator

Introduction. The aim of the program is to undertake basic research leading to a more com plete understanding of the structure-sensitive electrical properties of semiconductor materials. An attempt is made to choose topics for investi gation that have a relation to state-of-the-art technology and to carry on joint research with the semiconductor industry where possible.

The current activity of the program is in three major areas:

1. Applications of high resolution lattice imaging electron microscopy to the study of interfaces, 2. Effects of ion damage in silicon and gallium arsenide, and 3. Improvement of experimental and analytical techniques for the characterization of fig. 1.1. HRTEM image of a djurleite domain defects in semiconductors. formed in a basal chalcocite film after aging in air at room temperature for four days. Some of the individual research topics briefly (XBB 829-7601) described in this report can be related to more than one of the major areas. CU20S12 four-vacancy clusters has been developed. These clusters order simultaneously into the 1. THE MECHANISM OF DEGRADATION OF Cu?S-CdS superstructure o< djurleite, leaving the common SOLAR CELLS AS REVEALED BY HIGH RESOLUTION h.c.p. sulfur lattice intact. ELECTRON MICROSCOPY*

T. Sands, R. Gronsky, and J. Washburn ^Extended abstract of LBL-15063; also presented The major factor preventing the production of at the Sixteenth IEEE Photovoltaic Specialists inexpensive and efficient Cu2S-CdS thin film Conference, San Diego, CA, September 1982; in solar cells is the inherent instability of the press. p-type copper sulfide layer. This layer can act as an efficient adsorber-emitter only if the pre dominant phase is chalcocite (CU2S). A small 2. AN APPLICATION OF HIGH RESOLUTION LATTICE amount of copper loss because of non-optimum for IMAGING ELECTRON MICROSCOPY TO A STUDY OF THE mation conditions, in-service oxidation, or elec- MECHANISM OF THE CRYSTALLINE TO AMORPHOUS tromigration under load results in the formation TRANSFORMATION1" of djurleite (CU1.97S) and a corresponding re duction in cell efficiency. This study addresses J. Washburn, C. Murty, and R. Gronsky the problem of determining the microscopic mecha nism of the chalcocite-djurleite transformation so th-t methods to produce more stable layers for The mechanism of the crystal to amorphous device configurations may be systematically transformation during ion damage in silicon has explored. been investigated using high resolution lattice imaging electron microscopy. It was found that sharp interfaces exist between amorphous and High resolution transmission electron crystalline regions in partially amorphous sil microscopy (HRTEM) of copper sulfide thin films icon. Simulated lattice fringe images for in has revealed the formation and growth character creasing Frenkel pair concentrations were istics of coherent djurleite domains in chalcocite generated which suggest that a sharp change in during aging in air at room temperature. Speci lattice fringe visibility implies a sharp change fically, chalcocite/djurleite interfaces are in structure. abrupt and tend to lie in planes which minimize the lattice mismatch between the two phases (see There is enough evidence from conventional Fig. 1.1). A model for the transformation involv transmission electron microscopy that amorphous ing the clustering of copper vacancies into silicon, even restricting consideration to those structures produced by radiation damage, is in reality a class of materials with structures *This work was supported by the Director, Office ranging from something like the idealized random of Energy Research, Office of Basic Energy network models to something considerably less Sciences, Materials Sciences Division of the U.S. random. It is likely that the mechanism of for Department of Energy Under Contract No. mation of "amorphous" silicon may be signifi DE-AC03-76SF00098. cantly different at low and high temperature. 50

fluence which shows that the shrinkage of amor * * * phous zones was not because of specimen heating. Previous experience also suggests that the rise +Brief version of LBL-14873. in temperature of the specimen could not have approached the 450*C necessary to get thermal 3. EFFECT OF RECOIL IMPLANTED OXYGEN ON THE regrowth of amorphous regions. DEVELOPMENT OF SECONDARY DEFECTS IN MOS TEST WAFERS' The experiment suggests that the formation of amorphous material during ion damage can involve N. R. Wu, P. Ling, D. K. Sadana, J. Washburn, and a competition between two processes: M. I. Current* 1) formation of new amorphous zones, and The growth or annihilation of secondary defects can be profoundly affected by surrounding impurity 2) shrinkage of amorphous zones that are still complexes and the annealing ambient'. When high surrounded by crystalline material. dose implantations are done through screen-oxfdes into Si, high concentrations (>10'1 cm-3) of re At low temperatures (

The experimental program was designed to relate to the general processing conditions of an +Brief version of LBL-15487. all-implanted MOS device fabrication technology. The implantation was carried out into (100) Si wafers with As ion beams of 4 to 12 mA for doses 5. EFFECT OF TEMPERATURE AND DISPLACEMENT DAMAGE 4 to 7 x 1015 cnr2 at 100 or 120 keV followed by ON THE GROWTH OF AMORPHOUS IAYERS IN SILICON^ annealing at 1,000"C for 30 minutes in N2 or O2 or their combination. The TEM results from D. K. Sadana, J. Washburn, P. F. Byrne,* and the above wafers revealed that interstitial dis N. W. Cheung* location loops of irregular shape were present beneath the surface in two discrete layers. It One of the undesirable effects of ion was found that annealing out of the loops is implantation is the temperature rise of semi accelerated in the presence of Og in the anneal conductor wafers during the implantation. This ing atmosphere. This finding is in contradiction rise is caused by dissipation of kinetic energy to many previous papers, in which the injection of the ion beam before coming to rest in the of Si interstitials from the advancing Si02/Si wafer. If the wafer being implanted with beam interface into the bulk has been proposed. Under currents of greater than several hundred pA has a these conditions, the loops should grow rather poor thermal contact with its mounts in the than shrink as observed in the present study. implantation chamber, nonuniform heating of the wafer results. The effect of implantation tem perature on the formation of amorphous layers in Si during ion implantation has therefore been systematically investigated by transmission elec + Brief version of LBL-15491. tron microscopy (Fig. 5.1). The mechanisms of Now at Trilogy, Cupertino, CA. in-situ annealing suggested by J. Washburn et al.l have been further clarified. In order to inves tigate the effect of displacement damage on 4. IN-SITU OBSERVATIONS OF MeV ELECTRON BEAM in-situ annealing, the sample of Fig. 5.1a was INDUCED.CRYSTAL GROWTH INTO AN AMORPHOUS LAYER IN subsequently implanted at higher temperature SILICON1" (RT-400°C). It was found that at 200*C or ?hove isolated binall amorphous zones (<50 A diameter) J. Washburn and D. K. Sadana embedded in the crystalline matrix near the two amorphous/crystalline interfaces dissolved into Deep buried amorphous layers were created in the crystal, but the width of the 100% amorphous (100) Si by 11 MeV As implantation. The effect layer was not appreciably^affected by further of 1.2 MeV electron irradiation at the upper and implantation at up to 200°C. lower interfaces of the buried layer was investi gated on thin cross-section specimens prepared for transmission electron microscopy. It was It is suggested that small amorphous zones found that amorphous zones shrink at both inter surrounded by crystalline material can undergo faces; however, the effect was most pronounced at radiation induced shrinkage at temperatures the near-surface interface where amorphous zones ^100°C where elementary point defects are mobile. would have been expected to be surrounded by crystalline material over a wider region. The experiment was repeated at high and low beam tBrief version of LBL-15489. current in order to estimate the effect of beam *Dept. of Electrical Engineering, U. C. Berkeley. heating. The result was almost the same for the 1. J. Washburn et al. , LBL-14873,- Nucl. Instruro. two beam currents for comparable total electron Meth., in press. 0.3//FTI Fig. 5.1. The effect of implantation temperature on the formation of an amorphous layer in P implanted (111) Si. Dose: 3 x 10.14 cm-2; Energy: 120 keV; implantation temperature: a) LN, b) RT, and c) 100'C. (XBB 820-9449A)

6. A MODEL FOR REDISTRIBUTION OF PHOSPHORUS 7. DIFFRACTION EXTINCTION CONDITIONS FOR SILICON DURING ANNEALING OF HIGH DOSE ION IMPLANTED AND OTHER MATERIALS WITH DIAMOND GLIDE PLANES+ SILICON* P. Ling, R. Caron, and J. Washburn D. K. Sadana and J. Washburn Although {200} Bragg reflections are One of the reasons for widespread usage of kinematically forbidden in diamond cubic and arsenic as the n-type dopant in most implanted spinel (i.e., Fd3m) structures, they often appear silicon devices despite its relatively low elec in electron diffraction patterns because of dynam trical activity at high doses is that it has ical effects. In <100> and <012> diffraction predicable redistribution behavior on post im patterns (200) spots cannot arise from multiple plantation annealing. On the other hand, phos diffraction within the zeroth Laue zone. Our phorus doping can produce higher electrical analysis shows that these spots can arise from activity, but its redistribution behavior on double diffraction which must involve both higher annealing is anomalous. In the present investi and lower order Laue zones. We call this higher- gation, ion implantation of phosphorous into lower Laue zone pair-double diffraction {HLLZPDD). silicon has been investigated by cross-sectional transmission electron microscopy and secondary We derived the dynamical extinction conditions ion mass spectrometry. for these Fd3m structures using the method devel oped by Gjfinnes and Moodie.* We showed that for In the case of high dose (>10^5 cm-2) implanta the Fd3m diamond glide plane perpendicular to the tion, ifi which the implanted region becomes amor x-y plane and passing through (0,1/8,0), structure phous and extends to the surface, it has been factors are related by F (fi,k,l) = i (h + k + 1) F observed that the P atoms in the initially amor (h,k,l). For the four-fold screw axis perpendicu phous region do not redistribute on subsequent lar to the x-y plane and passing through (0,1/4,0), annealing while the P atoms below the initial the relation is F (h,k,l) + i (h + k + 1) amorphous crystalline interface diffuse rapidly F(k,h,l). In electron diffraction patterns, these into the Si substrate. The carrier concentration spots often appear even when the extinction con profiles from the annealed samples were found to ditions are met. This is because of the non- follow the atomic profiles almost exactly over parallel nature of the incident electron beam. the depth range extending from the surface to where the original amorphous/crystallii••» inter Reasons are given for spinel crystals having face existed. However, in the deeper regions, stronger {200} reflections than diamond cubic the electrical activity was found to be dependent crystals in <00J> diffraction patterns. Firstly, on the annealing temperature. The different be spinel has a denser reciprocal space than diamond havior of phosphorus in the initially amorphous cubic, so there are more possibilities for dif and crystalline regions has been explained by a fraction, contributing more dynamical intensity model which assumes that during recrystalliza- to {200} spots. Secondly, among allowed reflec tion, the moving amorphous/crystalline interface tions, a greater portion of spinel reflections incorporates both impurity as well as silicon can contribu' ) to HLLZPDD which results in {200} atoms on substitutional sites. The P atoms in spots. the deeper regions are believed to redistribute via an interstitial diffusion mechanism at low temperatures (<750*C) and eventually occupy sub stitutional sites at higher temperatures (_>800*C). tBrief version of LBL-15490. 1. J. Gj0nnes and A. F. Moodie, Acta Cryst, J_9_, 65 +Brief version of LBL-15488. (1965). 52

1982 PUBLICATIONS AND REPORTS Materials Characterization, Alfred University, New York, August 16-18, 1982, in press, LBL-15085. Refereed Journals 4. C. S. Murty, "Crystalline to Amorphous Trans 1. T. D. Sands, J. Washburn, and R. Gronsky, formation in Silicon," Ph.D. thesis, LBL-14923. "High Resolution Observations of Copper Vacancy Ordering in Chalcocite (CujS) and the Transfor 5. J. Washburn, C. Murty, D. K. Sadana, P. Byrne, mation to Djurleite (Cuj 97 to Cui 94 S),H R. Gronsky, N. Cheung, and R. Kilaas, "The Phys. Stat. Sol. (a) 72/551 (19825; LBL-13746. Crystalline to Amorphous Transformation," Nucl. Instrum. Meth., in press, L3L-14873. 2. D. K. Sadana, J. Washburn, and G. R. Booker, "Recrystallization of Buried Amorphous Layers in 6. D. K. Sadana, N. R. Wu, J. Washburn, M. I, P+ Implanted Si and Associated Electrical Current, A. Morgan, D. Reed, and M. Maenpaa, "The Behavior," Phil. Mag. B 46, 611 (1982); LBL-14889. Effect of Recoiled 0 on Damage Regrowth and Electrical Properties of Through-Oxide Implanted 3. D. K. Sadana, J. Washburn, T. Zee, and R. G. Si," Nucl. Instrum. Meth., in press, LBL-15086. Wilson, "Effect of 0 on Cr Redistribution in Ion Implanted GaAs," J. Appl. Phys. 53, 6413 (1982); 7. 0. K. Sadana, J. Washburn, and C. W. Magee, LBL-13527. "Substitutional Placement of Phosphorus in Ion Implanted Silicon by Recrystallizing Amorphous 4. P. F. Byrne, N. W. Cheung, and D. K. Sadana, Crystalline Interface," J. Appl. Phys., in press, "Mega-Volt Arsenic Implantation into Si," Thin LBL-15488. Solid Films 95, 363 (1982). 8. D. K. Sadana, J. Washburn, P. F. Byrne, and 5. M. Maenpaa, T. F. Kuech, M-A. Nicolet, S. S. N. W. Cheung, "Damage and In Situ Annealing Dur Lau and D. K. Sadana, "The Heteroepitaxy of Ge on ing Ion Implantation," Defects in Semiconductors Si: A comparison of Chemical Vapor and Vacuum (Materials Research Society Symposium), Vol. 4, Deposited Layers," 0. Appl. Phys. 5_3_, 1076 (1982). in nress, LBL-15489.

6. M. Maenpaa, L. S. Hung, S. S. Lau and D. K. Invited Talks Sadana, "Epitaxial Reordering of Ion-Irradiated

NiSi2 Layers," Thin Solid Films 87, 277 (1982). 1. 0. K. Sadana, "Profiling of Ion Implanted Semiconductor Surfaces by TEM, RBS, SIMS and 7. P. F. Byrne, N. W. Cheung and D. K. Sadana, Electrical Measurements," Microelectronics Center "11 Mel/ As Implantation into Si," Appl. Phys. of North Carolina, Research Triangle Park, Lett. 41, 537 (1982). Raleigh, North Carolina, December 7, 1982. 2. 0. K. Sadana, "Structural, Electrical and LBL Reports Compositional Characterization of Interfaces 1n Ion Implanted and Processed Semiconductors," pre 1. M. Current and D. K. Sadana, "Materials sented at the Naval Research Labs., Washington, Characterization for Ion Implantation," VLSI D.C., November 5, 1982. Electronics: Microstructure Science, Vol. 6, Chapter 7, edited by N. G. Einspruch and G. L. 3. D. K. Sadana, "Ion Implanted Generated Larrabee, Academe Press, in press, LBL-15014. Microdefects and Their Electrical Properties," National Semiconductor, Santa Clara, CA, June 4, 2. T. D. Sands, R. Gronsky, and J. Washburn, 1982. "High Resolution Study of the Chalcocite (CU2S)-

Djurleite (Cui#g7S) Transformation in CU2_XS Thin 4. D. K. Sadana, "Materials Characterization for Films," presented at the Sixteenth IEEE Photo Ion Implantation," U.C. Extension Course, Hyatt voltaic Specialists Conference, San Diego, CA, Rickey Hotel, Palo Alto, CA, April 20, 1982. September 1982, in press, LBL-15063. 5. D. K. Sadana, "Recrystallization of Amorphous 3. D. K. Sadana, "Cross-Sectional Transmission Layers in Ion Implanted Si and GaAs and Associated Electron Microscopy of Semiconductors," 18th Electrical Effects," University of Southern University Series on Ceramic Science Advances in California, Los Angeles, CA, March 12, 1982. 53

d. Chemical ProperttM and Processing of Refractory Ceramics* Lutgard C. De Jonghe, Investigator

1. PROCESSING OF CERAMICS 2. STRUCTURE AND NONSTOICHIOMETRY OF CALCIUM ALUMINATES+ Lutgard C. De Jonghe Herbert Schmid and Lutgard C. De Jonghe Many ceramics and refractories are prepared by the sintering of component oxides. A variety of Calcium aluminates form the basis of many re chemical reactions and microstructural develop fractory and high temperature cements. The phase ments occurs during the densification of such relationships in this system have been studied by mixed powders, including the transient or perma several investigators; the most recent phase dia nent formation of compounds and liquids. These grams now include C3A, CA, CA2, and CAK(C = CaO; reactions may significantly affect the densifica A = A1 0 ). tion rates and the microstructural developments 2 3 of the ceramic body. In the present work, ceramic alloys were prepared by reacting dense, polycrystalline The first step in studying such reactions has alumina with a liquid of approximately eutectic been the study of the densification of a simple composition, at 1530*C, for about 4 hours. The pseudo-binary system: MgF2 + CaF2- This system reaction zone was then examined by transmission exhibits a eutectic at 918°C and does not form electron microscopy and by x-ray microanalysis in compounds. Dialotometric measurements and an analytical transmission electron microscope. examination of microstructures of power mixtures The foils show planar defects in the CA5 phase containing up to 5 wt% CaF2 showed that CaF2 sig similar to those found in sodium beta and beta nificantly enhanced densification of MgF2 well aluminas.* The observed planar defects are syntactic intergrowths whose structure could be below the eutectic temperature. This result described by the formalism developed by Braun.3 could be attributed to an increase in the solid Planar defects were found on (00.1) planes (Fig. state grain boundary transport rate, caused by 2.1). The lattice fringe images of faulted areas the presence of small amounts of calcium exhibit variations in spacings where the faults fluoride.1 The significant increase in solid occur. In large CA6 grains, syntactic inter- state grain boundary transport rates below the growth regions could be found with a periodicity eutectic temperature of a binary system should significantly larger than that of the CAs matrix. be a general phenomenon that could be usefully Non-periodic arrays of syntact intergrowths were exploited in ceramic processing, since it could also found (Fig. 2.2). lead to enhanced densification without the abnormal grain growth caused by the presence of active liquid phases. Toward the boundaries of some large grains, irregularities in the fringe images could be found. Examples of the various types of irregu The system under investigation at present is larities are shown in Fig. 2.3. They include Ca0-Al203. Enhanced pre-eutectic densification irregular intergrowths, Fig. 2.3a; gradual dis rates, around 1350°C> are not observed in the sys appearance of fringe contrast, Fig. 2.3b and 2.3c; tem, but they are observed in, e.g., CU2O-AI2O3. or switching to a different fringe spacing, Fig. The decrease of the densification rates of AlgOa 2.3c. Micro-x-ray analysis revealed that these caused by CaO are thought to be due to rapid and fringe irregularities were linked to a decrease extensive formation of very stable, intergranular in the CaO contents. compounds such as Ca0-{Al2O3)6- The reactions between CaO and AI2O3 are described below in more detail. The observation indicated that the crystal lography of CAX compounds may be described in a manner analogous to that of the barium hexaferrites.2

+Brief version of LBL-14291. 1. S. C. Hu and L. C. De Jonghe, LBL-12849, 1. L. C. De Jonghe, J. Mat. Sci, 12, 497 (1977). April 1982. 2. P. B. Braun, Philips Res. Rep,~T2, 491 (1957).

Fig, 2.1, Lattice fringe images and selected area diffraction pattern of faulted CA5. (a) BF image showing 00.2 fringes of the CAg phase, and Fy intergrowths. (b) BF image showing 00.1 fringes of the CAg

phase with Fx and F„ intergrowths. (XBB 824-3406)

CzMi b 13.8 rtt%CoO Fig. 2.2. (a) Non-periodic Fy intergrowth form ing a transition zone between the M(CA5) and the

V(C2A7) phase, (b) Schematic representation of

CA6 {M) the local CaO content in the Y-M transition zone 8.1 III II Dili III imaged in (a). (XBB 824-3978)

Fig. 2.3. (a) Irregular lattice fringe images due to terminating M intergrowths in a W matrix. The energy-dispersive x-ray spectra of

the marked regions are also shown, (b) Terminating F2n intergrowths in a transition zone between a CA5 and CaO-free region, (c) Transi tion of M phase to y alumina. (XBB 824-339S) 55

3. WORK IN PROGRESS model is under development that takes into account interface oxygen diffusion and CO-CO2 conversion Whisker Growth During CO/CO,, Reduction of catalysis to predict the morphology of the reduc Iron-Bearing Oxides" tion product.

Mei Chang and Lutgard C. De Jonghe 1982 PUBLICATIONS AND REPORTS

When iron-bearing oxides such as cobalt ferrite LBL Reports are reduced with CO/CO2 mixtures, profuse forma tion of metallic whiskers may be observed. It is 1. H. Schmid and L. C. De Jonghe, "Structure and found that the whisker diameter is determined by Non-Stoichiometry of Calcium Aluminates," the overall reaction rate and can be changed to a LBL-94291. larger or smaller diameter by changing the total gas pressure during the reduction. This indicated 2. S. C. Hu and L. C. De Jonghe, "Pre-Eutectic that the whisker morphology is a consequence of Densification in MgF2-CaF2," LBL-12849. the difficulty of removing oxygen from under the advancing metal oxide interface. This difficulty Invited Talks is related to the rate at which CO is converted to CO2 at the whisker base. This conversion is 1. L. C. De Jonghe, "Densification in MgF2-CaF2," dependent on the presence of impurities that may Fifth International Meeting on Modern Ceramic catalyze or inhibit the CO to COj reaction. A Technologies, Lignano, Italy, June 1982. 56 e. Structure and Electrical Properties of Composite Materials*

Robert H. Bragg, Investigator

Introduction. The purpose of this work is to 50 HTj.HRS understand how the properties of hard carbons and , soft carbons are related to their structure. The o BRAGG and MEHROTRA I5E7MIM. 3 latter become physically,soft when heated above • SO. R I. 9"C/M1N. 0 about 2000°C; whereas the former, typified by glassy carbon (GC), are little affected by heating above 3000"C. Soft carbons are fairly well un derstood, but basic knowledge concerning hard carbons is scant. In this work GC is used as a model hard carbon because it is obtained as chem ically pure (i.e., elemental carbon) monolithic solid suitable for a wide variety of measurements of physical properties. Results to date, show that GC is coi.posed of laths or ribbons of turbo- stratic graphite-like carbon layers that enclose a closed pore volume of about 30%. Whereas soft carbons are semimetallic conductors, GC has elec trical properties like those of amorphous semi conductors. At low measurement temperatures, in material heated below 2000°C, there is evidence of one-dimensional electrical conduction.

1000 2000 3000 1. DENSITY OF HEAT-TREATED GC + TEMPERATURE (*C> Bhola N. Mehrotra and Robert H. Bragg Fig. 1.1. Comparison of average linear dila tion of GC with values calculated from in-situ Polycrystalline carbons swell irreversibly measurements. (XBL 827-6012) about 1« when heated above their processing temp erature, but in GC it reaches 15% for samples heated to 275Q°C. It is important to understand 5.0 1 1 r— this swelling in carbons because it can be dele AS RECEIVED GC(SO.R.U terious in structural applications. It may be caused by internal gas pressures,>• but a ther mal stress mechanism has also been proposed.2 Measurements of density, weight, length, and vol ume changes were made on samples heated in inert atmosphere in the range 1000-2700°C for three hours. Density changes caused by hydrostatic compression up to 1550 MPa (225,000 psi) were also measured.

Results: density decreases are mostly due to volume increases; dimensional changes (Fig. 1.1—open circles) are macroscopically isotropic and are not reversed by hydrostatic pressures. In-situ measurements (Fig. 1.2) show that during initial heating relief of residual stresses oc curs, irreversible dilation occurs above 1000°C, and the upper cooling curve is followed there 1000 2000 3000 after in thermal cycling. This interpretation TEMPERATURE ("C) predicts the closed circles in Fig. 1.1. A de Fig. 1.2. In-situ thermal expansion measurements tailed analysis shows that some swell .ng is on GC. Room temperature to 2700'C and return. caused by gas pressures, but most of it is be (XBL 827-6011) cause of thermal stress.

+Brief version of LBL-15072, to be published in J. Mat. Sci. 1. D, B. Fischbach and M. E. Rorabaugh, High *Tnis work was supported by the Director, Office Temperature and High Pressure 9_, 199 (1977). of Energy Research, Office of Basic Energy 2. R. H. Bragg and S. 8ose, "Thermally Induced Sciences, Materials Sciences Division of the Density Changes in Glassy Carbon," 14th Biennial U. S. Department of Energy under Contract No. Carbon Conference, University Park, Pennsylvania, DE-AC03-76SFO0O98. June 1970, p. 189. 57

2. PORE GROWTH IN GLASSY CARBONt crystallite size on radial distribution functions. The principal investigator will be on sababatical Jeffrey Hoyt and Robert H. Bragg leave during January-June 1983. About three months will be spent at CNRS, University of During heat treatment of GC the specific sur Bordeaux, to do work on magnetic susceptibility face area, S/V, decreases with an activation en of GC. ergy of about 60 ± 10 kcal/mole.1 Host of the change is in S; thus, the internal pore structure of GC is coarsening. Another parameter to char acterize pores is the radius of gyration, Rg, a 1982 PUBLICATIONS AND REPORTS dimension analogous to the quantity in classical mechanics of physical bodies, but with electron Other Publications density replacing mass. Its geometrical interp 2 retation can be very ambiguous, but a kinetic 1. R. H. Bragg, "Is Graphitization the Result of study of Rg can reveal changes in average pore a Thermal Decomposition Reaction," 35th Pacific size, and possibly in pore size distribution. Coast Regional Meeting, American Ceramic Society, Seattle, Washington, October 26-28, 1982. Samples of GC were heated in pure argon or helium at 1600, 1800, 2100, and 25O0*C for times 2. D. F. Baker and R. H. Bragg, "Electrical Con ranging from 1 up to 48 hr. SAXS measurements ductivity in Glassy Carbon," 35th Pacific Coast were made using crystal monochromated CuKa ra Regional Meeting, American Ceramic Society, diation in an apparatus employing linear position Seattle, Washington, October 26-28, 1982. sensitive x-ray detection. The data were fitted to an expression in which R is related to the g 3. L. G. Henry and R. H. Bragg, "The Measurement temperature and a diffusion coefficient D. of Specific Surface Area and Pore Size in Some Ceramic Materials Using a Modified General Elec The results show the expected tl/3 depend tric (GE) Diffractometer," 35th Pacific Coast Re ence of Rg. The average Rg increases with gional Meeting, American Ceramic Society, Seattle, HTT with an activation energy of 51 ± 9 kcal/mole, Washington, October 26-28, 1982. compared with the value of 60 ± 10 kcal/mole de termined from S/V kinetics.^ These results 4. J. J. Hoyt and R. H. Bragg, "A Study of Pore nd strong support to the hypothesis that the Growth in Glassy Carbon Using Small Angle X-ray vacancy migration is the mechanism that governs Scattering," 35th Pacific Coast Regional Meeting, the coarsening of the pore structure. American Ceramic Society, Seattle, Washington, * * * October 26-28, 1982. 5. B. N. Mehrotra and R. H. Bragg, "Volume Ex +Brief version of L8L-14580. pansion and Weight Loss in Heat-Treated Glasslike 1. S. Bose and R. H. Bragg, Carbon 19, 289 Carbon (GC)," 35th Pacific Coast Regional Meeting, (1981). ~ American Ceramic Society, Seattle, Washington, 2. A. Guinier and G. Fournet, Small Angle Scat October 26-28, 1982. tering of X-rays, Wiley, London (1955).

LBL Reports 3. WORK IN PROGRESS 1. J. Hoyt, "A Study of Pore Growth in Glassy D. Baker is preparing three papers for publi Carbon Using Small Angle X-Ray Scattering," M. S. cation based on his Ph.D. dissertation, and also thesis, LBL-14580. concentrating on one-dimensionality and other anomalous aspects of electrical properties in GC. 2. B. N. Mehrotra, R. H. Bragg, and A. S. Rao, A collaboration has been initiated with Drs. "Effect of Heat Treatment Temperature (HTT) on James Rhyne and Jack Rush, Reactor Radiation Di Density, Weight, and Volume of Glasslike Carbon vision, National Bureau of Standards, to obtain (GO," LBL-15072, submitted to 0. Mat. Sci. neutron diffraction patterns of GC samples. Ef forts 1 ' determine the amount and bonding of hy 3. L. G. Henry and R. H. Bragg, "Comparative De drogen i GC were initiated in 1981 via a second termination of the Incoherent Scattering in Amor collaboration, with Professor Cary Macie^ at the phous Materials," LBL-15611. Regional Center for Nuclear Magnetic Resonance at Colorado State University, but the results thus 4. D. F. Baker and R. H. Bragg, "One-Dimension far have not been interpretable. Very recently, ality in Glassy Carbon," LBL-15445, submitted to a third collaboration has been initiated with Dr. Phys. Rev. Lett. J. D. Jorgensen, Neutron Scattering Group, Mater ial Science and Technology Division at Argonne National Laboratory, to obtain measurements of Invited Talks total neutron scattering cross section of GC where the sensitivity for hydrogen is very large. Kinetic studies of the loss of hydrogen from GC 1. D. F. Baker and R. H. Bragg, "Electrical are envisaged. Both L. G. Henry and B. N. Properties of C'assy Carbnn," International Sym Mehrotra are involved in this work. A. Pearson posium on Carbon: New Processing and Applica is doing a computer simulation of the effect of tions, Toyohashi, Japan, November 1-4, 1982, Ex tended Abstracts 2B08, p. 208, LBL-14938. 58

f. High Temperature Oxidation and Corrosion of Materials *

Introduction. The principal aim of this improve the scaling properties of alloys. While program is to establish mechanisms of materials there is no general consensus to explain the cause degradation in environments associated with the of this phenomenon, the evidence suggests that combustion of fossil fuels and relating these this improvement is because of the development of mechanisms to fundamental thermodynamic, kinetic, inwardly growing oxide pegs, which mechanically and metallurgical variables. A recent major key the scale to the substrate. Detailed observa achievement has been to establish the mechanism tions of different peg morphologies are used to by which certain active additions to heat- define the conditions and mechanisms of growth. resisting alloys improve the adherence of the protective scales. This is reported in article 1. Following standard preparation, samples were oxidized in static air at 1200"C. Specimen char Sulfur is a critical impurity present in almost acterization included optical and scanning elec all fossil fuels. Its presence in the gaseous tron microscopy, x-ray diffraction, and electron products of combustion can result in accelerated probe microanalysis. A deep etching technique, degradation of alloys. Article 4 demonstrates the based on partial dissolution of the alloy, was rapid diffusion of sulfur species down oxide grain employed to examine peg morphologies. boundaries at rates much higher than previously reported. Articles 5 and 6 are concerned with the Two distinct types of peg were identified based sulfur-induced hot corrosion which is due to the on morphological and growth criteria: formation of molten deposits on alloy surfaces. Class I. The growth of this peg type was Multiphase diffusional growth during aluminiz- observed on alloys forming external NiO scales ing, a thermochemical process by which AI is dif containing small additions of oxygen active ele fused into the surface of a material to improve ments and is illustrated in Fig. 1.1a. Growth is high temperature oxidation resistance, is controlled by solute and/or oxygen diffusion in described in article 7. Finally, mathematical the alloy. It can be interpreted by classical models have been developed to predict and inter internal oxidation theory.1 pret the concentration profiles developed when Ni-Co alloys are oxidized to produce a single Class II. The growth of this peg type was phase oxide; these are described in article 8. observed in Al203-forming alloys (Fe-10%A1) with small additions of Hf and is illustrated in Fig. 1.1b. Its development can be rationalized by short circuit diffusion in an host scale. 1. MECHANISM OF PEG GROWTH AND INFLUENCE ON SCALE ADHESION* * * A

Horoun M. Hindam and David P. Whittle *Brief version of LBL-15039. 1, J. H. Swisher, "Oxidation of Metals and It has been known, for many years, that minor Alloys," edited by D. L. Douglass, American additions of oxygen active elements (e.g., Ca, Sc, Society for Metals, Metals Park, Ohio, 1971, Y, Zr, Ce, Hf, etc) or their oxide dispersions p. 235.

*This work was supported by the Director, Office of Enercy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U. S Department of Energy under Contract IJo. DE-AC03-7GSF00098.

Dr. Whittle died in July 1982. This report has been prepared by Dr. Stephen Smith. Since Dr. Whittle's death, Dr. J. Stringer of the Electric Power Research Institute has been acting as technical advisor, pending the appointment of a full-time successor. 59

Fig. 1.1. Oxide peg morpholo (a) Ni-2Hf alloy and (b) Fe-lOAl-lHf alloy. (XBB 831-996)

2. MICROSTRUCTURE AND GROWTH OF PROTECTIVE spread of growth rates observed for Cr203 scale

Cr203 AND AI2O3 SCALES AT HIGH TEMPERATURE* does encompass unacceptedly high rates (Fig. 2.1).

David P. Whittle and Naroun M. Hindam Breakdown of the protective scale, especially by mechanical spallation, is critically dependent Current understanding of the complex inter on the details of the microstructure, and the relationships between growth kinetics, scale ability of active element or oxide dispersion ad microstructure, and scale adhesion for 0203 and ditions to modify this is of clear technological AT2O3 protective scales has been critically importance. However, without a clear understand reviewed. ing of the mechanism, it is unlikely that the maximum benefit of these effects can be achieved. A close interaction between the above param The work described in the later part of this re eters was demonstrated, although this is probably view points to the right direction. not of major importance in terms of the growth rate of the protective oxide. This is especially true in the case of AI2O3, since growth at the fastest observed rate does not correspond to a *Brief version of LBL-14296. major loss in material in many instances. The 60

and associated with, the microstructurally segre gated yttride phase (C03Y) at a-e boundaries. The peg morphology in the Hf-alloys, which form no segregated Hf-containing phase, is not associ ated with the alloy phaso br idaries, and no sheaths were found.

These observations in conjunction with previous observations of sheaths in vapor-deposited coat ings are considered as evidence of an indirect influence of microstructure on the pegging pro cess. A zone depleted of the e-phase was observed below the scale in all oxidized alloys. Simple observations and calculations were made with a view to elucidate the pegging mechanism; however, these are not entirely conclusive and additional work was suggested.

*Brief version of LBL-14668. 1. See for example, D. P. Whittle, "High Temper ature Corrosion of Aerospace Alloys," AGARO Con ference Proceedings No. 120, p. 174-199, 1972.

4. SULFUR DIFFUSION IN OXIDE GRAIN BOUNDARIES*

Frank C. Yang and David P. Whittle As part of a study examining sulfur transport ) 1000 in oxides, we have fully oxidized iron coupons TEMPERATURE, and then exposed them to an H2-IOZ H2S mixture at 870°C for 1 min. Fig. 2.1. Summary of reported parabolic rate constants for the growth of O2O3 on binary Cr- Figure 4.1 shows the impact fracture cross containing alloys. (XBL 821-7735) section of the scale. The left side of the micrograph shows a region of intergranular frac ture, whereas the right side shows a transgranular fracture area. Figures 4.1b and c are Auger electron maps of the same area. Consideration of 3. THE INFLUENCE OF ALLOY MICROSTRUCTURE ON these pictures clearly shows that sulfur is pres AI2O3 PEG MORPHOLOGIES IN CoCrAl ALLOYS AND ent only along the grain bound;ries of the scale COATINGS* and is rapidly removed via argon sputtering into the grain. Even in this very short exposure, Rajendra U. Pendse and David P. Whittle sulfur penetrated completely through the 1-mm- thick sample. A comparative study of Al203-peg morphologies in oxidized Co-lOCr-llAl-lHf as-cast and heat- These results indicate an effective diffusion treated alloys *as carried out with a view to coefficient of at least 10~4 cm? sec~l. This is examine the role of alloy/coating microstructure considerably higher than reported for the diffu in the pegying process. The fundamental aspects sion of sulfur ^n wustite. Whether the value of selective oxidation have been developed in implied by the present results represent grain several earlier papers.* boundary diffusion or gaseous transport through fine pores at the oxide grain boundaries remains The Y-containing alloys exhibited internal in question. AI2O3 formation in two distinct zones. An upper zone of relatively short branched pegs directly connected to the scale and a lower zone of mor phologically different sheaths developing along, *Brief version of LBL-14594. 61

5. THE EFFECTS OF SO2 and SO3 ON THE Na2S04 INDUCED CORROSION OF NICKEL*

Ajaya K. Misra and Oavid P. Whittle

Hot corrosion in gas turbines operating in marine environments is attributed to the deposi tion of Na2S04 on the blade and vane surfaces. The temperature of operation and SO3 concentration in the turbine atmosphere determine the corrosion behavior of the component. The effects of SO2 and SO3 in the environment on the hot corrosion of Ni in the temperature range 750 to 950*C have been studied.

Below the melting point of Na2S0A (880'C), rapid corrosion takes place by the formation of a Na2S04-NiS04 melt that penetrates the oxide layer and reaches the metal surface where further dis solution takes place. At temperatures above the melting point of Na^SO^, degradation occurs be cause of a dissolution reprecipitation mechanism.

In all cases the final corrosion product is dependent upon, and varies with, the SO2 content in the atmosphere. (It is probable that the sig nificant species in the atmosphere was SO3, but this was not directly treasured.) At low SO2 con centrations at low temperatures, an intermixed oxide and sulfide scale with a layer of sulfide at the scale/metal interface are formed. Increas ing the PSO2 content results in the formation of a thick intermixed oxide-sulfide layer above a NiO layer; once again sulfide is found at the scale- metal interface.

•Brief version of LBL-14597.

6. EFFECTS OF CHLORIDES ON Na2S04-INDUCED HOT CORROSION OF MCrAl*

Ajaya K. Misra and David P. Whittle

Chloride-containing species are often present in a typical gas turbine atmosphere. The major species are NaCl and HC1.1 The effects of HC1 and a Na2S0i)-NaCl deposit on the hot corrosion of Ni and Co base alloys in the temperature range 750-850°C have been studied.

In this investigation, the corrosion experi ments are carried out under very severe conditions at the level of HC1 and the amount of Na2S04-NaCl deposit are much higher than would occur under actual turbine operating conditions. The results do indicate the role of the chloride-containing species in the degradation of the alloys tested.

*Brief version of LBL-14388. 1. F. J. Kohl, C. A. Stearns, and G. C. Fryburg, in Metal-Slag Gas Reactions and Processes, edited by I. A. Foroulis and W. W. Smeltzer, Electro- chemical Society, Princeton, NJ, 1975, p. 649. 62

7. MULTIPHASE DIFFUS10NAL GROWTH DURING 8. HIGH TEMPERATURE OXIDATION OF Ni-Co ALLOY ALUMINIZING* Peggy Y. Hou and David P. Whittle Hilary C. Akuezue and David P. Whittle Hi and Co form a near ideal solid solution^ Aluminizing is a thermochemical process by over their entire composition range above 900*C. which Al is diffused into the surface of a materi The objectives of this project is to use this al to improve, for instance, its high temperature relatively simple system to gain a quantitative oxidation resistance. An aluminized sample, on understanding of binary alloy oxidation. exposure to high temperature oxidizing environ ments, forms a protective AI2O3 scale. Ni Co alloys in the composition range 1-80X Co are being studied in high- and low-oxygen activi Six aluminizing packs with different Fe-50 w/o ty atmospheres. Kinetic data are measured thermo- Al/Pure Al ratios were used to aluminize Fe-20 Cr gravimetrically, and diffusion profiles are samples at 850,900,950, and 1Q00°C. Mass change obtained using electron probe microanalysis. vs time curves were determined at all tempera Theoretical calculations make use of the transport tures. The Al and Cr profiles as a function of equations originally proposed by Wagner.* Diffu depth were determined using electron probe micro sion in the alloy is considered negligible when analysis on polished cross sections. oxidation occurs in high oxygen activity atmo spheres. However, cation transport in the scale Figure 7.1 shows etched cross sections of as well as diffusion in the alloy must be con specimens aluminized in various packs for 5 hr at sidered for oxidation in low-oxygen activity 900°C. This suggests that pack Al compositions atmospheres. Cation diffusion in the scale is affect the distribution of the aggregates and the solved using a total defect model developed by relative cepth of the consequent two-layered Whittle et al.2 diffusion zone and determines the interface mor phology. Near the terminal composition, the dif Theoretical calculations of Co concentration fusion path runs parallel to the Al line of the profiles in the scales oxidized under 1 atm Oj corresponding ternary phase equilibrium diagram, show good agreement with experimentally measured but near the a6/a5Fe+B2 Tine the diffusion paths data (Fig. fl.l). However, oxidation in the low- run parallel to the Cr line. This work is part oxygen activity environments, resulted in measured of an overall effort to use diffusion data and profiles that deviated from those predicted using kinetic data from aluminizing as well as phase this model. This is probably because of inward equilibria in the design of diffusional coatings anion transport leading to internal oxidation be for high temperature corrosion protection. coming more prevalent in low Pp, atmospheres, a factor not considered in the model.

T Brief version of LBL-15058. 1. C. Wagner, Corrosion Science 9_, 91 (1969). 2. D. P. Whittle, F. Gesmundo, and F. Viani, Oxid. Met. JJ>, 1-2, 81 (1981).

i^S^l^

Fig. 7.1. Cross sections of Fe-20Cr samples aluminized in various parts for 5 hr at 9Q0*C. (XBB 820-10998) 63

3. A. K. Hisra, D. P. Whittle, and W. L. Worrel, Microprobel ANH0.9wt%Co alloy "Thermodynamics of Molten Sulfate Mixtures," J. Electrochem. Soc. £, 8 (1982). analysis I • Ni-20.6wt% Co alloy - profiles I • Ni-38.4wt%Co alloy LBL Reports J o Ni-80 wt%Co alloy Theoretical cation profiles 1. D. P. Whittle and H. Hindam, "Microstructure and Growth of Protective Crj03 and AI2O3 Scales at High Temperatures," LBL-I4296.

2. H. Hindam and D. P. Whittle, "High Temperature Internal Oxidation of Dilute Ni-Al Alloys," LBL-14389.

3. H. Hindam and D. P. Whittle, "Evidence for the Growth Mechanisms of Cr203 at Low Oxygen Poten tials," LBL-14834.

4. H. Hindam and D. P. Whittle, "Microstructure, Adhesion and Growth Kinetics of Protective Scales on Metal and Alloys," LBL-15004.

5. H. Hindam and D. P. Whittle, "Mechanism of Peg Growth and Influence on Scale Adhesion," LBL-15039.

6. A. K. Misra and D. P. Whittle, "Effect of Chlorides on NagSO^ - Induced Hot Corrosion of MCrAl's," LBL-14388.

7. F. C. Yang and D. P. Whittle, "Sulfur Diffusion in Oxide Grain Boundaries," LBL-14594.

"0 0.2 0.4 0.6 0.8 1.0 8. A. K. Misra and D. P. Whittle, "The Effects of SO2 on the Na2S04 - Induced Corrosion of i Nickel," LBL-14597. Fig. 8.1. Comparison at theoretical and experi 9. H. C. Akuezue and D. P. Whittle, "Surface Al mental Co profiles in (Ni,Co)0 scales. Oxidized Composition During Pack Aluminizing—A Quantita at 1000'C in 1 atm Ox. (XBL 832-8037) tive Model," LBL-15058.

Invited Talks

1. D. P. Whittle and H. Hindam, Conference on Corrosion-Erosion-Wear of Materials in Emerging Fossils Energy Systems, Berkeley, California, January 1982.

1982 PUBLICATIONS AND REPORTS 2. H. Hindam and D. P. Whittle, "Characteriza tion, Amelioration and Mechanism of Scale Adhesion Refereed Journals to Metallic Substrates Subjected to Agressive En vironments," Canadian Metal Chemistry Conference, 1. H. Hindam and D. P. Whittle, "Corrosion Kingston, Ontario, June 1982. Behavior of Cr203 Former Alloys in H2/H2S/H2O Atmospheres," Corros.-NACE 38, 32 (1982). 3. H. Hindam and D. P. Whittle, "Mechanism of Peg 2. H. Hindam and 0. P. Whittle, "Peg Formation Growth and Influence on Scale Adhesion," Japanese by Short-Circuit Diffusion in AI9O3 Scales Con Institute for Metals, Third International Symposi taining Oxide Dispersions," 0. Electrochem. Soc. um on High Temperature Corrosion of Metals, Tokyo, 129, 1147 (1982). Japan, November 1982. g. Ceramic Interfaces* Andreas M. Glaeser, Investigator

Introduction. Numerous properties of ceramics controversy. One explanation is that (MgO) are strongly dependent upon the nature of the solute-boundary interactions reduce the grain microstructure. Consequently, successful fabri boundary mobility (relative to that in undoped cation of ceramics that meet design requirements material), and consequently produce conditions necessitates that the microstructural character favoring pore-grain boundary attachment and com istics (grain size, density, pore size, etc.) plete densification. The alternate explanation developed during processing and the stability of suggests that MgO additions enhance the pore the microstructure during subsequent use be mobility (relative to that in undoped material), understood and controlled. The grain size and thus promoting porp-grain boundary attachment and other microstructural characteristics are direct permitting theoretical density to be reached. ly or indirectly affected by the rate of grain Resolution of this controversy would constitute boundary motion. Thus control of microstructural an important first step in the development of a evolution during processing and degradation dur scientific basis for testing and selecting appro ing use requires that the grain boundary migra priate additives for other ceramic systems. tion rate be controlled. The focus of this program is to further our understanding of the In order to determine the effects of MgO factors that influence or control the nature of additions on pore and boundary mobilities, the the boundary migration process. solute-boundary interaction and pore-boundary interaction (in doped and undoped material) must The grain boundary migration rate in a be isolated and characterized. In the present material can be characterized in terms of a work, a small coarse-grained region is introduced parameter known as the boundary mobility, defined into an otherwise pore-Tree fine-grained MgO- as the boundary velocity per unit driving force. doped AI2O3 sample by means of a laser melting The grain boundary mobility is affected by inter technique. Coarse grains produced in this way, actions between the grain boundary and solutes, as well as those which develop naturally in the pores, precipitates, etc. Although reported material, are subject to a larger driving force boundary mobilities for a specific material may than the average sized matrix grains and thus differ by orders of magnitude at a particular coarsen at a substantially higher rate, consuming temperature, the nature of the interactions the surrounding matrix. Grain boundary migration responsible for these differences, and conse can be characterized by monitoring the growth quently their effects on microstructure develop rates of the coarse grains. Systematic variation ment, are poorly understood. The development of of a single microstructural characteristic (such an experimental technique* to permit these inter as the grain size, solute content, or volume actions to be isolated for high temperature fraction porosity), permits the effect of driving oxides has made possible an investigation of the force, solutes, or pores on boundary migration migration behavior of individual grain boundaries rates to be determined. To date, work has in theoretically dense MgO-doped A1203- focused on investigation of the solute-boundary interaction.

The growth rates of laser-introduced abnormal 1. A. M. Glaeser and J. C. Chen, J. Am. Ceram. coarse grains, naturally occurring coarse grains, Soc. 65 (7), (lf(82). and in so*e cases those of the finer matrix grains in MgO doped AI2O3 i.a-.-e been measured at temperatures from 1600-1900'C (Table 1.1). The 1. GRAIN BOUNDARY MOBILITY MEASUREMENTS IN growth rates of both types of coarse grains were MgO-DOPED A1 0 + generally spatially nonuniform, maximum and mini 2 3 mum mobilities differing by more than an order of Andreas M, Glaeser magnitude; minimum growth rates and hence bound ary mobilities were often too low to be measur When undoped AI2O3 is processed by able. A few cases of uniform boundary migration conventional powder processing techniques, a were observed; these occurred more frequently as porous, and often coarse grained material is the anneal temperature increased. The maximum produced. In contrast, small additions of MgO mobilities and other aspects of the migration permit preparation of fine grain size, theoretic behavior of the two types of coarse grains were ally dense material having superior optical and similar (Table 1.1) over the entire temperature mechanical properties. At present, the mechanism range investigated. The maximum observed mobil- by which MgO additions modify the course of ites in this study exceed those reported in pre microstructural evolution is still a subject of vious studies conducted on porous doped material and are comparable to those observed in porous undoped AI2O3. One possible interpretation of this result is that the maximum mobilities ob served do not reflect a Mg-boundary interaction, *This work was supported by the Director, Office i.e., that these boundaries have broken away from of Energy Research, Office of Basic Energy the segregated solute cloud. The observation Sciences, Materials Sciences Division of the that the maximum mobilities of coarse grains U. S. Department of Energy under Contract No. exceed that of the "average" matrix grains is DE-AC03-76SF00098. Table 1.1. Summary of Calculated Grain Mobilities.

Temp max max CO laser nucleated naturally (from grain (cm /dyne sec) nucleated growth rate

1600 3.0 x 10* 2.5 x 10"13 2.0 X 10~14 1700 -13 1.2 x 10~12 (not yet measured) 1800 2.3 x 10" 3.8 x 10"12 1.7 x 10~13 1900 1.4 X 10"1 (not yet measured)

consistent with this hypothesis and furthermore to MgO-Doped AljOl," J. Am. Ceram.Soc. 65_ (7), suggests that boundary breakaway may be the event C97 (1982); LBL-13800. that catalyzes abnormal grain growth. Synthesis of samples with varying MgO content is in pro gress; measurements of the concentration depend Invited Talks ence of both the maximum and average mobility should test the validity of the proposed inter 1. A. M. Glaeser, R. M. Cannon, and M. F. Yan, pretation of the data. "Effect of Solutes on Grain Boundary Migration," Pinual Meeting of American Ceramic Society, International Symposium on Grain Boundaries and +Brief version of LBL-15406 and J. C. Chen and Interfaces in Ceramics, Cincinnati, Ohio, May A. M. Glaeser, "Grain Boundary Mobility Measure 2-6, 1982. ments in MgO Doped AI3O3," 35th Pacific Coast Regional Meeting, American Ceramic Society, 2. A. M. Glaeser and J. C. Chen, "Technique for Measuring Grain Boundary Mobility in Ceramics," Seattle, Washington, October 26-29, 1982. 35th Pacific Coast Regional Meeting, American Ceramic Society, Seattle, Washington, October 1982 PUBLICATIONS AND REPORTS 26-29, 1982.

Refereed Journals 3. J. C. Chen and A. M. Glaeser, "Grain Boundary Mobility Measurements in MgO Doped AI2O3," 35th 1. A. M. Glaeser and J. C. Chen, "Technique for Pacific Coast Regional Meeting, American Ceramic Measuring Grain Boundary Mobility: Application Society, Seattle, Washington, October 26-29, 1982. 66 4. Engineering Materials

a. Abrasive* Erosive, and Sliding Wear of Materials*

lain Finnie, investigator

Introduction. The damage done by wear has critical tests have still to be made to confirm been estimated to represent about 6% of our gross some of the assumptions involved. national product. By contrast, about 0.02% of the national research dollar is invested in wear

research.! /\s a result, progress in understand ing wear has developed much less rapidly than in '''Brief version of R. Glardon and I. Finnie, ASME other areas of science and engineering. Most of J. Eng. Mat. Technol. 105, 36 (1983) and R. Glar our current knowledge of wear is based on empiri don and I. Finnie. ASM"FTJ. Eng. Mat. Technol. 105. cal tests that simulate the behavior of specific 31 (1983). components. This type of information is of little value in understanding the basic mechanisms of wear or in predicting the wear to be expected in 2. ABRASIVE WEAR* new applications. For this reason the purpose of the present work is to obtain a more detailed un Iain Finnie and S. Soemantri derstanding of wear mechanisms. In the period covered by this report, attention has been given to the sliding wear of dissimilar metals, abrasive Abrasive wear continues to be the predominant wear of metals, and the preparation of an overview wear problem in industry. The choice of materials to summarize the economic importance of wear, its for abrasive wear resistance is inadequately un various categories and the extent of our current derstood- A major problem is that different types knowledge. of abrasive wear may occur in service with dif ferent material properties governing wear resist * * * ance in these different regimes. During the past year we have studied different 1. E. Rabinowicz, Mech. Eng. 204, 62 (1983).f types of abrasive wear tests at ambient and ele vated temperature. Limitations of several test techniques have been observed, and the role of 1. SLIDING WEAR OF DISSIMILAR METALS many variables has been studied. In particular, the role of temperature in several types of Iain Finnie, Susan Chevez, and Remy Glardon abrasive wear tests has been investigated.

The traditional explanation of sliding wear, Conventional theories of abrasive wear have which was based on adhesion of contacting asper been shown to be inadequate for explaining exper ities, has been questioned in recent years. Our imental results. Our attempts to produce a more work in the past year confirmed that the accumu general approach are drawing on experience also lation of subsurface plastic deformation followed with erosive wear and hopefully will lead to an by crack initiation and propagation is the pri approach that unifies the erosive and abrasive mary mechanism of material removal in this type wear phenomenon. of wear. * * * Our research has followed two routes. One has involved the detailed investigation for five al '''Brief version of A. Misra and I. Finnie, ASME J. loys of the macroscopic and microscopic aspects Eng. Mat. Technol. 10A_, 94 (1982). of the surface and subsurface features of the damage produced by sliding wear. At the same time we have been developing a test to simulate 3. AN OVERVIEW OF WEAR sliding wear with a larger scale mechanical test. This involves loading specimens in combined com I. Finnie and A. McGee pression and shear with alternating loads. Because of the general neglect of wear research Preliminary indications are that the simple alluded to in the introduction, it was thought mechanical test provides considerable insight worthwhile to prepare a general review. This cov into the processes involved in sliding wear. A ers the economic importance of wear, the classifi model of sliding wear has been developed, but cation of wear into its different categories, and a brief summary of the state of knowledge on dif ferent aspects of wear.

*This work was supported by the Director, Office Our approach is to draw literature on the econ of Energy Research, Office of Basic Energy omic importance of wear from various sources and Sciences, Materials Sciences Division of the to attempt our own classification of wear into U. S. Department of Energy under Contract No, different categories. There is a danger in over DE-ACO3-76SF00098. simplification when subdividing any field, yet one 67 has to compartmentalize wear in order to develop analyses of individual mechanisms. In reviewing * * * different areas of wear, our emphasis has been on 1. I. Finnie, Mechanisms of Wear, Proceedings of unsolved problems and areas that are poorly un the First International Conference on Production derstood. Engineering, Design and Control, Alexandria, Egypt, December li80.

The final report which is now in preparation 1982 PUBLICATIONS AND REPORTS is based on preliminary.versions* delivered as seminars or invited papers. It is hoped that it Refereed Journals will stimulate additional research in the field of wear. 1. A. Misraand I. Finnie, "A Review of the Abrasive Wear of Metals," ASME J. Eng. Mat. Technol. _104, 94 (1982). b. Erosion-Corrosion Wear Program* Alan V. Levy, Investigator

1. MEASUREMENT AND NUMERICAL MODELING OF TWO 2. MEASUREMENTS OF AIR FLOW IN A CURVED PIPE PHASE FL0W+ USING LASER-DOPPLER VELOCIMETRY Joseph Humphrey, Farzad Pourahmadi, Michel Arnal, Maurice Holt, Jolen Flores, and Peter J. Turi and Alan Levy Before meaningful two-phase, gas-solid par The purpose of this research is to develop and ticle flow experiments can be conducted in the apply a numerical model that will predict the fluid mechanics test facility developed to study behavior of two phase flows composed of fluids erosive flows simulating conditions in coal cor with solid particulates in suspension. A model rosion equipment, single-phase, air-flow experi has been developed that is based on the continuum ments must be conducted. The computer driven hypothesis for both phases. It applies to both Laser Dopper Velocimetry (LDV) system was used to laminar and turbulent flows and has been used to study the flow of air near the entry section of a predict erosion in curved channels. 90* circular bend in a duct of 50 mm x 50 mm square cross section. Fiqure 1.1 shows predictions of erosive wear in a curved duct {3-D flow) predicted with the Data were collected in equally spaced-cross 2-D model. Agreement with measured erosion is planes in the bend, separated by angular inter good in regions of the flow where 3-D effects vals of 15°. Every data plane contained nine are weak. The 2-D limitation is among the re columns made up of 24 to 26 points each. With strictions being removed, as is the assumption in a given cross section, the probe volume was of a dilute particulate phase and fast particle brought within 2 mm of the wall for observation. response time. Curved channel-flow, erosive- Radial and axial velocity components were meas wear maps have also been predicted which permit ured in 10 planes normal to the curved duct wall. a relative evaluation of erosion through parti In each of these, velocity profiles were obtained cle impingement as a function of the flow Reynolds at nine stations spanning the duct, extending from number, particle response time, and bend angle of the vertical center plane to a parallel plane 1 mm the curved channel. The experimental results in from the wall. The stations were spaced at equal the literature that show large reductions in the distance of 6 mm. Vector velocity diagrams show turbulent kinetic energy of a turbulent two phase flow through viscous interaction effects were ing the evolution of the flow between entry and successfully predicted by the current model. the 90* station are displaced successive vertical planes. This information is the basis for the determination of the flow behavior of particles entrained in gases that simulate the erodent Brief version of LBL-13808. streans in coal conversion processes.

TBrief version of LBL-15659.

3. PARTICLE FLOW CHARACTERISTICS DETERMINATION IN GAS AND LIQUID-SOLID PARTICLE STREAMS'*"

Peter Turi, Jolen Flores, lonnis Kliafas, and Maurice Holt

The rates of erosion of metal and ceramic con tainment surfaces in energy conversion and utili zation systems are dependent upon the velocity, impingement angle, and solids loading of the car rier fluid. These variables are functions of the fluid mechanics in the various geometries of com ponents in the systems. In order to determine the nature of the fluid flow in two-phase sys tems, a complex text facility is required. Fig, 1.1. Predicted and experimental erosion rates. (XBL 824-2158) A Laser Doppler Velocimetry (LDV) system was

assembled toomake measurements on the flow of air through a 90° bend in a square duct. Measurements were facilitated through the use of a computer *This work was supported by the Director, Office controlled, X-Y-Z traversing table upon which the of Energy Research, Office of Basic Energy Sci laser optical components were fastened. Doppler ences, Materials Sciences Division of the U.S. signals wem received and processed by the LDV Department of Energy und> Contract No. frequency counter. These signals were then re DE-AC03-76SF00098. duced to mean velocities after undergoing a sta- 69

tistical analysis in a data acquisition software 2. M. Holt, J. Flores, and P. Turi, "Measurements package designed for this system. The system was of Air Flow in a Curved Pipe Using Laser-Doppler modified to overcome various problems determined Velocimetry," Proceedings of International Sym in its shakedown period. It will be utilized for posium on Applications of Laser Doppler Anemon- several years to study the behavior of 2 and 3 etry to Fluid Mechanics, Lisbon, Portugal, July phase fluid systems in various chemical process 5-7, 1982. system containment geometries. 3. P. Turi, "A Laser Dopper Velocimetry System • * * Designed for Two-Phase Flows," Pub-3027.

+Brief version of LBL-15660. LBL Reports 1. F. Pouramahdi, "Turbulence Modeling of Sin gle- and Two-Phase Curved Channel Flows," Ph.D. thesis, LBL-13808.

1982 PUBLICATIONS AND REPORTS 2. J. Humphrey, M. Chang, and M. Krodan, "De veloping Turbulent Flow in a 180" Bend and Down Refereed Journals Stream Tangent of Square Cross Sections," LBL-14844. 1. w. Yeung and M. Holt, "Boundary Layer Control in Pipes through Strong Injection," ZAMM 62, 391 Invited Talks (1982). ~~ 1. J. Humphrey, "Predicting Erosive Wear by Other Publications Solid Particles in Solid Gas/Solid Liquid Flows," Argonne National Laboratory, Argonne, Illinois, 1. J. Humphrey, F. Pouramahdi, and A. Levy, November 1982. "Prediction of Erosive Wear by Solid Particles in a Turbulent Curved Flow," Proceedings of 7th 2. J. Humphrey, "Curved Duct Turbulent Flow and Annual Conference on Coal Conversion and Utili Erosive wear by Solid Particulates," General zation, D0E-EPR1-BU, Gaithersburg, Maryland, Electric Company, Schenectady, New York, November November 1982. 1982. 70

c. Erosion of Brittle Solids* Anthony G. Evans, Investigator

Introduction. The intent of the program is to develop a fundamental comprehension of the erosion and erosion/corrosion of brittle surfaces, with emphasis on high temperature material removal. The study involves the observation and analysis of the impact damage and erosion mechanisms per tinent to homogeneous ceramics and glasses and to oxide films on metallic and ceramic alloys. The relatively comprehensive understanding of material removal by later:-! cracking—used to predict the dependence of the ?>• hiont temperature erosion of brittle materials on the fracture toughness, hard ness and elastic modulus—provides an established background for the study, /i.1 extension to the cracking along interfaces that occur?, in oxidative or corrosive environments is also being explored, as a basis for understanding erosion/corrosion problems.

Previous studies of surface damage in ceramics have identified a fracture threshold that dictates a transition from a modest to a rapid material removal rate. The dependence of this fracture threshold on material properties has yet to be adequately elucidated. Threshold studies consti tute a major theme of the current program.

1. THE MECHANICAL BEHAVIOR OF BRITTLE COATINGS AND LAYERS1" A. G. Evans, G, C. Crumley, and E. Demaray

The cracking and spelling of brittle coatings and layers on inorganic substrates have been evaluated. It is demonstrated that residually Fig. 1.1 Scanning electron micrographs of crack compressed coatings are susceptible to elastic propagation in oxide layers on NiCrAl superalloy. buckling in the presence of an interface separa (a) cracking through the AI2O3 and M)2 layers tion and that the buckled configuration yields a and (b) cracking it the Al203/superalloy interface stress intensification capable of crack growth because of void formation at the interface. and eventual spalling, A critical dimensionless (XBB 831-225) parameter far crack growth and spalling has thereby been identified. The parameter depends on the residual compression in the coating, the coatii.g thickness and the toughness of the inter face. Attempts have been made to compare the the A1203, alloy interface during oxygen exposure, predicted behavior with experimental observations is shown to appreciab'y reduce the interface of spalling, as required to interpret the effects toughness below that jf the ZrOp or AI2O3 (Fig. of temperature variation on the mechanical integ 1.1b), resulting in rremature spalling at this rity of the coatings and on their erosion resist interface during ei'ner temperature excursions or ance, both processes being dependent on brittle projectile impact. Void formation at the inter cracking ?nd spalling of the coating. The exper face and the efftctt. of rare earth additions are imental studies have been conducted on a NiCrAl presently being investigated, with special empha alloy coated with ZrO?. Mechanical studies have sis on the effects of residual stress at the in shown that the mechanical behavior of the system terface on void nucleation (cf creep cavitation). is limited by the properties of the Zr02 or AI2O3 layer in tht as-formed state, because cracks propagate preferentially through the ZrOg or AI2O3

*Ihis vfork was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under Contract No, 0E-ACO3-76SFOOO98. 71

2. MEASUREMENTS OF DYNAMIC HARDNESS BY A interpretation of their susceptibility to impact CONTROLLED IMPACT TECHNIQUE1" damage and erosion. 0. B. Marshall, A. G. Evans, and Z. Nisenholz

The magnitude of the impact induced residual "^Brief version of LBL-15339. stress field that governs crack initiation and growth under erosive conditions is strongly influenced by the dynamic hardness. A simple 1982 PUBLICATIONS AND REPORTS technique for measuring the dynamic hardness has been devised, based on the response to impact by LBL Reports a sapphire rod, with a pyramidal profile machined into the impact surface. The size of the hard 1. A. G. Evans, G. C. Crumley, and E. Demeray, ness impression has been related to the dynamic "The Mechanical Behavior of Brittle Coatings and hardness, through the impact velocity, the pro Layers," LBL-15474. jectile mass, etc. Application of this technique to ZnS has revealed that the hardness, for load 2. D. B. Marshall, A. G. Evans, and Z. Nisenholz, ing times in the range 1 to 10 ys, is more than "Measurement of Dynamic Hardness by a Controlled twice the static hardness. The increase in hard Impact Technique," LBL-15339. ness has been independently confirmed from Invited Talks measurements of the plastic zone size and of the residual depth of th^ surface impression. The higher hardness also accounts for the substantial 1. G. Crumley and A. G. Evans, "The Adherence of increase in crack size p ~

Conlacl Dimension, a/jun

Fig. 2.1. Hardness measurements and cracking induced by indentation, (a) optical micrographs compar'ng quasistatic and dynamic indentation damage and (b) the variation in indentation cracking for quasistatic and dynamic conditions, based on the rate induced change in hardness. (XBB 820-9210A) 72

d. Chemical Degradation of Refractories* David P. Whittle, investigator

Introduction. The energy technologies that the formation of a dense CaS layer approximately are most likely to be developed intensely in the 40 um thick at the specimen surface. In a recent next few decades relate to the use of coal; they ly published paper by Tak and Young,' it was re are coal combustion, liquefaction, and gasifica ported that calcium-aluminate-bonding phases are tion. In the reaction chambers of most of these prone to sulfur attack in Hg-HgS gas mixtures systems, ceramic materials are exposed to extreme (with an unknown oxygen potential) at temperatures ly aggressive environments. Temperatures up to up to 1,000'C. Recent experiment here confirms 1500 C, corrosive gases under high pressure, and this behavior (Fig. 1.1). It is proposed to try slag severely limit the materials that can be and establish the kinetic boundary on the thermo used. dynamic phase stability diagram and determine at what particular oxygen potential sulfur attack The objective of this program is to establish becomes a problem. the scientific principles of chemical interactions under conditions relevant to advanced coal tech nology systems. 'Brief version of LBL-15523. 1. J. B. Tak and D. J. Young, Ceramic Bulletin i. HIGH TEMPERATURE DEGRADATION OF REFRACTORIES 51, 7 (1982). IN MIXED GAS ENVIRONMENTS t Stephen Smith and David P. Whittle

To permit high temperature operation of coal technology systems, the reaction chamber must be refractory lined to insulate the external metal pressure vessel thermally, to protect it from chemical attack, and to minimize heat losses. Two systems of lining design are presently used. One is a layer of dense-alumina-castable refrac tory (caJcium-a)uminate-bonded alumina) at the hot face, with a layer of less dense, high alumi na castable between it and the pressure vessel wall. An alternative design uses dense alumina blocks, in which calcium oxide is present as a common impurity. The purpose of this work is to investigate the behavior rf the Al£03-Ca0 refrac tory system in gaseous atnospheres representative of those present in coal conversion systems.

Initially, it was proposed to study the behavior of pure A^^, pure CaO and AI2O3 up to 10/' CaO refractory specimens in H2-H2O-H2S gas mixtures of controlled oxygen, and sulfur fugaci- ties at 1200°C. The test environments used were very aggressive compared with actual coal conver sion atmospheres. Reference to the appropriate phase stability diagram indicates that CaO should be unstable and CaS would be expected to form,

Fo'lowing 250-hr exposure, pure AI2O3 and A1203 up to i0# CaO specimens were found not to be sus ceptible to sulfur attack. Pure CaO specimens were attacked by sulfur Fpecies and resulted in

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. +Dr. Whittle died in July 1982. This report has been prepared by Dr. Stephen Smith, Since Dr. Whittle's death, Dr. J. Stringer of the Electric Fig. 1.1. Scanning electron micrograph of AI2O3 - Power Research Institute has been acting as 10% CaO specimens, (a) Unexposed and (b) exposed technical advisor, pending the appointment of a to H2 - Z% H2S at 1200 C for 250 hr. full-trme successor. (XBB 831-995) 73 5. Experimental Research

a. Far Infrared Spectroscopy4

Paui L Richards, Investigator

Introduction. The objective of our research that occur in the cold environment. The sample is to use the infrared and near-millimeter is mounted in an ultrahigh vacuum system equipped wavelength range of the electromagnetic spectrum with surface preparation and characterization as a probe to do experiments that are selected facilities.' With this system, we can routinely for their technical novelty and potential for measure emission from as little as 0.05 L CO on revealing new physics. Ni, with a line center signal-to-noise ratio of 4 in one second of integration. We are developing new measurement techniques. including sensitive infrared detectors for use in We have observed thermally emitted infrared experiments in which the background photon level radiation from the carbon-oxygen stretching is low. The Ge:Ga photoconductors, the composite vibration of CO on a crystal of Ni that was cut bolometers, and the superconducting diode photon at about 8* from a (100) surface. The spectra of detectors developed by our group are now the most Ni with increasing amounts of CO on the surface sensitive existing infrared and near-mi llimei.:-** are shown in Fig. 1.1, normalized to room temper detectors over the wavelength range from 30 ym 10 ature blackbody emission. We observe two promi 8 mm. nent emission bands due to the C-0 stretching vibration. The strongest band, due to terminally We are now using sensitive infrared technology bonded molecules, falls in the range 2010-2035 to measure the spectra of one-dimensional conduc cm~l and has a width of about 35 curl. ^ weaker band from bridge-bonded molecules, with a width tors, of molecules chemisorbed on metal surfaces, 1 of dust clouds in our galaxy, and of the 3 K of 60-80 cnr , is observed in the range 1850-1930 cm-1. The peak frequencies shift continuously blackbody radiation that fills the universe.

1. INFRARED EMISSION SPECTROSCOPY OF CO ON Ni+ Shirley Chiang, Roger G. Tobin, and Paul L. Richards Vibrational spectroscopy yields valuable Jo.i % information about the structure and bonding of molecules to surfaces. We have developed the technique of infrared emission spectroscopy for use over the broad range of frequencies from 300 .' ' '"'•• 1.2 L to 3000 cm-1 (with a resolution of 1 to 15 cm"1) in order to permit the study of the linewidths of vibrational spectra of chemisorbed molecules. Conventional .eflection-absorption spectroscopy from highly reflective metal samples requires the tn ••-•••--. . • '-•'•. 0.9 L observation of the small surface absorption sig nal on top of the large background of the bulk reflection. Our infrared emission technique has i .-•-••-••..••.._..--•' •. the advantage that we observe the small surface emission signal on top of the much smaller back --'-•'""""" ' .'"• '-..•..0.6 L ground resulting from the bulk emission.

In order to observe the thermal radiation from •---'-•' """"' .-''. "- 0.4 L a room temperature, single-crystal sample, we cool the environment around the sample io -80 K s and cool our grating spectrometer to ~5 K. We -..-•-.•'""•'•"""""-•• —"' ''••-.-•.. 0.2 L obtain high sensitivity by using an extremely low noise Si:Sb photoconductive detector, which is .--,/.-••••'••'••--;-•••--••• ""' '""••'••-.••••- o.05 L limited by statistical fluctuations in the photon stream, even at the very low photon backgrounds 1800 1900 2000 2100 Frequency (cm-1) Fig. 1.1. Observed infrared emission spectra *This work was supported by the Director, Office from Ni(100)8° stepped surface as a function of of Energy Research, Office of Basic Energy frequency for CO exposures from 0.05 L to 1.2 L. Sciences* Materials Sciences Division of the U. S. The vertical bar indicated 0.1% absolute emissiv- [jRoartment of Energy under Contract No. ity. The instrumental resolution was 15 cnr*. 0E.'H^3-?6S?00D9B, (XBL 828-6354) 74

upward with increasing exposure, reaching a total field, and x-ray induced defect density to search shift of 25 cm-3- for the on-top site and 35 cm-1 for such an effect. for the bridge site at saturation- Development of this instrument is being continued And attempts At temperatures below 60 K, reflectance peaks are being made to observe the C-metel stretch have been observed at 7 and 29 curl (Fig. 3.1). absorption. The 29 cnr* peak is very sensitive to radiation- induced defects and is insensitive to magnetic fields up to 40 kS at 4.4 K. In contrast to re ports by others, our results suggest that these •^Brief version oV LBL-14552 features are not related to a superconductive pseudogap.

2. LOW TEMPERATURE INFRARED ABSORPTION SPECTROSCOPY OF CO ON Ni + tIBM Research Laboratories, San Jose, CA. Harry J. Levinson,* Roger G. Tobin, and Paul L. Richards

1 1 i l | 1 1 1 1 1 !•!•:•! I- i i i i i i i i | i i i i The infrared absorption spectrometer developed in our group is a sensitive probe of the vibra tional structure of molecules adsorbed on metal films at low temperatures. A sensitive thermom 60K/80K eter measures the sample temperature change, as infrared radiation from a rapid-scan Fourier spectrometer is absorbed. The sample is in 40K/60K ultrahigh vacuum. It is held at 1.5 K during the measurements, but it can be heated to -50 K to study temperature-dependent effects. This low —^30H/60K temperature regime is of particular interest for studies of chemisorption kinetics and molecular surface diffusion. /^^EOK/eOK

We have investigated in detail the adsorption of CO on evaporated nickel films at 1.5 K and at /\. 2K/BDK 40 K, as a function of surface coverage. In contrast to published reports, we have found no T evidence for a physisorbed precursor state. Sub 10% stantial surface diffusion occurs when the sample _L ...... i ... . is heated to 40 K, but some regions are apparent t ly unaffected. In addition, we observed an un 1 explained splitting of the infrared band due to Wavenumber (cm* ) molecules bonded to a single nickel atom, at high Fig. 3.1. Reflectance of (THTSFjg CIO4 as a CO coverages. function of temperature. (X3L 831-5046)

'Brief version of LBL-14556. 4. WORK IN PROGRESS ^Advanced Micro Devices, Sunnyvale, CA. Studies of hole transport in Ge:Ga are being pursued to understand the semiconductor physics 3. FAR INFRARED OPTICAL PROPERTIES OF AN ORGANIC that underlies the performance of technologically SUPERCONDUCTOR important far infrared detectors. Current-voltage curves and the Hall effect are being measured as William A. Challener, Paul L. Richards, and a function of temperature, photon flux, and elec Richard L. Greene"*" tric field. Many important detector properties depend on the sensitivity of the hole lifetime to The charge transfer compound (TMTSF)2 CIO4 these parameters. Detectors have been produced is the first organic compound to be synthesized with noise performance at very low photon back that becomes superconducting at ambient pressure. grounds equal to the (BLIP) limit set by the fluc The nature of the highly conducting state above tuations in the arrival of background photon*.

Tc -= 1 K is a matter of controversy. One hypoth esis suggests that quasi-one-dimensional super The far infrared properties of the quasi-one- conducting fluctuations exist in this material up dimensional charge density wave (CDW) compound, to 40 K. If this is true, a pseudogap of about NbSe3, are bding measured. Reflectivity data 3.8 MeV or 30 cnr* should exist in the electronic show a plasma edge, phonon modes made infrared density of states that might produce an observ active by the CDW transition, and a possible COW able feature in the far infrared optical proper energy gap. ties of this material. We have made both reflectance and transmittance measurements from 5 A new experiment is being prepared to measure to 40 cm-1 as a function of temperature, magnetic the spectrum of the cosmic microwave background 75

radiation. It will be different in most respects +6. A. D. Smith, W. R. KcGrath, P. L. Richards, from our previous experiment. It is designed to D. E. Prober, and P. Santhan an, "SIS Quasiparticie test the apparent deviations from a blackbody Tunnel Junctions as Microwave Mixers and Direct spectrum. Detectors," Bull. A*. Phys. Soc. 27, 266 (1982).

A balloon experiment designed to survey the +7. W. R. McGrath, A. D. Smith, P. L. Richards, sky for far infrared sources was successfully R. E. Harris, and F. L. Lloyd, "Noise Measure flown in 1982. Data were obtained over 2/3 of ments in SIS Quasiparticie Array Mixers," Bull. the northern sky at seven wavelengths between Am. Phys. Soc. 27, 266 (1932). 20 ym and 2 mm. A preliminary catalog is being prepared of hundreds of far infrared sources, many of which were not previously known. LBL Reports

Calculations are being carried out to see if 1. S. Chiang, R. G. Tobin, and P. L. Richards, synchrotron radiation is a useful source for "Infrared Emission Spectroscopy of Co on Ni," to infrared spectroscopy. When diffraction effects be published in a special issue of J. of Electron are included, it appears that the time average Spectroscopy and Related Phenomena, LBL-14552. brilliance of a source such as the proposed Advanced Light Source will be very useful for 2. H. J. Levinson, R. G* Tobin, and P. L. wavelengths longer than 10 n. Fast pulses will Richards, "Infrared Spectra of CO Adsorbed at Low be useful for measurements of relaxation times. Temperatures on Hi," to be published in a special issue of the Journal of Electron Spectroscopy and Related Phenomena, LBL-14556. 1982 PUBLICATIONS AND REPORTS 3. M. R. Hueschen, E. E. Haller, and P. L. Refereed Journals Richards, "Ge:Ga Photoconductors: Development and Ideal Performance," to be published in the tl. A. D. Smith and P. L. Richards, "Analytic Proceedings of the Seventh International Con ference on I-R and mm Waves, LBL-14998. Solutions to SIS Quantum Mixer Theory," J. Appl. Phys. 53(5), 3806 (1982). 4. W. A. Challener, P. L. Richards, and R. L. 2. P. L. Richards, "Spectrum of the Microwave Greene, "Far Infrared Optical Properties of Background Radiation," Phil. Trans. R. Soc. Lond. TMTSFj CIO4," to be published in the Proceed A 307, 77 (1982); LBL-14311. ings rf the International Conference on Low Dimensional Conductors and Superconductors, LBL-15279. 3. W. R. McGrath and P. L. Richards, "A Con venient Low Temperature Heat Sink for Electrical Leads," Rev. Sci. Instrum. 53(5), 709 (1982); 5. P. L. Richards, "Infrared Measurements of LBL-13764. Molecules Chemisorbed on Metal Surfaces." to be published in the proceedings of the Symposium on +4. P. L. Richards, "Superconducting Microwave Photoprocesses on Solid Surfaces, LBL-15337. Devices Reach Fundamental Quantum Limits," Phys. 81 38, 215 (1982). 6. S. Chiang, R. G. Tobin, and P. L. Richards, "Infrared Emission Spectroscopy of CO on Ni(100)," Other Publications to be published in the Bull. Am. Phys. Soc., LBL-15379. 1. M. R. Hueschen, E. E. Haller, and P. L. Richards, "Lifetime and Mobility in Ge:Ga Far 7. W. A. Challener, P. L. Richards, and R. L. Infrared Photoconductors," Bull. Am. Phys. Soc. Greene, "Far Infrared Optical Properties of 27. 391 (1982); LBL-13761. (TMTSF)g ClO^," to be published in the Bull. Am. Phys. Soc., LBL-15380. 2. W. A. Challener and P. L. Richards, "Far Infrared Optical Properties of NbSe3," Bull. *8. J. L. Bonomo, J. B. Peterson, P. L. Am. Phys. Soc. £7, 283 (1982); L8L-13762. Richards, and T. Timusk, "Calibration of a Photo meter for Measurement of the Cosmic Microwave 3. S. Chiang, R. G. Tobin, and P. L. Richards, Background," to be published in the Proc. of the "Infrared Emission Spectroscopy from Surfaces," International School of Physics, "Enrico Fermi," Bull. Am. Phys. Soc. 2Z, 345 (1982); LBL-13763. Vol. LXXXVI, LBL-14739.

+4. P. L. Richards and L. T. Greenberg, "Infra red Detectors fow Low-Background Astronomy: Invited Talks by P. L. Richards Incoherent and Coherent Devices from One Micro meter to One Millimeter," Infrared and Millimeter Talk I, "Infrared Measurements of the Spectrum of Waves, Vol. 6, edited by Kenneth J. Button, the Cosmic Blacfcijody Radiation," given at: Academic Press, 1982, p. 149-207. 1. Physics Colloquium, University of Regensburg, +5. P. L. Richards, "Superconducting Detectors W. Germany, February 8, 1982. and Mixers for Near-Millimeter Wavelengths," McGraw Hill Yearbook of Science and Technology 2. Seminar, Cambridge University, England, March 1982-1983, p. 438-439: 9, 1982. 76

3. Seminar, Rheinisch-Westfalische Technische 7. Seminar, Observatoire de Paris, Meudon, Hochschule Aachen, W. Germany, May 6, 1982. France, May 14, 1982.

4. Seminar, Phsikalisches Institut University of 8. Solid State Colloquim, Cambridge University, Tubingen, W. Germany, May 19, 1982. England, May 26, 1982.

5. Seminar, Istituto di Fisica Superiore, 9. Seminar, Max Planck Institut fur Universita di Firenze, and CNR-Istituto di Ricera FestkBrperforschung, Stuttgart, W. Germany, June sulle Onde Elettromagnetiche, Florence, Italy, 9. 1982. May 31, 1982. 10. Seminar, Laboratoire Infrarouge Lointain, 6. Phvsics Colloquium, University of St. Andrews, University de Nancy 1, France, June 18, 1982. Scotland, May 28, 1982. 11. Seminar, Academy of Sciences, Space Research 7. Seminar, E.T.H., Zurich Switzerland, June 10, Institute, Moscow, U.S.S.R., June 30, 1982. 1982. 12. Solid State Colloquium, University of 8. Colloquim, Max Planck Institut fur Hamburg, Hamburg, U. Germany, July 8, 1982. FestkbVperforschung, Stuttgart, West Germany, June 15, 1982. 13. Lecture, International School of Physics "Enrico Fermi," Varenna, Italy, July 19, 1982. 9. Seminar, Laboratoire Inirarouge Lointain, Universlte de Nancy, France, June 18, 1982. Talk III, "Detectors of Far Infrared and mm 10. Colloquium, Max Planck Institut fur Physik Waves," given at: und Astrophysik, Garching, West Germany, June 25, 1982. 1. Seminar, Istituto di Fisica Superiore, Universita di Firenze and CNR-Istituto di Ricerca 11. Seminar, Academy of Sciences, Space Research sulle Onde Electromagnetiche, Florence, Italy, Institute, Moscow, U.S.S.R., June 30, 1982. June 1, 1982.

12. General Colloquium, Technical University of 2. Seminar, Academy of Sciences, Space Research Munich, Garching, W. Germany, July 5, 1982. Institute, Moscow, U.S.5.R., June 30, 1982. 13. Lecture, International School of Physics "Enrico Fermi," Varenna, Italy, July 16 and 18, Talk IV, "Spectrum of the Microwave Background 1982. Radiation," given at:

1. Royal Society Discussion Meeting. The Big Talk II, "Superconducting Microwave Oevices Reach Bang and Element Creation, London, England, Fundamental Quantum Limits," given at: March 11, 1982.

1. Low Temperature Seminar, Oxf •-'d University, 2. U.C. Santa Barbara, Theoretical Physics England, March 4, 1982. Institute, Colloquium, September 22, 1982.

2. Seminar Queen Mary College, University of 3. XI Texas Symposium on Relativistic Astro London, England, March 5, 1982. physics, Austin, Texas,, December 12-16, 1982. 3. Seminar Max Planck Institut fur Radio- astronomie, Bonn, w. Germany, February 4, 1982. Talk V, "Progress in Far Infrared Bolometer Research," given at: 4. Plenary Talk, German Physical Society, [•funster, W. Germany, March 31, 1982. 1. Workshop on the Scientific Importance of Submi11imeter Observations, E.S.A., Noordwijk, 5. Seminar, Bell Laboratories, Murray Hill, New The Netherlands, May 10-12, 1982. Jersey, April 20, 1982.

6. Seminar, Physikalisches Institut, University ^Supported also by the Office of Naval Research. of Stuttgart, U. Germany, May 4, 1982. ^Supported also by NASA. 77

b. Experimental Solid State Physics and Quantum Electronics*

Yuen-Ron $hen, Investigator

1. SPECTROSCOPY OF MOLECULAR MONOLAYERS BY- RESONANT SECOND-HARMONIC GENERATION"1" O Rhodamin« 1(0 Tony F. Heinz, Chenson K. Chen, Daniel Ricard, and Y. Ron Shen • Rhodomine 6 G

Second-order nonlinear optical processes are forbidden in media with inversion symmetry. The surface atomic or molecular layers, on the other hand, are always asymmetric, and their contribu tion to the second-order processes can often dominate over that of the bulk. Therefore, second-order nonlinear optical effects from the surface can be used as sensitive probes for sur face studies. That the nonlinear optical tech nique has indeed the sensitivity to detect a submonolayer of adsorbed molecules has been demonstrated in our earlier investigations.

To show that the nonlinear optical technique can actually be applied to surface studies, an experiment has recently been carried out in our laboratory using surface second-harmonic (SH) generation to study a submonolayer of dye mole cules adsorbed on a fused quartz substrate. Sam ples of rhodamine 110 and rhodamine 6G with an average surface coverage of 5 x lO1^ molecules/cm2 were prepared by the spinning technique. A dye laser pumped by a Q-switched Nd3+-doped yttrium aluminum garnet laser provided tunable pulses approximately 10 ns duration, 1 cur* linewidth, 320 340 360 and 1 mj energy. The output of the dye laser, SH Wavelength (nm) focused to an area of 10-3 cm^, fell on the sam ple at an angle of 45*. The reflected SH light, Fig. 1.1. Normalized SH intensity for p-polarized which amounted to ~104 photons per pulse for the excitation of monolayer samples of rhodamine 110 peak signal, was detected by a photomultiplier and and rhodamine 6G on fused silica as a function of a gated integrator after it passed through low the SH wavelength in the region of the S0 > S2 frequency blocking filters and a monochromator. transition. (XBL 8110-6773)

Figure 1.1 displays the observed SH spectra for the monolayer samples in the region of tlv ization dependence of the SH output suggests a

SQ » S£ electronic transits . The resonant SHG molecular orientation in which the y'-axis of the process is described in Fig. 1.2, which also molecule (see Fig. 1.2) is in the surface plane, shows the transition energies of the relevant and the z'-axis is tilted 34* from the surf 1.-3 states for the two dyes. normal.

The SH signal was found to be independent of the rotation of the sample about its surface nor mal, indicating a fully isotropic distribution of +Br1ef version of Phys. Rev. Lett. 48, 478 the molecules in the surface plane. The polar- (1982); LBL-13667. ""

S 30,000 cm'1 2 28,800 cm"'

19,600 cnf[- • 18,900 cm"1

HjC>5^Y^kCH3 i^,C02C2H f uC02H 5 I—»-x' I—,x<

s0v

Rhodamine 110 Rhodamjne 6G

Fig. 1.2. Energy-level diagrams for rhodamine 110 and rhodatnine 6G with the line centers for the linear absorption of the dyes dissolved in ethanol given in units of inverse centimeters. The structure of the dyes and the molecular axes referred to in the text are indicated. (XBL 8111-12843)

2. TRANSIENT FOUR-WAVE MIXING AND COHERENT time sequence and separation of the input pulses. TRANSIENT OPTICAL PHENOMENA* By choosing the input frequencies to excite the medium resonantly or near-resonantly, coherent Peixian Ye and Y. Ron Shen superpositions of states and populations can be created. Thus, experiments on transient four- Four-wave mixing has recently become one of wave mixing can be used not only to study the the most interesting and thoroughly investigated particular time-ordered four-wave mixing process nonlinear optical effects. It is a process that itself, but also to obtain the various relaxation is allowed in all media, and has therefore found rates in the medium. numerous important applications. The inherent resonant enhancement feature allows the process Transient four-wave mixing can be considered to be exploited as a new spectroscopic technique. as a special class of phenomena amoiig all of the For example, witi« tb* appropriate experimental possible coherent transient optical effects. In arrangement, four-wa-e mixing can be used to ob cluded in this class are the various known cases tain Doppler-free spectra or spectra with reduced of photon echoes, such as trilevel echoes, stimu inhomogeneous broadening, to study transitions lated echoes, and backward echoes. Although between excited states, to measure longitudinal these echo phenomena are usually discussed in and transverse relaxation times, etc. The terms of the vector model of excitation in i non- systematic study of four-wave mixing has so far perturbative approach, in the limit in which no been restricted to the steady-state case. With pump saturation occurs, they can be treated as time as an additional variable, transient four- transient four-wave mixing processes. On the wave mixing offers more possibilities. other hand, transient four-wave mixing is more general and predicts coherent transient effects A general formalism has been developed by us other than the photon-echos phenomena. It to describe transient four-wave mixing. The covers, for example, the cases of free-induction results of such processes

3. NONLINEAR WAVE INTERACTION INVOLVING SURFACE microscopic ones, we can describe directly the POLARITONS* amplification of the incident and radiated field induced by the presence of the surface. The Y. Ron Shen and Francesco DeMartini surface enhancement of any particular process can then be readily calculated. Nonlinear optical studies involving surface polaritons have attracted increasing attention On the experimental side, while both recently. Because the surface polaritons are surface-enhanced Raman scattering the SHG have localized to a thin surface layer near an inter been observed, they have not been simultaneously face, nonlinear optical effects involving surface measured and correlated with the different phases polaritons have a surface-specific nature. In of oxidation-reduction cycles in an electrochemi fact, surface nonlinear optics with all of the cal cell. The Raman and second-harmonic signals interacting waves being surface polaritons are from a silver electrode were monitored during also possible. With tunable laser excitation, cycling in pure electrolytes (K2SO4 or KC1) and new techniques of surface nonlinear optical during cycling with cyanide ions also present. spectroscopy can be devised and applications to In the latter case, a rich surface chemistry surface science can be envisioned. resulted. The rather different responses of the two optical probes could be interpreted with the We have developed a general formalism to aid of voltammograms indicating the onset of describe the surface polaritons. It is shown various reactions. Using a simple geometric that surface polaritons can exist in a multilayer model, predictions are made of the macroscopic system. The theory of linear excitation of sur local-field enhancements for SHG and Raman scat face polaritons is given. It is then extended to tering. Experimental values for both processes the case of nonlinear optical excitation with the with identical excitation of a given sample can nonlinear polarization acting as the driving then be compared. For the chosen pump radiation, source. The interaction of surface polaritons the second-harmonic nonlinearity proves to be with bulk waves and the interaction between sur dominated by that of the silver itself. For this face polaritons are treated from a unified point case, the macroscopic local-field corrections of view. The generation of surface polaritons by should completely account for the surface enhance optical mixing of bulk waves can be considered as ment. From the experimental Raman scattering a special case of nonlinear optical reflection power, we can then estimate the residual enhance from a surface. The same formalism can be used ment of the Raman cross section associated with to describe the generation of bulk and surface microscopic local fields and the direct molecule- waves by optical mixing of surface polaritons or metal interaction. surface polaritons with bulk waves.

TBrief version of LBL-14840. TBrief version of LBL-11358.

4. SURFACE-ENHANCED SECOND-HARMONIC GENERATION AND RAMAN SCATTERING 1982 PUBLICATIONS AND REPORTS

Chenson K. Chen, Tony F. Heinz, Daniel Ricard, Refereed Journals and Y. Ron Shen 1. H. W. K. Tom, C. K. Chen, A. R. B. de Castro, The phenomenon of surface-enhanced Raman and Y. R. Shen, "Effect of Extended Surface scattering has attracted and continues to attract Plasmons on Surface Enhanced Rai?an Scattering," considerable attention. An appreciable enhance Solid State Commun. 4^, 259 (1982); LBL-13027. ment in the effective Raman scattering cross section has been manifested by a wide range of 2. Peixian Ye and Y. R. Shen, "Transient molecular adsorbates on surfaces of various metals Four-Wave Mixing and Coherent Transient Optical at solid/liquid, solid/vacuum, and even at solid/ Phenomena," Phys. Rev. A. 25, 2183 (1982); solid interfaces. It has come to be accepted that LBL-13462. the macroscopic electrodynamics of the surface plays a significant role in SERS: the presence t3. S. D. Durbin, S. M. Arakelian, and Y. R. of the roughened metal can produce a local field Shen, "Strong Optical Diffraction in a Nematic strength at the interface which greatly exceeds Liquid Crystal with High Nonlinearity," Optics that of the applied field. This mechanism of Lett. 7_> 145 (1982). local field enhancement should affect all surface optical processes. The second harmonic genera tion (SHG) process is of particular interest 4. T. F. Heinz, C. K, Chan, 0. Ricard, and Y. R. since it is forbidden in the bulk of a centro- Shen, "Spectroscopy of Molecular Monolayers by symmetric medium, and has, consequently, an Resonant Second-Harmonic Generation," Phys. Rev. intrinsic surface sensitivity. Lett. 48, 478 (1982); LBL-13667. 5. M. F. Vernon, D. J. Krajnovich, H. S. Kwok, We h&ve elaborated the theory of local-field J. M. Lisy, Y. R. Shen, and Y. T. Lee, "Infrared enhancement in a general fashion. By extending Vibrational Predissociation Spectroscopy of Water the notion of a correction to the molecular Clusters by the Crossed-Molecular Beam Technique," polarizability from macroscopic local fields to 0. Chem. Phys. 77, 47 (1982). 80

6. R. Hsu and Y. R. Shen, "Effects of 7. C. K. Chen, T. F. Heinz, D. Ricard, and Y. R. Self-Induced Ellipse Rotation and Self-Focusing Shen, "Nonlinear Optical Study of Interfaces," in a Q-Switched Laser Cavity," Appl. Optics 21, Proceedings of the International Conference on 2608 (1982). ~~ Lasers '81. New Orleans, Dec. 14-18, 1981, STS Press, McLean, VA, 1982, p. 61; LBL-13878. LBL Reports 8. Y. R. Shen, "Recent Advances in Optical 1. A. Jacobson, "Coherent Rayleigh-Brillouin Bistability," Nature 299. 779 (1982); LBL-14971. Spectroscopy," Ph. D. thesis, LBL-14373. 9. Y. R. Shen and F. DeMartini, "Nonlinear Wave 2. D. Krajnovich, F. Huisken, Z. Zhang, Y. R. Interaction Involving Surface Polaritons," in Shen, and Y. T. Lee, "Competition Between Atomic Surface Polaritons, edited by V. M. Agranovitch and Molecular Chlorine Elimination in the and D. L. Mills, North Holland, NY, 1982, p. 629; Infrared Multiphoton Dissociation of Cf2Cl2," LBL-11358. LBL-14478. 10. S. D. Durbin, S. M. Arakeliap, M. M. Cheung, 3. C. K. Chen, T. F. Heinz, D. Ricard, and Y. R. and Y. R. Shen, "Nonlinear Optical Effects in a Shen, "Surface-Enhanced Second-Harmonic Genera Nematic Liquid Crystal Resulting from Laser- tion and Raman Scattering," LBL-14840. Induced Refractive Indices," Appl. Phys. B 28, 145 (1982). ~ 4. T. F. Heinz, "Nonlinear Optics of Surfaces and Adsorbates," Ph. D. thesis, LBL-15255. 11. T. F. Heinz, C. K. Chen, D. Ricard, and Y. R. Shen, "Nonlinear Optical Detection of Adsorbed 5- R. Hsu, "Nonlinear Effects of Materials in Monolayers and Monolayers Spectroscopy," Aopl. Laser Cavities," Dh. D. thesis, LBL-11519. Phys. B 28, 229 (1982); LEL-13829 Abs.

6. M. F. Vernon, J. M. Lisy, D. J. Krajnovich, Invited Talks A. Tramer, H. S. Kwok, Y. R. Shen, and Y. T. Lee, "Vibrational Predissociation Spectra and Dynamics 1. J. M. Lisy, M. F. Vernon, H. S. Kwok, of Small Molecular Clusters of H?0 and HF," A. Tramer, D. J. Krajnovich, Y. R. Shen, and LBL-13740. Y. T. Lee, "Vibrational Predissociation Dynamics and Spectroscopy of Small Molecular Clusters," Other Publications Faraday Discussion #73, Van der Waals Molecules, St. Catherine's College, Oxford, England, April 1. D. Krajnovich, Z. Zhang, F. Huisken, Y. R. 5-7, 1982. Shen, and Y. T. Lee, "The Effects of Reagent Translational and Vibrational Energy on the 2. M. F. Vernon, J. M. Lis v. D. J. Krajnovich, Dynamics of Endothermic Reactions," in Physics of A. Tramer, H. S. Kwok, Y. R. Shen, and Y. T. Lee, Electronic and Atumic Collisions, edited by "Vibrational Predissociation Spectra and Dynamics 5. Datz, North Holland, NY, 1982, p. 733; of Small Molecular Clusters of HjO and HF," LBL-12982. Faraday Discussion #73, Van der Waals Molecules, St. Catherine's College, Oxford, England, Ap-ii 2. Y. R. Shen, "Nonlinear Optical Techniques for 5-7, 1982. Surface Studies," in Novel Materials and Tech niques in Condensed Matter, edited by G. W. 3. T. F. Heinz, C. K. Chen, D. Ricard, and Y. R. urabtree and P. Vashishta, North Holland, NY, Shen, "Nonlinear Optical Detection of Adsorbed 198?, p. 193; LBL-13365. Monolayers and Monolayer Spectroscopy," XII International Quantum Electronics Conference, 3. T. F. Heinz, C. K. Chen, D. Ricard, and Y. R. Munich, W. Germany, June 22-23, 1982. Shen, "Optical Second-Harmonic Spectroscopy of Molecular Monolayers," Bull. Am. Phys. Soc. 27, f4. S. D. Durbin, S. M. Arakelian, M. M. Cheung, 77 (1982); LBL-13715 Abs. and Y. R. Shen, "Nonlinear Optical Effects in a Nematic Liquid Crystal Resulting from Laser- +4. S. D. Durbin, M-M. Cheung, S. M. Arakelian, Induced Refractive Indices," XII International and Y. R. Shen, "Quantitative Studies of Some Quantum Electronics Conference, Munich, W. Highly Nonlinear Optical Effects in Nematic Germany, June 22-23, 1982. Liquid Crystals," Bull. Am. Phys. Soc. 27, 328 (1982). — +5. S. D. Durbin, S. M. Arakelian, M. M. Cheung, and Y. R. Shen, "Highly Nonlinear Optical Effects 5. C. K. Chen, T. F. Heinz, D. Ricard, and Y. R. in Liquid Crystals," International Workshop on Shen, "Correlation of Surface Enhanced Second Optical Phase Conjugation and Instabilities, Harmonic Generation and Raman Scattering of Cargese, Corsica. September 20-24, 1982. Molecules Adsorbed to a Silver Surface," Bull. Am. Phys. Soc. 27, 377 (1982), LBL-13717 Abs. f6. S. D. Di'rbin, Y. R. Shen, and S. M. Arakelian, "Strong Dynamical Self-Diffraction 6. G. T. Boyd, Z. H. Yu, and Y. R. Shen, Effects in a Nematic Liquid Crystal: Experi "Multiphoton-Induced Luminescence from Roughened mental Investigation," XI National Conference on Metal Surfaces," Bull. Am. Phys. Soc. 27, 377 Coherent and Nonlinear Optics, Yerevan, USSR, (1982), LBL-13718 Abs. November 22-25, 1982. 81

7. Y. R. Shen, "Nonlinear Optical Studies of 13. Y. R. Shen, "Lasers and Surface Science," Adsorbed Monolayers," Optical Society Meeting, seminar at Ecole Polytechnique, Palaiseau, Tuscon, Arizona, October 18, 1982. France, September 12-18, 1982.

8. Y. R. Shen, "Surface Nonlinear Optics," U. C. 14. Y. R. Shen, "Nonlinear Optical Effects in Davis, Colloquium, November 9, 1982. Liquid Crystals," seminar at Ecole Polytechnique, Palaiseau, france, September 12-18, 1982. +9. Y. R. Shen, "Highly Nonlinear Optical Effects in Liquid Crystals," Quantum Electronics Seminar, 15. Y. R. Shen, "Lasers and Surface Science," Stanford University, November 22, 1982. Technische l/niversitat, Wien, Austria, June 21, 1982. 10. Y. R. Shen, "Recent Advances in Nonlinear Optics," Lawrence Liverraore Laboratory Col'oquium, 16. Y. R. Shen, "Study of Molecular Adsorption at November 23, 1982. an Interface," Oak Ridge National Laboratory, Oak Ridge, Tennessee, May 5-7, 1982. 11. Y. R. Shen, "Applications of Nonlinear Optics to Surface Studies," Toronto University Colloqui 17. Y. R. Shen, "Surface Studies by Nonlinear um, December 7, 1982. Optical Techniques," Lockheed Missiles and Space Co., Inc., Palo Alto, California, May 13, 1982. 12. Y. R. Shen, "Applications of Nonlinear Optics to Material Studies," Condensed Matter Physics * * * Meeting, Beijing, China, December 28, 1982- ^Research supported by the National Science January 3, 1983. Foundation under Grant DMR81-17366. c. Excitations In Solids* Carson D, Jeffries, Investigator

Introduction. There exists a large class of nonlinear dissipative systems with very complex behavior. One is faced with the problem of form ulating and, if possible, answering new types of questions which are independent of detailed knowl edge of system dynamics. This is what is done in the renormalization group formulation of critical phenomena; the questions and answers become uni versal in a certain sense. An analogous universal viewpoint has recently been developed for dealing with systems which display recognizable patterns as they are driven harder, to points of instabil ity and onset of a pseudorandom or so-called cha otic state. Examples are: onset of turbulence in fluids; noisy electrical, mechanical, and chem ical oscillators; and "solid state turbulence," such as plasma instabilities in semiconductors, 4.0 spin wave instabilities, acoustic and electro- acoustic instabilities, and piezo and ferroelec Fig. 1.1. Computed values of the dynamical vari tric instabilities. Many of these systems display able x vs the driving parameter x for the quad qualitatively similar routes to chaos. The goal ratic logistic difference equation. of this research ib a detailed experimental study (XBL 823-8500) of solid state turbulence and an analysis based on present theoretical models of the dynamical structure of chaotic behavior. This has applica Fig. 1.2 was obtained, in surprisingly good agree tions to materials and processes of technological ment with theory,Fig. 1.1: bifurcation, onset of importance. chaos, band merging, and periodic windows are all observed.

More detailed measurements on power spectra and 1. PERIOD P/'JBLING AND UNIVERSAL CHAOTIC BEHAVIOR effects of additive noise provide a direct compar IN P-N JUNCTIONS IN SILICON* ison between measured and theoretical values for five universal numbers in Table 1.1. Carson Jeffries, Jose Perez, and James Testa A period doubling route to chaos has been pro posed by Feigenbaum and others. This route may be approximately modeled by a simple recursion relation, or map, such as the logistic equation

xn+i = xxn(l-xn), where x is the driving parame ter. The bifurcation diagram, Fig. 1.1, plots the

iterated value {xn }vs x. As x is increased, {xn} displays a sequence of pitchfork bifurcations at n xn, with period doubling by 2 , converging geomet

rically like (xc - xn) « «-", to the onset of chaos

at \c, where {xn} becomes aperiodic. In the chaotic regime, noise bands merge and narrow per iodic windows emerge in a specific order and pat tern. This model is made quantitative by com puted values of some universal numbers (as n > <*): convergence rate s, pitchfork ratio a, power spec tral ratio R, wide band noise scaling factor 0, and noise sensitivity factor K.

To make a quantitative test of the model, data were taken on a p-n silicon junction driven res Fig. 1.2. Measured values of the peak current I onantly by a sinusoidal voltage V0(t). By sampl (vertical) vs the driving voltage V0 for a p-n ing and displaying the successive peak values of junction. This bifurcation diagram shows the the diode current I, the bifurcation diaqram of features of the model, Fig. 1.1. (XBB 828-7406)

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the (J. S. Department of Energy under Contract No. DE-AC03-76SF00098. Table 1.1 Comparison—Theory and Experiment.

Universal Number Measured Value

Bifurcation ratio 6 = 4.669a 4.26 * 0.5

Pitchfork ratio a = 2.5023 2.43 * 0.1

Power spectral ratio R = 13.2 dbD 13 ± 2 db

Noise sensitivity factor 8 = 6.619 c 6.5 * 0.5

Wide band noise 6 = 3.237°" 3.26 ± 0.4

aFeigenbaum. DNauenberg and Rudnick. cCrutchfie1d, Nauenberg, and Rudnick. dHuberman and Zisook.

These are the most detailed measurements to be re for very small values of e where some significant ported for a real physical system; they strongly deviation is found. Possible causes are being suggest a universal period doubling route for the examined. p-n junction under the operating conditions used. For other operating conditions, e.g., a much larg er driving voltage, more complex behavior is ob served, characteristic of a higher dimensional fBrief version of Phys. Rev. A 26, 2117 (1982). map.

3. PERIOD DOUBLING AND CHAOS IN SPIN WAVE INSTABILITIES IN YTTRIUM IRON GARNETt tBrief version of Phys, Rev. Lett. 48, 714 (1982) and Phys. Rev. B jtf, 3460 (1982). George Gibson and Carson Jeffries

It has been known previously that ferromagnet 2. INTERMITTENCY ROUTE TO CHAOS ic resonance in a sphere displays the so-called Suhl instability because of coupling of the Carson Jeffries and Jose Perez uniform precession mode with spin wave modes. Although Suhl writes "...the situation bears a Another route to chaos has been proposed by certain resemblance to the turbulent state in Manneville and Pomeau, which is characterized by fluid dynamics...," the behavior was not fully a periodic (laminar) phase randomly interrupted understood. by bursts of aperiodic behavior. This occurs near a tangent bifurcation, e.g., near the period A reexamination of this phenomenon has been 3 window in Fig. 1.1 of the preceding article as done for YIG spheres at f = 1.2 GHz. Autooscil- the driving parameter x is reduced by a small lations at 16 kHz were observed corresponding to amount e from the threshold-value for the peri standing spin wave modes. As the rf driving field odic window. Theory predicts that the average was increased, we observed threshold values for -0,5 laminar length <%> « e . In the window it period doubling, onset of chaosy intermittency, self intermittency may be induced by adding a periodic windows, and hysteresis. The behavior random noise voltage of standard deviation g; the is considerably more complex than found in p-n predicted scaling behavior is « g-0.G66. jhe junctions but less complex than found in fluids. probability distribution P(fc) is also predicted. It is clear that one or more distinct routes to chaos are being followed. For some cases the Poincare* return map has a close resemblance to Using the same driven p-n junction as in the that predicted from the two-dimensional quadratic preceding article, we observe the intermittency Henon map in the limit where the map is nearly in the threshold of the period 5 window. Using area preserving. This corresponds to a system real-time analysis of the diode voltage with win which has relatively low loss, which would be the dow comparators and additional logic circuitry to case for a weak coupling of the spin waves with detect the beginning and ending of a laminar train the crystal lattice. allowed a quantitative measurement of the average length . The data yielvield <* E-(0.45±0.005J and a g-•(0.65*0.005)1 . This is an interesting system, again dis playing aspects of universal chaotic behavior, This is the first experiment to quantitatively somewhat like a "rpin-liquid" but with very low measure the scaling uehavior of , and it is viscosity. Further studies of magnetic instabil found to be in agreement with expectations except ities are under way. conductor Oscillator," presented at the Conference on Dynamics Days, University of California, San '''Brief version of LBL-15202. Diego, Jan. 5-7, 1982.

1982 PUBLICATIONS AND REPORTS LBL Reports

Refgreed Journals 1. Carson Jeffries and Jose Perez, "Direct Ob servation of Crises of the Chaotic Attractor in a 1. James Testa, Jose Perez, and Carson Jeffries, Nonlinear Oscillator," Phys- Rev. A, in press, "Evidence for Universal Chaotic Behavior of a LBL-14653. Driven Nonlinear Oscillator," Phys. R2V. Lett. 48, 714 (182); LBL-13884, 2. James Testa and G. A. Held, "Period Onubling, Bifurcations, Chaos, and Periodic Windows cf the 2. Jose Perez and Carson Jeffries, "Effects of Cubic Map," LBL-14559. Adoitive Noise on a Nonlinear Oscillator Exhibit ing Period Doubling and Chaotic Behavior," Phys. 3. James Testa, Jose Perez, and Carson Jeffries, Rev. B 26, 3460 (1982); LBL-14208. "Evidence for Bifurcation and Universal Chaotic Behavior in Nonlinear Semiconducting Devices," LBL-13719. 3. Carson Jeffries and Jose Perez, "Observation of a Pomeau-Manneville Intermittent Route to Chaos 4. E. J. Pakulis, E. E. Haller, and C. D. in a Nonlinear Oscillator," Phys. Rev. A ^6, 2117 Jeffries, "EPR of the Lithium Ion-Dangling Bond (1932). Complex in Germanium Containing Dislocations," Sol. St;t2 Comm., in press, LBL-14836. 4. James Testa, Jose Perez, and Carson Jeffries, "Testa, Perez, and Jeffries Respond," Phys. Rev. 5. E. J. Pakulis, "Electrically Detected Elec Lett. _49, 1055 (1982); LBL-150B2. tron Paramagnetic Resonance in Germanium Single Crystals," submitted to J. Mag. Res., L8L-14802. 5. Jose Perez and Carson Jeffries, "Direct Ob servation of a Tangent Bifurcation in a Nonlinear 6. E. J. Pakulis, "EPR at Dislocations in Ger Oscillator," Phys. Lett. 92A, 82 (1982); LBL-14633. manium," Ph.D. thesis, LBL-14664.

6. S. M. Kelso, "The Strain-Confined Electron- 7. George Gibson and Carson Jeffries, "Observa Hole Liqjid in Ge: Density Variations and Com tion of Period Doubling and Chaos in Spin Wave pressibility," Phys. Rev. B 26, 591 (1982); Instabilities in Yttrium Iron Garnet," LBL-15202. LBL-13911. 7. S. M. Kelso, "Energy- and Stress-Dependent Invited Talks Hole Masses in Germanium and Silicon," Phys. Rev. B 2S, 1116 (1982); LBL-12854. Colloquia given by Carson Jeffries on various aspects of universal chaotic behavior in solids: 8. S. M. Kelso, "Calculation of Properties of the Electron Hole Liquid in Uniaxially Stressed Ge and University of California, Santa Cruz, Physics Si," Phys. Rev. B 25, 763 (1982); LBL-13387. Colloquium, February 4, 1982.

9. J. C. Culbertson and J. E. Fi,rneaux, "Density Institute of Theoretical Physics Colloquium, Univ. Dependence of an Electron-Hole Liquid Correlation of Calif., Santa Barbara, February 18, 1982. Factor in Ge: Experiment," Phys. Rev. Lett. ^9, 1528 (1982); LBL-14424. Xerox Palo Alto Research Laboratory Colloquium, April 23, 1982.

Other Publications Stanford University, Dept. of Chemical Engineering Colloquium, April 28, 1982. 1. Carson Jeffries, "Routes to Chaos," Physics News in 1982, American Institute of Physics (New Stanford University, Div. of Applied Physics Sem York), in press. inar, October 21, 1982.

2. J. E. Furneaux, J. C. Culbertson, E. E. Hal- Harvard University, Physics Dept. Colloquium, ler, "A Mechanism for Electron-Hole Droplet Pinn October 25, 1982. ing in Ge," BAPS .27, 320 (1982). Bell Telephone Labs, Murray Hill, Seminar, 3. J. C. Culbertson and j. E. Furneaux, "Density October 26, 1982. Dependence of the Electron-Hole Liquid Enhance ment Factor in Ge," BAPS 27, 321 (1982); LBL-13688. University of Illinois, Urbana, Nonlinear Dynamics Seminar, October 27, 1982. 4. E. J. PafcuHs and C. D. Jeffries. "Electric Detection of Magnetic Resonance at Dislocations University of Illinois, Urbana, Physics Collo in Ge," BAPS £7, 144 (1982); LBL-13631. quium, October 28, 1982. 5. C. D. Jeffries, "Observation of Periodic Win Purdue University, Phvsics Seminar, October 29, dows in the Chaotic Regime of a Nonlinear Semi 1982. d. Tlme-RModmd Spectroscopics in Spuds*

Peter V. Yu, Investigator

1. NONEQUIUBRIUM PHONON SPECTROSCOPY IN GaAst 109 eV/cm. Previously this deformation poten tial had been estimated only indirectly from Gunn C. L. Collins and P. Y. Yu oscillations in GaAs. Our technique is much more direct and precise than the 6unn effect in deter It is we'l known that hot electrons in GaAs mining the interval ley scattering rates and the will relax extremely rapidly (in -0.1 psec) by energy of the X minima. Extension of this work emission of longitudinal optical (LO) photons. to study other semiconductors is in progress now. On the other hand, the LO phonon lifetime is ~10 psec at low temperature. Tiese facts suggest * * * that if one excites hot carriers in GaAs with a picosecond laser pulse, a transient nonequilib- +Brief version of LBL-1499Z. rium LO phonon population lasting for -10 psec can be excited. We have studied this nonequilibrium LO phonon population, using Raman scattering 2. LIFETIME OF ORTHO-EXCITON AKD ORTHO-TO with a picosecond laser pulse. In the experiment PARA-EXCITON CONVERSION IN Cu^f a GaAs sample is excited by a train of picosecond dye laser pulses. If the kinetic energy of the J. S. Weiner, N. Caswell,J and P. Y. Yu photoexcited hot carrier is much larger than the LO phonon energy, one expects that several LO CugO is a classical semiconductor for study photons can be emitted by one hot carrier so we ing properties of excitons, which are bound states predict that Ng, the number of LO phonons ex of electrons and holes and are ;.'„c,, thought of cited, should increase with the excitation photon as analogues of positronium in a solid. In Cu£0 energy. This prediction is verified by Mie ex as many as 13 Rydberg states of its exciton have perimental result in Fig. 1.1, where tne solid been observed in absorption. Optical dipole circles are the experimental points and the curve transitions to the lowest Is state of the exciton is calculated using the empirical pseudopotential in CugO is forbidden by parity, so it is ex band structure of GaAs obtained by Professor M. pected that the lifetime of this state in CujO L. Cohen and co-workers. The interesting feature should be very long (>1 usee). However, previous in Fig. 1.1 is the abrupt drop in the phonon oc attempts to measure its lifetime with nanosecond- cupation number for photon energy £2.1 eV. Our long laser pulses have not been successful. theory explains this decrease as due to scatter ing of the hot carriers from the r-valley to the X-valleys. Furthermore, we find the r-X inter- We have utilized a modelocked picosecond dye valley deformation potential in GaAs to be 1.1 x laser in conjunction with a delayed coincidence photon counting system to determine the lifetime of the Is excitons in CU2O. He found that the triplet state of the Is exciton (known as the ortho-exciton) has a lifetime of <2.5 nsec which is limited by its decay into the para-exciton (singlet state of the Is exciton). The para-ex citon lifetime is determined by recombination at impurities so it can vary between <10 nsec end 13 iisec. The conversion of ortho-excitons to para- excitons is found to be dependent on temperature as T3''. A comparison with existing theories shows that none of them can account for this T3/2 dependence. ISO 1.90 2.00 2.10 EXCITATION PHOTON ENERGY C«V> TThis work was supported in part by the Director,

Fig. 1.1. LO phonon population Nq in GaAs Office of Energy Research, Office of Basic Energy plotted as a function of excitation photon Science, Materials Sciences Division of the energy. The solid circles are experimental U. S. Department of Energy under Contract No. points while the solid curve is the result of a 0E-AC03-76SF0CO98 and the National Science Grant model calculation. The arrows labeled as r-L and No. DMR79-19463. r-X represents, respectively, the photon energies ^Present address: IBM T. J. Watson Research for the onset of r to L and r to X-ir.tervalley Center, Yorktown Heights, NY 10598. scatterings according to pseudopotential band structure calculation. (XBL 831-7973) 1982 PUBLICATIONS AND REPORTS

Refereed Journals *This work was supported by the Director, Office of Energy Research, Office of Basic Energy 1. N. Caswell and P. Y. Yu, "Physical Origin of Sciences, Materials Sciences U'vision of the U.S. the unomalous Temperature Dependence of the Is Department of Energy under Contract No. Yellow Exciton Luminescence Intensity in CuaO," DE-AC03-76SF00098. Phys. Rev. B. 25, 5519 (1982). 86

LBL Reports 2. 0. S. Meiner and P. Y. Yu, "Lifetime of Pho- toexcited Carriers in Pure GaAs, GaAs:Cr, and 1. C. L. Collins and P. Y. Yu, "Nonequilibrium GaAs:0," Bull. Am. Phys. Soc. 27, 335 (1982), Phonon Spectroscopy: A New Technique for Study LBL-13757. ~ ing Intervalley Scattering in Semiconductors," LBl-14992. Invited Talks 2. J. S. Weiner, N. Caswell, p. Y. Yu, and A. Mysyrowicz, "Orthoto Para-Exciton Conversion 1n 1. P. Y. Yu, "Some Picosecond Laser Experiments CogO: A Subnanosecond Time Resolved Photo- luminescence Study," LBL-15350. in GaAs," Quantum Electronics Seminar, Dept. of Electrical Engineering of Computer Science, UC-Berkeley, April 14, 1982. Other Publications

1. N. Caswell and P. Y. Yu, "Physical Model for 2. P. Y. Yu, "Picosecond Laser Spectroscopies in the Temperature Dependence of the CU2O Yellow Semiconductors," Cavendish Laboratory, Cambridge, Exciton Luminescence Intensity," Bull. Am. Phys. August 26, 1982. Soc. 27, 175 (1982). 87

e. Superconductivity, Superconducting Devices, and 1/1 Notoe*

John Clarke, Investigator

1. CHAOS IN JOSEPHSON JUNCTIONS''' , .-, , 1 R. F. Miracky, R. H. Koch, and J. Clarke (o) There has been increased interest over the past several years in the properties of nonlin ear differential equations and physical systems described by such equations. Under appropriate A circumstances, such systems exhibit chaos, a special, aperiodic solution tc the governing equations that appears experimentally as broad band noise. However, most physical systems are too complicated to be represented by models suit able for analytical or numerical methods. The Josephson junction is a notable exception and is 1 p thus an excellent system for studies of chaotic i behavior. 00 ' We have studied Josephson tunnel junctions fabricated to exhibit chaotic behavior. Each junction is shunted with its self-capacitance and an external resistance with substantial self-in ductance. The equation of motion of this system, when biased with a constant current, is third order and nonlinear in the phase difference across the junction and is therefore expected to exhibit chaos. We have modeled this system using SYSTEM analog and digital computers, with parameters NOISE LEVEL-, chosen to approximate those of the tunnel junc tions. I i

Experiments performed on these junctions re FREQUENCY IHj) veal two phenomena. First, the current-voltage characteristics exhibit stable regions of nega tive resistance. Second, measurements of the low — .1 frequency voltage noise as a function of bias cur (c) rent show excessively noisy intervals, usually in the vicinity of the negative resistance regions, separated by low-noise regions. We have identi fied this excess noise as arising from two dif ferent mechanisms: chaos, characterized by noise temperatures Tpj of about 103 K; and switching between subharmonic modes, with Ty Z 106 K. Rep resentative voltage spectral densities from the analog are given in Fig. 1.1a and b. In Fig. 1.1a, which represents a chaotic region, the low frequency noise has a temperature of about 800 K, independent of whether or not thermal noise is present in the shunt resistor. Figure 1.1b shows the spectral density of the noise in a switching regime, with a noise temperature of over 10^ K when thermal noise equivalent to about 3 K is 335 377 present in the resistor. When this thermal noise FREQUENCY (MHz) is removed, the switching ceases, and the noise from the simulator becomes too low to be meas Fig. 1.1. Spectral density of voltage noise from ured. Figure 1.1c shows the spectral density of analog in (a) chaotic regime and (b) switching the high frequency noise from a real junction and regime with ( ) and without (—) 3 K ther shows clearly the two metastable subharmonic modes mal noise in shunt resistor, (c) SONS two sub between which the junction switches, producing a harmonic modes in real junction between which the low frequency noise of over 10° K. system switches to produce large levels of low frequency noise. (XBB 820-9646A)

To calculate the noise temperature of a volt age amplifier involving a dc superconducting quantum interference device (SQUID) one needs to .know the flux-to-voltage transfer function, V

The SQUID were fabricated from thin films in a planar configuration, tightly coupled to a 50-turn superconducting spiral input coil. The shunt re sistance of the SQUID on which noise measurements were made was two orders of magnitude lower than usual so as to enhance the magnitude of the cur rent noise. The coil of this SQUID was coupled to the coil of a second SQUID, which was then used to measure the current noise. The voltage across the first SQUID was measured with a cooled resonant tank circuit coupled to a low noise pre amplifier, and the cross correlation between the */*n current and voltage noises was measured with a Fig. 2.1. IVj, Y , TJ and «r for real spectrum analyzer. An analog simulation of the V VJ SQUID was also fabricated and used to predict the SQUID (x) and analog SQUID ( ) with the same performance of the real SQUID. parameters. (*0 is the flux quantum, I0 and R are the critical current and resistance of each The results are shown in Fig. 2.1, where the junction, and the y's are the dimensionless spec measured values of |V^|/(I0R/*0), YV, YJ, and Yvj tral densities of the noises normalized to th'; Johnson noise in the resistive shunts.) are plotted vs 0. The results are in good agreement with the predictions of the analog sim {XBL 831-5084) ulator. From these measurements, we can calcu late the noise temperature of the SQUID used as an amplifier with a tuned input circuit and find 3. CORRELATION LENGTHS IN MAGNETOTELLURICS* Tfo * 10_6(f/l Hz) K. The corresponding value for a SQUID with the usual values of the shunt resis w. M. Goubau, P. Maxton, and J. Clarke tors is about 10-8(f/i Hz) K. In the magnetotelluric method, one determines * * + the impedance tensor of the ground, Z(w), by simultaneously measuring the orthogonal horizontal +Brief version of LBL-15313. components of the fluctuating magnetic and elec- 89

trie fields H*(a>) and I(u). These fluctuations are generated in the magnetosphere and propagate to the earth's surface approximately as plane waves. The magnetic field fluctuations can be measured with SQUID magnetometers, while the elec tric field fluctuations are measured by means of ^^ buried electrodes. The method is widely used in geophysical prospecting for geothermal sources, oil deposits, and other natural resources. A significant advance in the technique was the in Remote Ref troduction by this group of the remote reference Local Ref technique in which the two horizontal components AuioPef of the magnetic field are measured by a second, 2m remote magnetometer. The signals are telemetered to the base station and used to lock-in detect f ; the magneto-«*11 uric signals. This technique has resulted in a major improvement in the quality of | magnetotelluric data. However, the minimum nec essary separation of the base and remote stations has never been established—separations of 5 km or more are typically used—and the purpose of this investigation was to establish this length. i

I The site chosen was near Mount Hamilton* Cali fornia. A base station consisting of a two-axis SQUID magnetometer and buried electrodes was es tablished, as was a remote reference SQUID mag netometer, with telemetry to the base station. A third SQUID magnetometer was then used as a local reference; its separation from the base magnetometer was varied between 2 and 400 m. ^=r=^ Signals from the local reference were trans -7- mitted to the base station via coaxial cables. Data from the buried electrodes and three mag netometers were collected simultaneously. The impedance tensor was then calculated using the ''' 200 m remote reference, the local reference, and using the least squares technique on data from the base magnetometer alone (i.e., autc-reference).

The results are shown in Fig. 3.1, where the Fig. 3.1. Apparent resistivity vs period using apparent resistivity in a particular direction is remote, local, and auto-referenre techniques for plotted vs period for each v\ the three methods three separations of the base magnetometer and and for three separations between the base and the local reference magnetometer. (XB1 831-5085) loca'. reference. We see immediately that the remote and local reference methods yield substan tially higher quality data than the auto-refer 1982 PUBLICATIONS AND REPORTS ence. The discrepancies between the local and remote references are small but significant at Refereed Journals the 2 and 100 m separations, and have disappeared by the time the separation has been increased to 1. T. D. Gamble, U. H. Goubau, R. Miracky, and 200 m. This result has important consequencies J. Clarke, "Hagnetotelluric Regional Strike," for surveying, implying that the magnetic fields from stations only (say) 1 km apart can be used Geophys. Zh. 932 (1982); LBL-10846. as referer.ee signals. Thus, remote referenced data cs:< be collected at two nearby sites simul 2. D. J. Van Harlingen, R. H. Koch, and taneously, without the need for a relatively dis J. Clarke, "Superconducting Quantum Interference tant reference magnetometer, thereby doubling the Device with Very Low Magnetic Flux Noise Energy," rate at which an area can be surveyed. Appl. Phys. Lett. 41, 197 (1982); LBL-13668. 3. R. H. Koch, 0. J. Van Harlingen, and J. Clarke, "Measurements of Quantum Noise in Resistively Shunted Josephson Junctions," Phys. tBrief version of LBl-15484. Rev. 8 26, 74 (1982); LBL-13326. 9D

4. R. H. Koch, D. J. Van Harlingen, and ics, University of California, Santa Bar^dra, J. Clarice, "Observation of Quantum Noise in a November 18, 1981. Resistively Shunted Josephson Junction," Physica B and C 109 h UO, 2055 {1982); LBL-13748. 3. R. H. Koch and J. Clarke, "Chaotic Noise Observed in Current-Biased Josephson Junctions Other Publications Shunted with a Resistance in Series with an In ductance," Dynamic Days, La Jolla Institute, La 1. J. Clarke and P. L. Richards, "Quantum Noise Jolla, California, January 5-7, 1982. in Superconducting Tunnel Junctions," Physics News in 1981, p. 37. 4. D. Seligson and J. Clarke, "Phonon-Induced Enhancement of the Energy Gap and Critical Cur 2. J. Clarke, "Superconducting Devices," in rent of Superconducting Aluminum Films," 1982 Concise Encyclopedia of Sciences and Technology, March Meeting of the American Physical Society, edited by R. G. Lemer and G. L. Trigg, Addison- Dallas, Texas. Wesley, Reading, Massachusetts, 1982, p. 263; LBL-12135. 5. R. H. Koch, J. M. Martinis, and J. Clarke, "Measurements of Chaotic Noise in Current-Biased 3. R. H. Koch, J. H. Martinis, and J. Clarke, Josephson Junctions Shunted with a Resistance and "Measurement;* of Chaotic Noise in Current-Biased an Inductance in Series," 1982 March Meeting of Josephson Junctions Shunted with a Resistance and the American Physical Society, Dallas, Texas. an Inductance in Series," Bull. Am. Phys. Soc. 27, 266 (1982); LBL-13750 Abs. 6. J. Clarke, "SQUIDs and Geophysics," Physics Division Colloquium, Los Alamos Scientific Labo 4. D. Seligson and J. Clarke, "Phonon-Induced ratory, Los Alamos, New Mexico, May 6, 1982. Enhancement of the Energy Gap and Critical Cur rent of Superconducting Aluminum Films," Bull. 7. J. Clarke, "SQUIDs," Low Energy Physics, Am. Phys. Soc. £7, 252 (1982); LBL-13749 Abs. Quarks, SQUIDs* and the Cosmos Conference, University of California, Oavis, California, May 5. J. Clarke, "SQUID," McGraw-Hill Encyclopedia 16, 1982. of Sciences and Technology, 1982, p. 28; LBL-12136. 8. J. Clarke, "Applications of SQUIDs," NATO Summer School yn Superionic Conductors, Erice, 6. J. Clarke, "Superconducting Devices," Sicily, July 10, 1982. McGraw-Hill Encyclopedia of Sciences and Technology, 1982, p. 339; LBL-12136. 9. J. Clarke, "The Limits of SquiD Technology I," NATO Summer School on Advances in Supercon 7. W, M. Goubau. N. C. Goldstein, and J. Clarke, ductivity, Erice, Sicily, July 12, 1982. "Magnetotelluric Studies at the Cerro Prieto Geo- thermal Field," Proceedings of the 3rd Symposium 10. J. Clarke, "The Limits of SQUID Technology on the Cerro P.-ietc Geothermal Field, Baja Cali II," NATO Summer School on Advances in Supercon fornia, Mexicj, March 24-26, 1981, p. 357; ductivity, Erice, Sicily, July 13, 1982. LBL-11967, published in 1982. 11. J. Clarke, "Experiments on Chaos in Josephson LBL Reports Junctions," Gordon Conference in Quantum Solids and Fluids, Plymouth, New Hampshire, July 19, 1. J. Clarke, "'undamental Limits on SQUID 1982. Technology," LBL-14972. 12. J. Clarke, "Chaos in Josephson Junctions," 2. R. H. Koch, J. Clarke, W. M. Goubau, J. K Bell Laboratories, Murray Hill, New Jersey, July Martinis, C. M. Pegrum, and D. J. Van Harlingen, 26, 1982. "Flicker (1/f) Noise in Tunnel Junction DC SQUIDS," LBL-14973. 13. J. Clarke, "Quantum Noise in Josephson Junc 3. J. Clarke, "Geophysical Applications of tions and SQUiuS," Oak Ridge National Laboratory, SQUlDs," LBL-15312. Oak Ridge, Tennessee, November 29, 1982.

4. J. M. Martinis and J. Clarke, "Measurements 14. J. Clarke, "Geophysical Applications of of Current Noise in DC SQUIDs," LBL-15313. SQUIDs," 1982 Applied Superconductivity Con ference, Knoxville, Tennessee, November 30 - 5. R. H. Koch, J. Clarke, J. M. Martinis, W. M. December 3, 1982. Goubau, C. M. Pegrum, and 0. J. Van Harlingen, "Investigation of 1/f Noise in Tunnel Junction DC 15. J. M. Martinis and J. Clarke. "Measurements SQUIDs," LBL-15314. of Current Noise in DC SQUIDs," 1982 Applied Superconductivity Conference, Knoxville, Invited Talks Tennessee, November 30 - December 3, 1982.

1. J. Clarke, "Quantum Noise in Josaphson Junc 16. R. H. Koch, J. Clarke, J. M. Martinis, W. M. tions d SQUIDs," Department of Applied Science, Goubau, C. M. Pegrum, and D. J. Van Harlingen, Stan-' Mniversity, November 5, 1981. "Investigation of 1/f Noise in Tunnel Junction DC SQUIDs," 1982 Applied Superconductivity Con 2. J. Clarke, "Quantum Noise in Jose^iion Junc ference, Knoxville, Tennessee, November 30 - tions and SQUIDs," Institute for Theoretical Phys December 3, 1982. 6. Theoretical Research

a. Theoretic*! Studies ol the Electronic Properties of Solid Surfaces* Leo M. Falicov, Investigator

Introduction. The purpose of this program is The purpose of this research was to investigate to study properties of solid surfaces. In these apparently contradictory results and to re-" particular the interest is in determining: solve the controversy. In a series of papers1 (a) structural properties of surfaces, namely, self-consistent calculations of the electronic the organization and arrangement of atomic con structure and the ma'^tuatian of Ni, NiCu stituents at equilibrium; (b) constitutional interfaces, Ni overlayers on Cu, and in general properties of the surface, in particular the Ni overlayers have been carried out. segregation properties of alloys at the surface as a function of crystal structure, surface ori It is found that magnetization is suppressed entation, nominal chemical composition and tem in the Ni-Cu or Ni-simple metal interfaces, but perature; (c) electronic structure of surfaces, enhanced in either the Ni surface or in isolated in particular electron states and electron densi Ni thin films. The net effect of this competi ties in the neighborhood of the surface; tion is that a Ni monolayer is substantially (d) vibronic properties of surfaces; (e) magnetic magnetic on Cu(100) but paramagnetic (or nearly properties of surface, both in magnetic solids so) on Cu(lU). Film magnetization is found to (ferromagnetic and antiferromagnetic) or in non be very sensitive to substrate composition. For magnetic solids that may develop a magnetic sur substrates which couple strongly to the Ni film, face layer; and (f) chemical—in particular the ferromagnetism first appears at about three atomic catalytic—properties of solids as they are layer Ni, in quantitative agreement with experi related to basic physical properties (a)-(e). ments based on Al and Pb-Bi substrates. The cru cial mechanism acting to suppress Ni magnetization is sp_-d hybridization. Figure 1.1 shows the mag A variety of theoretical techniques and models net izaTion at the various atomic layers of Ni to focus on the various properties (band-structure ovsrlayers of various thicknesses on any metal models, many-body electron physics, numerical that couples strongly to the Ni electrons. The relaxation techniques) are developed, but the results are striking and in good agreement with emphasis is on physical aspects and their impli experiment: Overlayers of up to two atom thick cation to experiments rather than techniques £er ness are "dead." Overlayers thicker than two se. atoms are fully magnetic, with the magnetization enhanced at the free surface and completely quenched at the interface. 1. MAGNETIC AND ELECTRONIC PROPERTIES OF Ni FILMS, SURFACES, AND INTERFACES Strong Coupling L. M. Falicov and Jerry D. Tersoff

The problem of magnetism on Ni surfaces, Ni interfaces, and over layers of Ni on a variety of other nonmagnetic metals has been an open problem for a long time. Reports of "dead layers," i.e., layers which are nonmagnetic, have been abundant in the literature. This seems to indicate that the ?- .face of Ni contains up to two atomic layers in which the magnetism is quenched. The reports, however, are not consistent with one another, and the various experiments have been done by measur ing the total magnetization of relatively thin films of Ni deposits on a variety of mostly poorly characterized substrates. Recent experiments, however, as well as a few first-principle calcu lations, seem to indicate that the surface layer of pure Ni metals is either fully magnetic, has its magnetism only very slightly reduced, or even has a small enhancement of its magnetization. 3 4 5 Ni atomic layers Fig. X.l. The magnetization of Ni overlayers an a strongly coupled metallic substrate. The ab scissa indicates the thickness {in atoms) of the •This work was supported by the Director, Office Ni overlayer. The ordinate is the magnetization of Energy Research, Office of Basic Energy of each atomic layer. Triangles correspond to Sciences, Materials Sciences Division of the U.S. the surface (free) layer, squares are the inter Department of Energy under Contract No. face layer, and circles correspond to layers in DE-AC03-76SF00098. between. (XBL 832-8068) 7. J. Tersoff and L. M. Falicov, "Calculation of * * * Magnetization in Ordered Ni-Cu Alloys," Phys. 1. L. H. Falicov and J. Tersoff, Phys. Rev. B Rev. B_25, 4937 (1982); LBL-13625. 25, 2959 (1982); Phys. Rev. B .26, 469 (1982); PTTys. Rev. B 26, 6186 (1982). t8. J. Testa and L. M. Falicov, MTwo-Band Model of Itinerant Magnetism," Am. J. Phys. 50, 647 (1982). ~" 2. THERMODYNAMIC PROPERTIES OF Li INTERCALATED AND DISORDERED LAYER COMPOUNDS 9. J. Tersoff and L. M. Falicov, "Presence and Absence of Magnetism in Thin Ni Films," Phys. L. M. Falicov and R. Ostfrio Rev. B 26, 459 (1982); LBL-13958.

The electrochemical properties of Li intercala 10. J. Tersoff and L. M. Falicov, "spod Charge tion in TayTij.ySg have been the subject of inten Transfer at Transition- and Noble-Metal Surfaces: sive experimental studies. The structure in the A Reply," Phys. Rev. B 26, 105B (1982); LBL-14363. "incremental capacity" is difficult to understand and shows signs of strong correlation between the +11. J. L. Mora'n-Lopez and L. M. Falicov, "Self- Li ions themselves, and between the position of Consistent Model of Hydrogen Chemisorption on the Li ions and the composition of the disordered Ferromagnetic Transition Metals," Phys. Rev. B structure. 26, 2560 (1982).

We have completed a mean-field approximation 12. J. Tersoff and L. M. Falicov, "Magnetic and calculation1 applied to a triangular-lattice Electronic Properties of Ni Films, Surfat.es, and gas model with three different randomly distribu Interfaces," Phys. Rev. B 26, 6186 (1982); ted sites and nearest-neighbor interaction between LBL-14507. the gas particles. This represents well the sys tem under consideration. Ground-state diagrams 13. R. Ostfrio and L. M. Falicov, "Effect of show various sequences of ordered phases. Finite Disorder on the Li Intercalation Properties of

temperature results show minima in the "incremen LixTavTii_yS2: A Mean-Field Theory, J. Chain. tal capacity" curves because of nearly complete Phys. 2i» 6218 (1982); LBL-14816. filling of sites of a given chemical type. The model is good for those alloys where the experi +14. M. J. Pinto and B. Koiller, "Optical Proper mental results suggest a disordered distribution ties of Crystals with Impurities," J. Phys. C 15, of Li atoms. 7229 (1982). ~~

* * * L8L Reports

1. L. M. Falicov and R. Ostfrio, J. Chem. Phys. 1. J. Tersoff, "Electronic, Magnetic and Chemical J7, 6218 (1?82). Properties of Films, Surfaces and Alloys," Ph.D- thesis, LBL-14484.

1982 PUBLICATIONS AND REPORTS 2. R. Ostfrio, "The Two-Dimensional Triangular Lattice and Its Application to Lithium Inter Refereed Journals calated Layered Compounds," Ph.D. thesis, LBL-14815. +1. M. Kiwi, T. H. Lin, and L. M. Falicov, "Antiferromagnetism, Projected Density of States Other Publications and the Bogoliubov Transformation for Bosons," Phys. Rev. B 25, 432 (1982). 1. L. M. Falicov, "Spin Waves at Surfaces and Steps in Ferromagnets and Antiferromagnets," in 2. R, Ostfrio and L. M. Falicov, "Cluster- Excitations in Disordered Systems, edited by Variation Method for the Triangular Lattice Gas," M. F. Thorpe, Plenum Press, New York, 1982, J. Phys. Chem. Solids 43, 73 (1982); LBL-11474 p. 489. and LBL-11475. ~~ 2. J. L. MorSn-LGpez and L. M. Falicov, +3. L. M. Falicov and B. Joo*s, "Potential of a "Magr.Ltic Excitations at the Surface of Alloys Positive Test Charge in Germanium: Application with Magnetic Components," in Excitations in to Hydrogen," Phil. Mag. 45, 255 (1982). Disordered Systems, edited by M. F. Thorpe, Plenum Press, New York, 1982, p. 501. t4. M. Robbins and L. M. Falicov, "Electronic Theory of Ordering and Segregation in Binary +3. L. H. Falicov and M. Robbins, "Theory of Alloys: Application to Simple Metals," Phys. Ordering and Segregation in Binary Alloys: Rev. B 25, 2343 (1982). Application to Alkali and Noble Metals," in Excitations in Disordered Systems, edited by 5. J. Tersoff and L. M. Falicov, "Interface M. F. Thorpe, Plenum Press, New York, 1982, Magnetization: Cu Films on Ni(100)," Phys. Rev. p. 613. B 25, 2959 (1982); LBL-13624. +4. L. M. Falicov, "Summary: Disordered Systems +6. J. L. MoraVLtfpez and L. M. Falicov, "Theory in Perspective," in Excitations in Disordered of Hydrogen Chemisorption," J. Vac. Sci. Technol. Systems, edited by M. F. Thorpe, Plenum Press, 20, 831 (1982). New York, 1982, p. 677. 93

5. J. Tersoff and L. M. Falicov, "Calculations 3. L. M. Falicov, "Electrical, Magnetic and of Magnetization in Ni- on Cu- and Cu-on-Ni Film Chemical Properties of Ni Overlayers," Seminaire Systems," Bull. Am. Phys. Soc. J7, 153 (1982). de Physique des Sol ides, L.M.S.E.S., France, July 2, 1982. t6. M. Robbins and L. H. Falicov, "Total Energies and Short-Range Order in Transition-Metal Alloys," 4. L. M. Falicov, "Electronic, Magnetic, and Bull. Am. Phys. Soc. 2£, 186 (1982). Chemical Properties of Nickel Overlayers," Seminar at General Motors Research Laboratories, Warren, 7. L. M. Falicov and J. Tersoff, "Calculations Michigan, July 22, 1982. of Magnetization in Artificial Ordered Ni-Cu Alloys," Bull. Am. Phys. Soc. 27, 214 (1982). 5. J. L. Morfn-ltfpez and L. M. Falicov, "Theory of Surface Effects in Binary Alloys," Symposium Invited Talks on Alloys Phase Diagrams, Materials Research Society Meeting, Boston, Massachusetts, 1. L. M. Falicov, "Electronic, Chemical and November 1, 1982. Magnetic Properties of Metallic Overlayers," Materials and Molecular Research Division Annual 6. M. 0. Robbins and I. M. Falicov, "Electronic Review Symposium, Lawrence Berkeley Laboratory, Energy and Short-Rang? Order in Binary Alloys," February 8, 1982. Symposium on Alloys Phase Diagrams, Materials Research Society Meeting, Boston, Massachusetts, 2. L. M. Falicov, "Theory of Hydrogen Chemisorp- November 1, 1982. tion on Ferromagnetic Transition Metals," Inter national Symposium on the Electronic Structure * * * and Properties of Hydrogen in Metals, Richmond, 1Work supported in part by the National Science Virginia, March 6, 1982. Foundation through Grant DMR81-06494. 94

b. Theoretical SoKd Stat* Physics* Marvin L Cohen, Investigator

Introduction. In addition to developing 2. CRYSTAL STRUCTURE"1" general theories and techniques for studying the properties of solids, solid state theorists are M. Y. Chou, S. Froyen, Pui K. Lam, M. T. Yin, and now able to calculate the properties of real Marvin L. Cohen materials. The necessary ingredients are quantum mechanics, a theory of how electrons interact For the first time, it has become possible to with each other and with atomic ions in a crys calculate accurately the crystal structure of tal, and a technique for computing properties solids. The first examples of successes for this that can be measured. In the description below, method involve the semiconductors Si and Ge. The specific applications to solid surfaces, crystal current extensions are to diamond, beryllium, and structure, lattice dynamics, and electronic compound semiconductors. structure are described.' Much of the work is based on the use of a pseudopotential to repre The method involved in these calculations sent the interaction between the electrons and consists of an evaluation of the total energy of ions, and a method for computing the total energy a solid in an assumed configuration. The total of the solid. energy is then compared for various structures, and a minimum energy structure is assumed to correspond to the actual structure. One limita 1. SOLID SURFACES7 tion of this method is that it requires a subset of likely structures as input. The only other John E. Northrup and Marvin L. Cohen input to the calculation is the atomic number.

One of the most important problems in surface The results for the materials investigated are physics is the determination of the structure of consistent with experiment. Lattice constants, Si(111). This surface is the most studied sur bulk moduli, cohesive energies, and other proper face in science. However, a detailed description ties are computed. A major focus of this research of its atomic arrangement and electronic struc is the prediction of stable structures at high ture is still lacking. pressure. A significe.nt amount of effort was made to compute high-pressure forms of III—V semi An attempt to calculate the atomic positions conductors. Although the experimental results are and electronic structure was made. To compute sparse, there is some agreement for the structure the surface atomic arrangement, the forces on all and transition pressure between theory and exper the atoms were calculated as a function of the iment. This work is being expanded with the hope positions of the atoms. By moving atoms near the that high-pressure structures will be predicted surface in the direction of the residual forces successfully. found, a minimum energy configuration could be obtained. It was necessary to include the effects of spin in these calculations. TBrief version of Phys. Rev. B 24, 6121 (1981), The results were two-fold: for a 1 x 1 Solid State Comm. 42, 861 (198277 Solid State geometry it was found that the lowest energy Comm. 43, 447 (19871", and Phys. Rev, B 26, 5668 structure is spin polarized; for a 2 x 1 geometry (1982). the lowest energy structure was found to be simi lar to a chain model proposed by Pandey, The 1 x 1 structure is stable against buckling distor 3. LATTICE DYNAMICS7 tions and is antiferromagnetic. The 2x1 con figuration has lower energy, and the calculated Pui K. Lam, M. T. Yin, and Marvin L. Cohen electronic structure agrees well with the corre sponding angle-resolved photoemission experi In the past the calculation of the vibrational mental results. structure of solids often involved the use of empirical parameters. Recently an afr initio approach was developed which is an outgrowth of the total energy formalism discussed above. The TBrief version of Phys. Rev. Lett. 47, 1910 method involves a calculation of the total energy (1981), J. Vac. Sci. Technol. 21, 333~(i982), and for an undistorted crystal and for a crystal con Phys. Rev. Lett. 49, 1349 [1987J. taining a frozen-in distortion corresponding to a phonon. A comparison of these two cases yields the energy of the phonon or lattice vibration of interest. *This work was supported by the Director, Office of Energy Research, Office of Basic Enorqy The applications of this method have been made Sciences, Materials Sciences Division of the U.S. to Si, Ge, and Al. At first it was only possible Department of F.nergy under Contract No. to calculate the lattice vibrational frequencies DE-AC03-76SF0u098 and also by the National at specific wavevectors in the Brillouin zone. A Science Foui.-lation Grant No. DMR7822465. recent development involves the computation of 95

force constants determined by computing the for 1982 PUBLICATIONS AND REPORTS ces on atoms arising from the displacement of a plane of atoms. This method allows the calcula Refereed Journals tion of the frequency of the lattice vibration as a function of wavevector along a symmetry line in 1. John E. Northrup, Marvin L. Cohen, J. R. the Brillouin zone. Chelikowsky, J. Spence, and A. 01 sen, "Electronic Structure of the Unreconstructed 30" Partial The applications to Si, Ge, and Al have been Dislocation in Silicon," Phys. Rev. B 24, 4623 successful. In addition to yielding the frequen (1981). — cies of the vibrations, the pressure coefficients of the vibrational modes have also been deter 2. M. T. Yin and Marvin L. Cohen, "Ground-state mined. This ab initio approach requires only the Properties of Diamond," Phys. Rev. B 24, 6121 atomic miss, atomic number, and crystal structure. (1981). — * * * 3. John E. Northrup, J. Ihm, and Marvin L. Cohen, "Spin Polarization and Atomic Geometry of fBrief version of Phys. Rev. B 25, 4317 (1982), the Si(lll) Surface," Phys. Rev. Lett. 47, 1910 Phys. Rev. B 25, 5139 (1982), SoTid State Comm. (1981). ~~ 43, 391 (198277 and Phys. Rev. B 26, 3259 (1982). 4. A. K. McMahan, M. T. Yin, and Marvin L. Cohen, "Comparison of Methods for the Calculation of Phase Stability in Silicon," Phys. Rev. 8 24, 4. ELECTRONIC STRUCTURET 7210 (1981). — H. Y. Chou, Pui K. Lam, J. E. Northrup, M. T. 5. Marvin L. Cohen and J. R. Chelikowsky, Yin, and Marvin L. Cohen "Pseudopotentials for Semiconductors," in Hand book on Semiconductors, Vol. 1, edited by Once the crystal structure of a material or w. Paul, North-Holland, Amsterdam, 1982, p. 219. its surface has been determined, it is possible using modern electronic structure techniques to 6. Marvin L. Cohen, V. Heine, and J. C. compute the behavior of the electrons in the Phillips, "The Quantum Mechanics of Materials," crystal. In particular, the electronic band Scientific American 246, 66 (1982). structure, density of states, and charge density can be evaluated. These functions are useful in 7. M. T. Yin and Marvin L. Cohen, "Ab Initio determining the electronic properties of Calculation of the Phonon OispersionT&latlon: materials. Application to Si," Phys. Rev. B 25, 4317 (1982).

The calculations were applied both to ideal 8. Pui K. Lam and Marvin L. Cohen, ",.b Initio materials and solids with defects (i.e., dis Calculation of Phonon Frequencies of fiT," Phys. locations). In general, the results yield good Rev. B 25, 6139 (1982). agreement with experiment, and the calculations often indicate new theoretical solutions and 9. M. Y. Chou, Pui K. Lam, and Marvin L. Cohen, problems. For example, the calculation of the "Ab Initio Calculation of the Static Structural Compton profile of Be gave excellent agreement Properties of Be," Solid State Comm. 42, 861 with experiment; however, a small directionally (1982). — independent difference between the measured and calculated spectra remained. This difference was 10. M. T. Yin and Marvin L. Cohen, "Theory of Ab substantially reduced by incorporating correla Initio Pseudopotential Calculations," Phys. Rev. tion effects. The application of electronic B 25, 7403 (1982). structure theory leads to improvements of the pseudopotential itself and the underlying theory 11. M. T. Yin and Marvin L. Cohen, "Calculation involved in its applications. of the Lattice Dynamical Properties of Ge," Solid State Comm. 43, 391 (1982).

12. S. Froyen and Marvin L. Cohen, "High Pressure +Brief version of Phys. Rev. B 24, 7210 (1981); Phase of III—V Semiconductors: A Microscopic Phys. Rev. Lett. 49, 1452 (198277 Theory," Solid State Comm. 43, 447 (1982).

13. John E. Northrup and Marvin L. Cohen, "Electronic Structure of the n-bonded Chain Model 5. WORK IN PROGRESS and the Nonbuckled Antiferromagnetic Insulator Model for the Si(111) Surface," J. Vac. Sci. The above research will be extended to include Technol. 21, 333 (1982). other materials. In particular, more ionic crys tals will be investigated. Some calculations on 14. Steven G. Louie, S. Froyen, and Marvin L. the electronic structure of alloys of semiconduc Conen, "Nonlinear Ionic Pseudopotentials in Spin- tors are in progress. Compton effect calcula density-functional Calculations," Phys. Rev. B tions for graphite are also in progress. 26, 1738 (1982). 96

15. M. T. Yin and Marvin L. Cohen, "Theory of Invited Talks Lattice-dynamical Properties of Solids: Appli cation to Si and Ge," Phys. Rev. B 26, 3259 1. Marvin L. Cohen, "Pseudopotentials.and Solid (1982). ~~ State Physics," Department of Physics, University of Oregon, February 11, 1982. 16. J. C. Phillips and Marvin L. Cohen, "Molecular Models of Giant Photocontractive 2. Marvin L. Cohen, "Surfaces and Interfaces," Evaporated Chalcogenide Films," Phys. Rev. B 26, Department of Physics, University of Oregon, 3510 (1982). February 12, 1982. 3. Marvin L. Cohen, "Pseudopotentials and Total 17. John E. Northrup and Marvin L. Cohen, Energy Calculations," invited opening plenary "Reconstruction Mechanism and Surface State Dis paper, European Physical Society, Manchester, persion for Si(lll)-2xl," Phys. Rev. Lett. 49, England, March 22, 1982. 1349 (1982). ~~ 4. Marvin L. Cohen, "Pseudopotential 18. M. Y. Chou, Pui K. Lam, Marvin L. Cohen, Calculations for Real Materials," Department of G. Loupias, J. Chomilier, and J. petiau, "Compton Physics, Virginia Polytechnic Institute and State Profile of Beryllium," Phys. Rev. Lett. 49, 1452 University, Blacksburg, VA, April 29, 1982. (1982). ~ 5. Marvin L. Cohen, "Electrons on Solid Surfaces 19. Marvin L. Cohen and T. Geballe, "Novel and Interfaces," Department of Physics, Virginia Superconducting Materials and Mechanisms," in Polytechnic Institute and State University, Superconductivity in d- and f-Band Metals, edited by Blacksburg, VA, April 30, 1982. W. Buckei and W. Weber, Kerntorschungszentrum Karlsruhe GmbH, Karlsruhe, 1982, p. 619. 6. Marvin L. Cohen, "Quantum Mechanical Structure Calculations Using Pseudopotentials," invited opening paper, CALPHAD XI Conference, 20. Marvin L. Cohen, "Pseudopotentials and Total Argonne National Laboratory, Argonne, IL, May 17, Energy Calculations," Physica Scripta Tl, 5 1982. (1982). ~ 7. Marvin L. Cohen, "Pseudopotentials: Past, 21. M. T. Yin and Marvin L. Cohen, "Theory of Present, and Future," combined Physics Colloquium Static Structural Properties, Crystal Stability, for the University of Heidelberg, the University and Phase Transformations: Application to Si and of Karlsruhe, and the Kernforschungszentrum Ge," Phys. Rev. B 26, 5668 (1982). Karlsruhe, Karlsruhe, Germany, June 25, 1982; Max Planck Institute, Stuttgart, Germany, July 1, 1982; Department of Physics, University of Chicago, IL, October 14, 1982; Department of Physics, University of Wisconsin, Madison, WI, Other Publications October 15, 1982.

1. Marvin L. Cohen, "Calculations of Properties 8. Marvin L. Cohen, "Novel Superconducting of Materials," submitted to Encyclopedia of Materials and Mechanisms," invited closing paper, Material Science and Engineering. International Conference on Superconductivity in d- and f-Band Metals, Karlsruhe, Germany, June 30, 2. Marvin L. Cohen, "Semiconductor," Funk and 1982. Wagnall's Encyclopedia, in press. 9. Marvin L. Cohen, "Pseudopotential Total Energy 3. John E. Northrup and Marvin L. Cohen, Calculations for Si(lll)-(lxl) and Si(lll)-(2xl)," "Pseudopotential Total Energy Calculations for 16th International Conference on the Physics of Si(lll)-(lxl) and Si(lll)-(2xl)," The 16th Semiconductors, Montpellier, France, September 7, International Conference on the Physics of 1982. Semiconductors. Montpellier, France, in press. 10. Marvin L. Cohen, "Static and Structural Properties of III—V Zincblende Semiconductors," 4. S. Froyen and Marvin L. Cohen, "Static and 16th International Conference on the Physics of Structural Properties of III—V Zincblende Semiconductors, Montpellier, France, September Semiconductors," The 16th International 10, 1982. Conference on the Physics of Semiconductors, Montpellier, France, in press. 11. Marvin L. Cohen, "Predicting the Bulk and Surface Structure of Solids," Department of 5. Pui K. Lam and Marvin L. Cohen, "Calculation Chemistry, University of Hawaii, December 23, of High Pressure Phases of Al," in press. 1982. 97

7. Chemical Structure

a. Low-Temperature Properties of Material** Norman £ Phillips, Investigator

Introduction. This program contributes to an understanding of the properties of materials by providing experimental data, usually on low- •h3ased on LBL-13790 and LBL-M399. temperature specific heats, for comparison with models or microscopic theories. Specific heat 2. THE SPECIFIC HEAT OF 3He IN THE FERMI LIQUID measurements can be made under pressure and in high magnetic fields. Since the accuracy of heat REGION* capacity data is critically dependent on the accuracy of temperature measurements, the mainte M. C, Mayberry, E. W. Hornung, and Norman E. nance and improvement of a laboratory temperature Phillips scale for the region 1 mK to 30 K are important parts of the program. Because the interactions between $He atoms are the same as those that produce superfluidity in 4He but the statistics are the same as thosa 1. ABSOLUTE TEMPERATURE DETERMINATIONS IN THE mK of the conduction electrons in metallic super 1 REGION " conductors, the properties of liquid 3He provide a unique opportunity to test theories of many-body W. E. Fogle, E. W. Hornung, M. C. Mayberry, and systems in general and of superconductivity in Norman E. Phillips particular. The values of Fermi liquid parameters that can be derived from the Fermi liquid specific Thermometers that measure absolute temperatures heat are of fundamental importance to these tests, in the mK region are generally not useful as work but the specific heat data reported to date differ ing thermometers. For example, noise and nuclear by up to 40% in magnitude and have qualitatively orientation (NO) thermometers require long measur different temperature dependences. These differ ing times for good accuracy. In certain important ences have led to speculation that the data may applications cerium magnesium nitrate {CMN) sus include significant surface contributions that ceptibility thermometers are excellent working have not been characterized, but they have left thermometers but their accuracy i.* limited by the open the question of the bulk liquid specific uncertainty in A (=0 ± 1 mK) in the expression heat. for the susceptibility, x = const./(T - A). The value of A cannot be obtained with sufficient accuracy at temperatures above 2 K, where the The specific heat of liquid 3He has been absolute temperature has been relatively well remeasured between 12 and 160 mK using a CMN defined by classical methods, and it has been a thermometer {see preceding article). subject of controversy for over 10 years. The results are compared with other data in Fig. 2.1. At low temperatures the specific heat The value of A was determined by comparing a is proportional to T as expected for a Fermi 60Co in Co NO thermometer with several CMN ther mometers in the mK region. Values of temperature were derived from the -pray intensities in two directions, thus exploiting an infrequently used but important capability of the NO technique to provide an internal check on the accuracy of the results.

For several thermometers using stoichiometric CMN, A = 1.05 * 0.10 mK. Evidence was obtained that both excess water of hydration and an effect associated with superconducting coils and flux- trapping tubes can lower the value of A. The results have interesting implications for mK temperature measurements in general and for the properties of 3He in particular.

*This work was supported by the Oirector, Office Fig. 2.1. The specific heat of liquid ^Hez this of Energy Research, Office of Basic Energy Sci work, open circles; data from 3 other laboratories, ences, Materials Sciences Division of the U.S. solid curves {with error bars representing overall Department of Energy under Contract No. scatter); as recalculated on modified temperature DE-AC03-76SF0U098. scales, dashed curves. (XBL 831-3508) 98

liquid and gives a new value for the effective 4. OBSERVATION OF THE SPIN GLASS-PARAMAGNET mass that will be important in reanalyzing the PHASE BOUNDARY* superfluid properties. The figure also shows that plausible changes in the temperature scales W. E. Fogle, R. A. Fisher, and Norman E. Phillips in use in other laboratories reduce the discrep ancies to a\.out 5% and suggests that surface The nature of the transition from spin glass effects may not be important. The measurements to paramagnetic behavior is one of the more are being extended to lower temperatures. interesting and fundamental questions presentee by disordered materials. A recent extension of v* * * mean field theory to 3-dimensional spins leads to predictions that are qualitatively different from +Brief version of LBL-15646. those of earlier theories: The phase boundary in the H-T (field-temperature) plane should have an H2 dependence, and it should appear as a third 3. LOW-TEMPERATURE SPECIFIC HEAT OF POTASSIUM* order anomaly in the specific heat but not be detectable in the magnetic susceptibility. John Van Curen, E. W. Hornung, J. C. Usjaunias, and Norman E. Phillips Specific heat data on CuMn that had been taken for other purposes were analyzed for evidence of A number of unexpected properties of potassium the predicted anomaly. can be understood as charge-density-wave (CDW) effects. Direct proof that potassium, one of the Although the specific heat effects associated closest approximations to a free-electron metal, with ordering in spin glasses are much broader in has a CDW ground state would have far-reaching temperature than mean field theory predicts, there implications for the theory of metals. Such is a small anomaly with the predicted field and proof, in the form of an anomaly in the specific temperature dependence that is clearly separable heat, has been reported,! but it has been ques froiii the rest of the specific heat. This result tioned2 on the basis that the anomaly might supports the view that there is a real transition arise from temperature scale errors. in the thermodynamic sense, and constitutes a striking confirmation of the qualitative validity The recent work on the laboratory temperature of mean field theory. Similar measurements on scale ensures its accuracy in the relevant temper other spin glasses that might show a different ature region, and new specific heat measurements type of ordering are planned. were undertake" to provide a more rigorous test of the theoretical prediction. * * * *This result was included in an invited paper As shown iri Fig. 3.1, the measured heat presented at the International Conference on capacity has the form expected for the usual Magnetism, Kyoto, Japan, September 1982; to be lattice and electronic contributions. This result published in J. Magn. and Mag. Mat., LBL-14845. shews either that potassium does not have the sug gested CDW ground state or that the associated specific heat anomaly is an order of magnitude 1982 PUBLICATIONS AND REPORTS smaller than predicted. Similar measurements on other alkali metals are planned. Refereed Journals * * * 1. w. E. Fogle, E. W. Hornung, M, C. Mayberry, and Norman E. Phillips, "Experiments with tBrief version of Phys. Rev. Lett. 49, 1653 Powdered CMN Thermometers Between 10 mK and 4 K, (1982); LBL-15126. ~ and a Comparison with an NBS SRM 768 Fixed Point 1. C. D. Amarasekara and P. H. Keesom, Phys. Rev. Device," Physics 109 & HOB, 2129 (1982); Lett. 47, 1311 (1981). LBL-13790. 2. Norman E. Phillips, Phys. Rev. Lett. 48, 1504 (1982); A. H. MacDonald and Roger Taylor,"Toid., 2. William E. Fogle, James D. Boyer, Norman E. 1505 (1982). Phillips, and John Van Curen, "Fogle et al. Respond," Phys. Rev. Lett. 49, 241 (1982); LBL-14741.

3. Norman E. Phillips, "Phason Anomalies in Alkali Metal," Phys. Rev. Lett. 48, 1504 (1982); LBL-13791. 4. John van Curen, E. W. Hornung, J. C. Lasjaunias, and Norman E. Phillips, "Absence of Phason Contribution in the Specific Heat of Potassium," Phys. Rev. Lett. 49, 1653 (1982),- LB1-15126.

LBL Reports Fig. 3.1. Deviations of the specific heat of potassium from a least squares fit to the usual 1. William E. Fogle, "Some Experiments in low-temperature expression. (XBL 831-3506) Low-Temperature Thermometry," LB1-14399, 99

Invited Talks Kyoto, Japan, September 1982, LE1-14845.

1. G. E. 8rodale, R. A. Fisher, W. E. Fogle, 2. Norman E. Phillips, "Calorimetric Studies of N. E. Phillips, and J. Van Curen, "The Effect of Spin-Glass Ordering in CuHn," Department of Spin-Glass Ordering on the Specific Heat of Physics, Hokkaido University, Sapporo, Japan, CuMn," International Conference on Magnetism, September 16, 1982. 32

2. WORK IN PROGRESS Acid Electrolytes," J. Electrochem. Soc. 129, 567 (1982). (With P. K. Andersen and R. H. Muller) 7. C. W. Tobias, F. R. McLarnon, and R. H. Boundary 7ayer thinning by means of suspended Muller, "Interferometric Study of Combined Forced inert solids in the electrolyte moving past the and Natural Convection," J. Electrochem. Soc. electrode surface is measured using a rotating 129. 2201 (1982); LBL-13032. disk electrode. Following earlier work on spher ical glass beads in this laboratory, optimal par 8. C. U. Tobias and P. J. Sides, "Resistance of ticle shapes and sizes are being evaluated for a Planar Array of Spheres, Gas Bubbles on an other inert materials. The incremental viscous Electrode," J. Electrochem. Soc. 129, 2715 energy dissipation caused by the presence of (1982); LBL-13468. suspended particles is also to be deters.ned.

(With D. Fischl and !?. H. Muller) Other Publications

The effect of fixed flow obstacles on enhancing *1. C. W. Tobias and P. C. Foller, Inventors, mass transfer rates to and from planar electrodes "Electrolytic Process for the Production of in a channel is measured by the limiting current Ozone," U. S. Patent No. 4,316,782, February 23, method, and results are compared to rates evalu 1982. ated by the interferometric technique. The incre mental power requirement caused by the presence 2. C. W. Tobias, Chairman, "Assessment of of flow obstacles will be measured and then cor Research Needs for Advanced 8attery Systems," related with the improvement in mass transport Report of the Committee on Battery Materials rates. Technology, National Materials Advisory Board, Commission on Engineering and Technical Systems, (With D. Barkey and R. H. Muller) National Research Council, Publication NMAB-390, 1982. High speed electrofcrming is investigated as an inverse process to high speed anodic dissolu +3. C. W. Tobias and A. Kindler, "The Morphology tion. Our Hanson Van Winkle Munning ECM apparatus of Electrodeposited Copper," Extended Abstracts, is being modified to accommodate rapid forming of The 161st Meeting of the Electrochemical Society, a suitable test shape by deposition of copper. Montreal, Canada, May 9-14, 1982. Initial efforts are directed to identifying suit able mass transport conditions to attain high 4. C. W. Tobias, R. H. Muller, and D. J. Roha, current densities (10-100 A/cm) and to determine "Effect of Suspended Particles on the Rate of possible kinetic limitations of electroc:'ystalli- Mass Transfer to a Rotating Disk Electrode," zation associated with high deposition rates and Extended Abstracts, The 161st Meeting of the their effect on micromorphology and stress in the Electrochemical Society, Montreal, Canada, May deposit. 9-14, 1982.

+5. C. W. Tobias and Dennis Dees, "A Micro-Mosaic 1982 PUBLICATIONS AND REPORTS Electrode for the Study of Transport Phenomena at Gas Evolving Surfaces," Extended Abstracts No. Refereed Journals II-C-19, Vol. I, p. 468, 33rd Meeting of the International Society of Electrochemistry, Lyon, +1. C. W. Tobias and G. A. Prentice, "A Survey of France, September 10-15, 1982. Numerical Methods and Solutions for Current Dis tribution Problems," J. Electrochem. Soc. 129, 72 Invited Talks (1982); L8L-12191. 1. C. W. Tobias, "Mass Transport and Current 2. C. W. Tobias and G. A. Prentice, "Simulation Distribution in the Electrodeposition of Metals," of Changing Electrode Profiles," J. Electrochem. IBM Corporation, GTD Laboratory, Endicott, M. J., Soc. 129, 78 (1982); LBL-12192. January 22, 1982.

+3. C. W. Tobias and G. A. Prentice, "Deposition 2. C. W. Tobias, Diamond Shamrock Le,cures: "A and Dissolution on Sinusoidal Electrodes," J. Perspective of Electrochemical Technology," Electrochem. Soc. 129, 316 (1982); LBL-12167. January 25, 1982; "Current Distribution on Elec trode Surfaces," January 27, 1982; "Mass Transport *4. C. W. Tobias and G. A. Prentice, "Finite in Electrochemical Cell Processes," January 29, D-fference Calculation of Current Distributions 1982; "Physical Processes in Electrolytic Gas at Polarized Electrodes," AICHE. 28, 486 (1982); Evolution," February 1, 1982, Case Western L8L-11058. University, Cleveland, Ohio.

*5. C. W. Tobias and P. C. Foller, "The Anodic 3. C. W. Tobias, "Advances in Electrochemical Evolution of Ozone," J. Electrochem. Soc. 129, Technology," Seminar Lecture given at RCA Sarnoff 506 (1982). Research Center, Princeton, N. J., March 9, 1982.

*6. C. W. Tobias and P. C. Foller, "The Mechanism 4. C. W. Tobias, "Assessment of the Future of the Disintegration of Lead Dioxide Anodes Potential of Fuel Cells," Chevron Research Corp., under Conditions of Ozone Evolution in Strong Richmond, CA, April 16, 1982. m 5. C. W. Tobias, "Problems in Electrochemical 10. C. W. Tobias, "Prospects of Electrochemical Engineering," Seminar Lecture given at the Technology," Seminar lecture, Swiss Federal University of West Virginia, April 19, 1982. Institute of Technology, Lausanne, Switzerland, September 22, 1982. 6. C. W. Tobias. R. H. Muller, and D. J. Roha, "Effect of Suspended Particles on the Rate of 11. C. W, Tobias, "A Close Look at Electrolytic Mass Transport to a Rotating Disk Electrode," The Gas Evolution," Seminar lecture, Stanford 161st Meeting of the Electrochemical Society, University, February 24, 1982 and Ecole Rationale Montreal, Canada, May 14-19, 1982. Superieure des industries Chimiques, Nancy, France, October 21, 1982. 7. C. W. Tobias and A. Kindler, "The Morphology of Electrodeposited Copper," The 161st Meeting of 12. C. W. Tobias, "Perspectives on Electrochemi the Electrochemical Society, Montreal, Canada, cal Technology," Seminar )ec+'jrey De Guigne Tech May 14-19, 1982. nical Center, Stauffer Chemical Co., Richmond, CA and Laboratoire d'Electi ,-himie Interfacial» du 8. C. H. Tobias and Dennis Dees, "A Micro-mosaic C.N.R.S. Meudon (Bellevue) France, October i4, Electrode for the Study of Transport Phenomena at 1982. Gas Evolving Electrodes," The 33rd Meeting of the International Society of Electrochemistry, Lyon, * * * France, September 6-1C, 1982. ^Supported by the Division of Electrochemical 9. C. W. Tobias, "Fundamentals of Electrochemical Systems Research, Office of Conservation and Engineering," Six lectures arranged by the Romande Renewable Energy, U. S. Department of Energy. Intercantonal Association of Swiss Universities, 'Supported entirely from University funds. Leysin, Switzerland, September 12-16, 1982. 103 8. High Temperature and Surface Chemistry

a. High Temperature Thermodynamics* Leo Brewer, investigator

Introduction. High temperature chemistry is 1. USE OF GASEOUS-CONDENSED PHASE EQUILIBRATION characterized by the occurrence of unusual species TO DETERMINE THERMODYNAMIC QUANTITIES FOR VERY and phases that are often unstable at conventional STABLE TRANSITION METAL ALLOYS* temperatures. Because of the difficulty of carrying out measurements under conditions where it is Leo Brewer and John Gibson often difficult to contain the materials and to avoid contamination, it is important to design ex A transition metal nitride, MN, in equilibrium periments to yield information that can be used with a fixed nitrogen pressure, P^, provides a with predictive models. In this manner, one can source of the transition metal at a known thermo often calculate chemical behavior under conditions dynamic activity, am. Several of the platinum where measurements have not been made or would not group metals, P, have been equilibrated with be practical. various nitrides of the group IV and V transition metals at temperatures exceeding 2000*C, and the In the past, our research has aimed mostly at composition of the resulting alloys, MxPj_x, has improving our understanding of the behavior of been determined by electron microprobe analysis. gases at high temperatures and of refractory con It has been possible to study a range of alloy tainment materials. At present, our main thrust compositions for each binary combination by vary is aimed at improving our understanding of the ing PN from 0.1 to 11 atm in a graphite tube re thermodynamics of metallic alloys. For many al sistance furnace, but the available compositions loys, we have a good understanding of the inter have been rather limited because of rapid varia actions and have quantitative-predictive models tions in a with x for these strongly interact which allow predirtion of the behavior of unstud m m ied alloys. As an example, we have published a ing alloys. The results of these experiments have tabulation of the thermodynamic properties and been checked by a similar method involving equi phase diagrams of one hundred binary systems of libration with the corresponding carbide, MC, in molybdeni'-,.. However, there are some systems for the presence of graphite, but only a single a^ which our understanding is not adequate to allow and thus a single alloy composition is accessible such quantitative predictions. Our research is by this method. aimed at such systems. To study a wider range of alloys, the equilib Although we will report on other studies, our rium vapor pressures of one or both components main thrust at present is to characterize the very over alloys of known composition have been deter stable intermetallic compounds that result from mined for several binary combinations. The inten the reaction of transition metals from the left- sity of atomic effusion from a Knudsen cell is de hand side of the Periodic Table, which do not have termined by either mass spectrometry or gravimet- enough electrons to use all of their bonding orb- ry, and the effusion rate is converted into the itals, with transition metals from the right-hand partial pressure of the component(s) monitored. side, which have so many valence electrons that It was hoped to be able to determine the atomic they are paired in nonbonding orbitals. Our earl intensity of both constituents in the effusate ier studies have demonstrated the vigor of such from the several Nb-Pd alloys studied with a high reactions and the unusual properties of the re temperature mass spectrometer made available by sulting phases. It has been difficult to find re Professor Karl Gingerich of Texas A & M Univer liable methods of determining the thermodynamic sity, but even this very sensitive instrument properties of these phases. Ordinary calorimetric could not accurately measure the pressure of the methods are unusable because of the insolubility more refractory component, Nb, of these tightly of the phases. A variety of other techniques have bound alloys at the highest operating temperature been considered. Each has posed severe experimen of 2300'C. In the case where one constituent is tal problems under the conditions that must be much more volatile than the other, the weight loss used. The several methor.s being used will be de from a Knudsen cell in high vacuum at high temper scribed below. ature may be simply related to the vapor pressure of the more volatile component, and gravimetric experiments have been used to determine the Pd va por pressure over Zr-Pd, Hf-Pd, Nb-Pd, and Ta-Pd alloys. Preparations are under way to measure the vapor pressure of Ti over Ti-Ir and Ti-Pt alloys using this method. *This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sci * * * ences, Materials Sciences Division of the U.S. Department of Energy under Contract No. TSee LBL-13466 and LBL-10633 for details of meth DE-AC03-76SF00098. ods used. 104

2. HIGH TEMPERATURE EMF MEASUREMENTS* 1"3. G. M. Rosenblatt, "Use of Pitzer's Equations to Estimate Strong-Electrolyte Activity Coeffi Leo Brewer and Michael Cima cients in Aqueous Flue Gas Desulfurization Proc esses," American Chemical Sociity Symposium Ser Wagner solid state celts offer the possibility ies, No. 188, Flue Gas Desulfurization, edited by of determining relative partial molar Gibbs Ener J. L Hudson and G. T, Rochelle, p. 57-73 (1982). gies of Engel alloys over a wide composition range. Important systematic errors may result from impur + 4. B. Meyer, M. Rigdon, T. Burmer, M. Ospina, ities in the electrolyte., side reactions at the K. Hard, and K. Koshlap, "Thermal Decomposition electrode-electrolyte interface, and oxygen trans of Sulfite, Bisulfite, and Disulfite Solutions," port through pores in the electrolyte. The high American Chemical Society Symposium Series No. stability of yttria-doped thoria reduces the 188, Flue Gas Desulfurization, edited by J. L. chance of reactions, but it is difficult to pro Hudson and G. T. Rochelle, p. 113-125 (1982). duce in high purity, dense ceramic bodies. VJe have used an oxalate coprecipitation method to make starting material of extremely small LBL Reports particle size. Suitable equipment has been constructed to fire compacts of these powders in "U. B. Meyer, K. Koshlap, K. L. Geisling, and the presence of hydrogen at temperatures in R. R. Miksch, "Comparison of Wet and Dry Test excess of 2100°C. The product's pore structure Methods for Formaldehyde Emission from UF-Bonded is closed, and can therefore be used in cell Wood Products," to be published in Forest Products construction. J., IBL-14259. The first alloy to be studied by the EMF tech T2. B. Meyer and N. Carlson, "Formaldehyde Emis nique will be the Nb-Pd system through the cell sion from Particleboard Postcurved by Radiofre-

Pt/Nb-Pd alloy, Nb02/ThO2(YOx.5)o.i5/Nb02, quency Heating," to be published in Holzforschung, NozQ^gQ/Pt. Currently, we are preparing elec LBL-14Z86. trodes of niobium oxide, the "Lewis acid." They must be well characterized before use in the cell +3. B. Meyer, M. Rigdon, and K. Koshlap, "Raman to ensure that they are in equilibrium. and C-13 WR Spectrometric Study of the Reaction * * * of Sulfite and Formaldehyde," LBL-12452. 'See LBL-7691 for discussion of general method. 4. L. Brewer, "Systematics of the Properties of the LantSanides," presented at NATO Advanced Study Institute on the Lanthanides at Braunlage, Ger 1982 PUBLICATIONS AND REPORTS many, July 11-25, 1982, to be published in NATO Proceedings, LBL-14811. Refereed Journals 5. L. Brewer, "The Generalized Lewis-Acid-Base 1. M. Salmeron, L. Brewer, and G. A. Somorjai, Theory: Surprising Recent Developments," pre "The Structure ariu Stability of Surface Platinum sented at American Chemical Society G. N. Lewis Oxide and Oxides of Other Noble Metals," Surf. Symposium at Las Vegas, NV, March 30, 1982, to be Sci. 112, 207 (1981); L8L-12411. published in ACS Symposium Proceedings, LBL-14867. i

i"2. L. Peter and B. Meyer, "The Structure of the 6. L. Brewer, "Mathematical Representation of Dithionite Ion," J. Mol. Struc. 95, 131 (1982); Size and Electronic Factors," presented at Mater LBL-13783. ~~ ials Research Society Annual Meeting at Boston, MA, November 2, 1982, to be published in Proceed +3. B. Meyer and M. Ospina, "Raman Spectrometric ings, LBL-15220. Study of the Thermal Decomposition of Aqueous Tri- and Tetrathionate," Phosphorus and Sulfur 14, 7. L. Brewer, "HP-41C Calculator Programs for Z3-36 (1982); LBL-14440. "~~ Fitting of Data by Analytical Functions," LBL-15346.

Other Publications Invited Talks 1. L. Brewer, Bibliography on the_ High-Tempera ture Chemistry and Physics of Materials, Vol.?6, 1. L. Brewer, "The Relationship Between Thermo Part 2, "Gases: (A) Spectroscopy of Interest to dynamics find Phase Oiagrams," CALPHAO XI Confer High-Temperature Chemistry, and (B) Reactions Be ence, Argonne National Laboratory, May 17, 1982. tween Gases and Condensed Phases," edited by M. G. Hocking and V. Vasantasree, published by 1UPAC 2. L. Brewer, "Generalized Lewis Acid-Base Inter Commission on High Temperatures and Refractory actions in Metallic Systems," San Francisco Bay Materials, London, 1982. Area High Temperature Conference, Stanford Uni versity, Stanford, CA, May 19, 1982. +2. L. Brewer, "Thermodynamic Values for Desul- furization Processes," American Chemical Society 3. L. Brewer, "The Role of Electronic Configura Symposium Series, No. 183, Flue Gas Pesulftiriza- tions in Transition Metal Solid-Liquid Equilbria," tion, edited by J. L. Hudson and G.'T". Rochelle, workshop on Alloy Theory, Lo" Alamos National pTT-39 (1982); LBL-13846. Laboratory, Los Alamos, Wi, Sept. 9, 1982. 105

4. L. Brewer and D. G. Davis, "Predictions of the tThis work was supported by the Assistant Secre Engel Theory of Metallic Bonding, Resolution of a tary for Fossil Energy, Office of Coal Research, Contradiction," Pacific Conference on Chemistry Advanced Environmental control Division of the and Spectroscopy, San Francisco, CA, Oct. 27, U. 5. Department of Energy under.Contract No. 1982. DE-AC03-76SF0O098 through the Horgantown Energy * * * Technology Center, Morgantown, WV. 106

b. Chemistry and Materials Problemt In Energy Production Technologies* D. R, Olander, Investigator

1. THE l!02 - ZIRCALOY CHEMICAL INTERACTION"*" gram of Fig. 1.1. The kinptics of the process are governed by diffusion of oxygen and uranium D. R. Olander in *:he five-zone system with chemical equilibrium it four ir-terfaces. Three of the zones consist The chemical affinity of UOj and zirconium is of two elements; these are treated by convention of practical importance because it affects the al scaling theory. Transport of all three ele integrity of nuclear reactor fuel elements in a ments (Zr, U, and 0} occurs in the remaining two severe core damage accident. The laboratory zones, one of which consists of two coexisting tests reported by Hofmann and Politis* revealed phases. Modeling of the system predicts product the complexity of the UO2 - Zircaloy inter layer growth rates which are in good agreement action, in which three corrosion layers develop with the experimental results at 1500*C, the only between the terminal phases. One of the layers temperature at which both kinetic and thermo is two-phase, which can only occur in a ternary dynamic information is available. system.

Existing experimental data on the interaction* have been analyzed with a model that accounts for "iBrief version of LBL-14353, to be published in the formation and growth of the three corrosion J. Nucl. Mater. layers between the oxide and the metal. The dif 1. P. Hofmann and C. Politis, J. Nucl. Meter. fusion path beginning at UO2 and ending at pure 87, 375 (1979). IT is shown as the heavy line on the phase dia-

uo2.Z5v

Mg. 1.1. The U-Zr-0 phase diagram at 1500° (Ref. 1) showing the diffusion path followed by the corrosion process. (XBL 824-5578)

2. INVESTIGATION OF IRON-CHLORINE REACTION BY the iodine pressure follows from the law of mass MODULATED MOLECULAR BEAM MASS SPECTROMETRY* action for the reaction Cs(g) + 1(g) = Csl(g). This system supports therefore an iodine pressure M. Balooch, H. J. Siekhaus,* and D. R. Olander of ~10"i5 atm, still too small to promote SCC.

Metal-halogen reactions have many technological An SCC model proposed by Peehs2 envisages applications which warrant study of their mecha that n layer of Zrl{s) forms en the cladding in nisms by the techniques of modern surface chemis ner surface and establishes an equilibrium pres try. For example, the high volatility of metal sure of Zrl4 by the reaction: Zrl(s) + 31(g) * halides has long been exploited in halogen lamp Zrl4.(g). The pressure of the tetraiodide, ~10_1° design and in production of high purity metals. atm, drives Zrl4 diffusion down a crack to pro Similar reactions may play important roles in the mote SCC. However, the calculated diffusion flux water-splitting cycle for hydrogen production. of Zrfy is too small to explain the observed crack propagation rates. The reaction of :nlorine with polycrystalline iron has been studied by modulated molecular beam- A second thermodynamic model of Zircaloy SCC mass spectrometric methods in the temperature proposed by Gotzmannl assumes that the Csl/Cs rai:ne 300 - 1250 K at equivalent chlorine pres couple acts to transport iodine from the fuel sures from 2 x 10-5 to 3 x 10-4 Torr. Volatile surface to the crack tip in a manner analogous to FeClg is the only detectable reaction product; the transport of oxygen in the fuel by the CO2/CO its production rate increases rapidly with sur or H2O/H2 couples. In this model, iodine is face temperature and levels off at -1200 K. A transported as Csl from the outer fuel surface to frequency-independent, 45'C reaction-phase lag the tip of a growing crack in the cladding. At suggests that a solid-state diffusion process is the crack tip Csl is decomposed to deliver iodine an integral part of the mechanism. The reaction and the liberated cesium gas diffuses back to the is shown to be nonlinear with reject to chlorine fuel-cladding gap to pick up more iodine from the beam intensity. The maximum in the frequency- fuel surface. Iodine supply to the tip allows the phase data and the high frequency drop-off indi crack to advance and continually exposes fresh cate a branch process on the surface for the metal surface that acts as a sink for iodine production of FeClg. Studies of the chemical transported by Csl. But the rate at which this state of the surface by laser-simulated desorp- process can supply iodine is too low to sustain a tion and by ESCA revealed the presence of a thin propagating SCC crack. In all cases examined, thc- scale of a solid iron chlorine at the spot struck great stability of Csl prevents attainment of by the modulated beam. iodine pressures sufficiently high for the opera tion of mechanisms which are based on purely thermodynamic grounds. If iodine is responsible The reaction model involves dissociative for Zircaloy SCC, nonequilibrium mechanisms such chemisorption of chlorine on the surface of a as Csl radiolysis, or kinetic limitations to the thin scale of FeCl followed by reaction to pro formation of the equilibrium mixture of the ele duce FeClg which desorbs. Solution of adsorbed ments present in the fuel-cladding gap, must act chlorine into the scale and diffusion to the to bypass the thermodynamic constraints. scale-metal interface competes with the surface reaction. The molecular beam date substantiated this model and permitted determination of the * * * rate constants of the elementary steps. +Brief version of J. Nucl. Mater. 110, 343 (1982). * * * 1. 0. Gotzmann, J. Nucl. Mater. 1077185 (1982). 2. M. Peehs, W. Jung, H. Stehle.and" E. Steinberg, tTo be published in Trans. Faraday Soc. in IAEA Specialists Meeting on Pellet-Cladding JGeneral Chemistry Division, LLNL. Interaction in LWRs, Riso, Denmark, September 1980.

3. A THERMODYNAMIC ASSESSMENT OF IN-REACT0R IODINE SCC OF ZIRCALOYr 4. MULTIPH0T0N LASER IONIZATION MASS SPECTROMETRY OF Csl and 1+ D. R. Olander M. Balooch and D. R. Olander Recurring failures of the Zircaloy cladding of LWR fuel rods may be because of stress corrosion An important aspect of the behavior of fission cracking (SCC) by elemental iodine. However, products in nuclear reactor fuel elements is the since the fission yield of cesium exceeds that of chemistry of cesium and iodine. Although thermo iodine, Csl, not I or Ig, is the overwhelmingly dynamics predicts that essentially all of the favored iodine-containing species. Cesium iodide, iodine should be present as Csl, which is non however, does not cause SCC of Zircaloy. Possible volatile and chemically nonaggressive in the fuel, thermodynamic explanations that could resolve this there is indirect evidence that elemental iodine discrepancy were examined and tested for possible may be released from irradiated fuel. kinetic limitations. In the present study the multiphoton ionization Gotzmannl has suggested that formation of technique (MPI) with a tunable dye laser is used the ternary cesium-molybdenum-oxygen compound, as a means of selectively ionizing Csl and I. CS2M0O4, controls the cesium pressure in the fuel- Figure 4.1 depicts the apparatus. Molecular beams cladding gap. Csl exerts its vapor pressure, and of Csl and I are produced in separate Knudsen Fig, 4.1. System for molecular beam ionization by laser multiphoton absorption processes. {XBL 828-6353)

cells. The molecular beam is intercepted by a In the present work, the reactions of molecular pulse laser with 5 ns width, repetition rate of chlorine with liquid and solid indium, lead, and 10 Hz, and maximum output power of 10 mj In the tin were studied by modulated molecular beam mass wavelength range of interest (-3000 A). The out spectrometric methods. InCl, PbClg and SnClg were put of mass spectrometer is processed by a multi the only detectable volatile reaction products. channel analyzer. Their production rates increase abruptly at the melting point, the effect being most pronounced The results show that when combined with mass for indium. In a separate study using AES, the analysis, multiphoton ionization has the potential surface coverage of chlorine was determined as a of providing a more highly selective means than function of beam intensity and surface electron impact ionization for detecting Csl and temperature. I in a mixture of the two vapors. The I atoms can be detected in a mixture with a Csl/l ratio Molecular beam studies of the In/Clg system as large as -10 by operating at a wavelength of show that the reaction probability increases 3047 A, But low repetition rates, short pulse abruptly by an order of magnitude at the melting times, and low effective ionization volumes make point of indium. Auger analysis of the surface laser mass spectrometry less effective for meas shows a dramatic drop in chlorine concentration urement of minute quantities than of one species at the same temperature. The apparent reaction in another. probability approaches a limiting value of 0.16 at -600 K. This behavior indicates that the re action rate in this temperature region is limited solely by the Clg supply, which is controlled +To be published T.T J. Mass Spect. and Ion Phys. by the sticking probability of molecular chlorine on the surface. The beam intensity variation confirms that the reaction is first order with respect to chlorine beam intensity for both 5, THE KINETICS OF GAS/SOLID/LIQUID REACTIONS BY liquid and solid phases of indium. MODULATED MOLECULAR BEAM MASS SPECTROMETRY

H. Balooch, W. J. Siekhaus,f and D. R. Olander "'"General Chemistry Division, LLNL, Over the last decade, understanding of gas- solid reaction processes has been greatly enhanced by utilizing modulated molecular beam techniques 1982 PUBLICATIONS AND REr'ClRTS in conjunction with AES, LEED, and ESCA. On the other hand, gas-liqu1d reactions, which are im Refereed Journals portant in photoflash devices, propellant, steelmaking, high temperature flames, transpiration 1. D. R. Olander, A. J. Machiels, H. Balooch, cooling, passivation of liquid metal alloy sur S. K. Yagnik, "Thermal Gradient Migration of faces, and many other applied areas, are poorly Brine Inclusions in Synthetic Alkali Halide Sin understood. gle Crystals," J. Appl. Phys. 53, 669 (1982). 109

2. D. R. Olander, D. Sherman, and M. Balooch, 7. D. Bayen, "Fission Product Release from

"Retention and Release of Water by Sintered Irradiated U02," LBL-15222. Uranium Dioxide," J. Nucl. Mater. 107, 31 (1982).

3. D. R. Olander, "A Model of Brine Migration and Water Transport in Rock Salt Supporting a Invited Talks Temperature Gradient," Nucl. Techno!* 58, 256 1. 0. R. Olander, "Analysis of Steam Oxidation (1982). of Zircaloy Cladding in High Temperature Nuclear 4. D. R. Olander, "A Mechanistic Analysis of Reactor Transients," Thermal Fuels Behavior Ruthenium Transport in UO2," Nucl. Sci. Eng. Division Seminar, EG8G, Idaho, March 18, 1982. 82, 190 (1982). 2. D. R. Olander, "Materials Problems in Nuclear 5. D. R. Olander, "A Thermodynamic Assessment of Reactors," Energy & Environment Division, In-Reactor Iodine SCC of Zircaloy," J. Nucl. Lawrence Berkeley Laboratory, April 13, 1982. Mater. UO, 343 (1982). 3. D. R. Olander, "Chemical Aspects of Pellet- 6. F. Tehranian and D. R. Olander, "Extrapolation Cladding Interaction in Light Water Reactor Fuel of Low Temperature Vapor Pressure Data of Uranium Elements," National Meeting, American Nuclear Carbide to the Liquid Regions," High Temp. Sci. Society, Los Angeles, California, June 8, 1982. 15, 329 (1982). 4. D. R. Olander, "Zircaloy Reactions with Steam 7. D. R. Olander, "The Chemical Diffusivity of and with UO2,1' Gordon Research Conference on Oxygen in U02_ ," J. Nucl. Mater. 110, 352 x High Temperature Chemistry, Panel on Nuclear (1982). Reactor Accident Modeling and High Temperature Chemistry, Tilton, New Hampshire, July 1982. LBL Reports

1. C. H. Tsai and D. R. Olander, "Rapid Heating 5. C. H. Tsai, "Laser Vaporization of Uranium and Vaporization of Binary Solids by Absorbing Dioxide," Chemical Eng. Div., Argonne National Radiation—I Numerical Modeling of Heat and Mass Laboratory, Argonne, Illinois, January 11, 1982. Transfer," LBL-15124. 6. M. Balooch, "Molecular Beam Studies of 2. M. Balooch and D. R. Olander, "Multiphoton Metal-Halogen Reactions," Surface Science Semi Laser Ionization Mass Spectrometry of Cesium nar, Materials and Molecular Research Division, Iodide and Atomic Iodine," LBL-14989. Lawrence Berkeley Laboratory, April 15, 1982.

3. D. R. Olander, "The UO2 - Zircaloy Inter 7. D. R. Olander, Lecture series on "Nuclear action," LBL-14353. Materials and Uranium Enrichment," Chinese Nuclear Materials Society, Beijing and Chengdu, 4. M. Balooch and D. R. Olander, "Kinetic Study June - July 1982. of the Zirconium-Iodine Reaction by Modulated Molecular Beam Mass Spectrometry," LBL-14518. 8. D. R. Olander, "The UOp-Zircaloy Interaction," Pacific Conference on Chemistry and Spectroscopy, 5. 5. H. Shann and 0. R. Olander, "Stress Cor San Francisco, California, October 27, 1982. rosion Cracking of Zircaloy by Cadmium, Iodine, and Metal Iodides," LBL-13855. 9. 0. R. Olander, "Core Damage and Release of Volatile Fission Products During a Reactor 6. S. K. Yagnik, "Thermal Gradient Migration of Accident," U.C. Berkeley, Department of Nuclear Brine Inclusions in Salt Crystals," L8L-14752. Engineering Colloquium, September 27, 1982. c. Plasma Enhanced Deposition of Thin Films*

Dennis W. Hess, Investigator

Introduction. Thin films are used in a wide incorporation from the titanium tetrachloride spectrum of applications, including optical source gas generates improved short wavelength coatings, solar cells, and integrated circuits. photoresponse compared to thermally oxidized Each application requires films with precise films. Apparently such improvements result from properties, tailored for that purpose. Thus, the reduction of grain boundary and/or surface fundamental relationships between film properties recombination site densities. and the deposition techniques used for film for mation must be established.

Because of the high energy electrons present *8rief version of LBL-14994. in an rf glow discharge or plasma, chemical ^Present address: Bell Laboratories, Murray reactions, which normally require elevated tem Hill, NJ 07974. peratures (>500'C) to proceed at a measurable rate, can be carried out at room temperature. Further, because of ion and electron bombardment of film materials during deposition, materials 2. STRUCTURE AND PHOTOELECTROCHEMICAL PROPERTIES with unique chemical, electrical, and optical OF PLASMA-DEPOSITED IRON OXIDE FILMS properties can be synthesized. Christopher S. Blair and Dennis VI. Hess Studies on the plasma-enhanced deposition (PED) of transition metal oxides are described. Iron oxide films have been used widely in the X-ray diffraction, transmission electron micros fabrication of electronic devices. The specific copy, and photon-assisted electrolysis are used applications range from magnetic recording tape, to investigate materials properties as functions to magnetic bubble memories, to transparent pho of deposition parameters. tolithographic masks, to photoanodes for solar energy conversion. Plasma-enhanced deposition offers a method of controlling the structure and 1. PLASMA-DEPOSITED TITANIUM OXIDE PHOTOANODES1" properties of iron oxide films, so that particu lar properties can be obtained by variation of Larry M. Williams* and Dennis W. Hess deposition parameters.

The current demand for solar energy conversion Iron oxide films are deposited by igniting a and storage has kindled an interest in photoelec- glow discharge in a vapor of iron pentacarbonyl trochemical systems. Inexpensive materials that and oxygen. The photoelectrochemical and struc display high cell efficiencies and low anode cor tural properties of the film are then studied and rosion are needed. Plasma-enhanced deposition is compared to those of iron oxide films formed by a technique capable of film formation on virtually other techniques. any substrate material over a wide temperature range. Thus far, plasma-deposited iron oxide films show relatively low photocurrent efficiencies, in An rf glow discharge is ignited in a mixture agreement with literature reports of other iron of titanium tetrachloride and oxygen, and titanium oxide photoanodes. Optical absorption measure oxide films are deposited on titanium substrates. ments on the plasma-deposited films indicate that Titanium oxide films are also formed by thermal most of the incident radiation is absorbed within oxidation of titanium substrates. Comparison of the first 30 nm of the film. Therefore, surface the composition and the photoelectrochemical and recombination may be the determining factor in structural properties of the films allows the role the low current efficiencies observed. Iron of the plasma in the establishment of thin film oxide films deposited in the glow discharge show properties to be ascertained. preferred orientation and much improved photo electrochemical properties when the deposition Plasma-deposited titanium oxide photoanodes temperature reaches 500*C. At this temperature, have been fabricated with quantum efficiencies a balance seems to be reached between ion-bom higher than the thermally grown anode materials bardment induced defect creation and crystallite and comparable to those reported for single crys orientation effects, leading to improved photoan- tal rutile. The reason for such results appears ode efficiencies. to be the preferred orientation of the grains observed in plasma deposition. Further, chlorine

1982 PUBLICATIONS AND REPORTS

*This work was supported by the Director, Office Refereed Journals of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the fl. 0. K. Chu, C. C. Tang, and D. W. Hess, U. S. Department of Energy under Contract No. "Plasma-Enhanced Chemical Vapor Deposition of OE-AC03-76SF00098. Tungsten Films," Appl. Phys, Lett. 41, 75 (1982). Ill

Other Publications Invited Talks

1. D. A. Doane, D. B. Fraser, and D. W. Hess, 1. D. W. Hess, "Plasma-Enhanced Deposition of Eds., Proceedings of the Tutorial Symposium on Silicon and Silicon-Containing Films," ASTM Sym Semiconductor Technology. The Electrochemical posium on Silicon Processing, San Jose, Society, Inc., 1982. California, January 1982.

LBL Reports

1. L. M. Williams, "Structure and Photoelectro- * * * chemical Properties of Plasma Deposited Titanium ^Supported by the Array Research Office under Dioxide, LBL-14994. Contract No. DAAG-29-80-K-0086. 112

d. Electrochemical Phase Boundaries*

Rolf H. Mutter, Investigator

Introduction. The p1 rpose of this work is to ± 1 kcal/mole (95% confidence level) for both sub advance the understanding of boundary layers and strates. Statistical analysis of the present data thin films at electrochemical interfaces. New dot's not support a partial charge for the elec- optical techniques are developed and used for the trosorption bond. In agreement with the forma observation of electrode surfaces in liquid media. tion of a smooth monolayer, no increase in light scattering was observed during formation of the Research on high-rate electrodeposition and underpctential deposit. The initial stages of dissolution* conducted jointly with C. W. Tobias, bulk deposition occur on top of the underpoten- is described under "Electrochemical Processes." tial layer. The optical model for the bulk Applied research, "Surface Layers on Battery Ma deposit involves a porous layer consisting of met terials," supported by the Office of Advanced al and electrolyte. The optical properties of Conservation Technologies, DOE, is reported under this composite layer have been determined by mix "Electrochemical Energy Storage." ing the properties of the two media according to the Bruggeman theory.3 Upon anodic dissolution, bulk and underpotential deposits are removed se- . 1. NUCLEATION OF Pb ELECTRODEPOSITS ON Ag AND quentially, and the original optical properties CUT of the substrate are restored. Joseph C. i armer and Rolf H. Muller

An important factor in determining the proper "tBrief version of LBL-15458. ties of electrodeposited metals is the nature of 1. D. H. Kolb, in Advances in Electrochemistry the first layer from which the deposit grows. and Electrochemical Engineering, Vol. 11, This work was undertaken to determine the micro- edited by H. Gerischer, Wiley, New York, 1978. morphology of the initial stages of Pb deposition 2. H. J. Hathieu, D. E. McClure, and R. H. Muller, on Ag(lll) and Cu(lll) from the first atomic Rev. Sci. Instrum. 45, 798 (1974). layer, the underpotential deposit (UPD), to bulk 3. D. E. Aspnes and J."Tf. Theeten, Phys. Rev. B deposits of about 200 A thickness. Substrates _20, 3292 (1979). and deposit were chosen because of their ability to form underpotential deposits1 and their dif ferences in optical properties that make optical 2. EFFECT OF RHODAMINE-B ON Pb ELECTRODEPOSITION detection of small amounts of deposit possible. ON Ag and Cu "t

Simultaneous cyclic voltammetry, ellipsometry, Joseph C. Farmer and Rolf H. Muller and light scattering measurements were conducted. The potential was swept from +200 to -800 mV vs Surface active agents have long been used on Ag/AgCl at rates from 0.1 to 1.5 V/min. The el- an empirical basis to control the surface finish lipsometer was of the self-nulling type,2 oper in electrolytic metal deposition.1 The objec ated with a Xe arc lamp with a filter for 515 nm. tives of this study were to determine coverage For the light scattering measurements an Ar-ion and orientation of an adsorbed model substance laser, operated at 515 nm, was used. Optimum and its effect on overpotential and micromorphol- values of the deposit properties (UPD thickness ogy of a metal deposit, ranging in thickness from and optical constants, bulk deposit thickness and atomic coverage to about 1000 A. porosity) were determined by minimizing the sum- of-squares errors between ellipsometer measure Most of the experiments were conducted with ments and model predictions. The optical con Rhodamine-B chloride as inhibitor, lead as de stants of bulk Pb And substrates were measured posit, and copper as electrode substrate. These and fall within the range of values found in the materials show different optical properties over literature. the visible spectrum. The choice of Rhodamine-B resulted from screening studies with over 15 The optical model, which was successful in in laser dyes that were investigated because they terpreting the ellipsometer measurements of the are strongly light-absorbing and can therefore be underpotential deposit, involves the two-dimen detected in small amounts on the surface; they sional spreading of metallic islands of monolayer also adsorb strongly, are optically well-charac thickness. Coverage of the surface was derived terized, and are available in high purity. Rho fron, charge passed. The free energy of adsorption damine-B has been found here to result in a large derived for a Langmuir isotherm was found to be 7 (150 mV) increase in the overpotential for the Pb bulk deposit. Lead ions are discharged at poten tials where neither the specific adsorption of chloride ions nor hydrogen evolution occur. The principal experimental techniques used were cyclic voltammetry and ellipsometry with light of fixed *This work was supported by the Director, Office wavelength or spectrally scanned over the visible. of Energy Research, Office of Basic Energy Sci ences, Materials Sciences Division of the U. S. Department of Energy under Contract No. Dye adsorption -s found to result in the for DE-AC03-76SF00098. mation of an incomplete monolayer in underpoten- 113

tial deposition and a bulk deposit of very low serves as achromatic quarter-wave compensator. porosity that causes the spectral features of the The wavelength dependence of the Verdet coeff substrate to disappear while they are still visi icients for the Faraday-cell glass cores was ble with the same amount deposited without the determined experimentally. A minicomputer dye (Fig, 2.1). Rhadamine-B, as most inhibitors (LSI-11/02) is used to collect data from up to used in practice, is reduced at the electrode 8 channels, average multiple runs, establish dif prior to metal deposition, and with the low con ference spectra, and fit model parameters to mea centrations used here, its effect therefore dis surements. appears after the first potential cycle. Re- adsorption during a relaxation period at open * * * circuit causes the effects to return. Birefrin gence of the dye layer indicates that the species •ffirief version of LBL-15607. responsible for the increase in overpotential has 1. H. J. Mathieu, D. E. HcClure, and R. H. its optical transition moment oriented normal to Muller, Rev. Sci. Instrum. 45, 798 (J<>74}. the surface and is probably bonded as a cation. 2. D. E. Aspnes, Appl. 0pt~14, 1131 (1975). * * * 4. WORK IH PROGRESS +Brief version of LBL-15459. 1. J. A. Harrison and H. R. Thirsk, in Electro- Joseph C. Farmer, Michael Armstrong, J. Richard analytical Chemistry, Vol. 5, edited by A. J. Gyory, and Rolf H. Muller Bard, Dekker, New Yorfc, 1971. Opticf.l models are being developed for the interpretation of ellipsometer measurements of electrochemical submonolayers for which equiv alent-film models, which have been used success fully for adsorption from the vapcr phase,* are not applicable. Anisotropic film models, in which the effect of molecular orientation is considered, are used for determining thickness and orientation of adsorbed dye layers.

Depth-profiling Auger spectroscopy is being combined with ellipsometry to provide additional experimental evidence for the interpretation of thin-film structures and compositions. Lead de posits on copper are investigated in support of studies reported above. Of particular interest is the possible incorporation of the reduced dye in the metal. Vapor-deposited model structures ABB see see 700 will be used to test optical interpretations. WAVELENGTHCNMi Some aqueous electrolytes of interest for use Fig. 2.1. Spectroscopic measurement of the el- in gas electrodes have been found in previous lipsometer parameter delta for a bare Cu sub work,2*^ to form stable liquid films on planar strate and Pb deposits formed with and without 2 vertical metal surfaces. A study has been init Rhodamine-B. Deposit 33 mC/cm , corresponds to iated to identify the forces responsible for film 31 nm compact layer. (XBL 828-11272A) formation. Present experimental efforts are con cerned with the preparation of solutions free of solid particulate impurities. 3. SELF-COMPENSATrNG SPECTROSCROPIC ELLIPSOMETER^ * * * Joseph C. Farmer and Rolf H. Muller 1. G. A. Bootsma, Surf. Sci. 14, 52 (1969). Spectral scanning adds another dimension to 2. J. H. Turney, LBL-171 (197T7. the ellipsometry of surfaces and thin films. Ex 3. H. Gu, LBL-165 (1971). tensive modification of a previously built self- compensating instrument* has made it possible to combine the advantages of rapid spectral 1982 PUBLICATIONS AND REPORTS scantling with the inherent accuracy2 of a compensating ellipsometer operated in the po Refereed Journals larizer-compensator-sample-analyzer confiyura- i -n. 1. F. R McLarnon, R. H. Muller, and C. W. Tobias, "Interferometric Study of Combined Forces A high-pressure xenon arc lamp serves as a and Natural Convection," J. Electrochem. Soc. white light source; wavelength can be varied con 129, 2201 (1982); LBL-13032. tinuously over the visible-uv (370 to 720 nm) at a maximum rate of 114 nm/s by rotating a continu 2. W. J. Plieth, "Electrochemical Properties of ously variable interference filter. A three-re Small Clusters of Metal Atoms and Their Role in flection Fresnel rhomb with extremely low skew Surface-Enhanced Raman Scattering," J. Phys. (<0.01 deg) between entrance and exit beams Chem. 86, 3166 (1982). 114

LBL Reports cleation of Pb Electrodeposition of Ag and Cu," L8L-15458 Abstract. 1. C. Coughanowr, "Electrochemical Machining of Cemented Titanium Carbide," M.S. thesis, Other Publications LBL-13682. 1. R. H. Muller, D. J. Roha, and C. W. Tobias, 2. Joseph C. Farmer and Rolf H. Muller, "Effect "Effect of Suspended Particles on the Rate of of Rhodamine-B on Pb Electrodeposition on Ag and Mass Transfer to a Rotating Disk Electrode," Pro Cu," LBL-15459 Abstract. ceedings of the Symposium on Transport Processes in Electrochemical Systems, Voi. 82-10, Electro 3. Joseph C. Farmer and Rolf H. Muller, "Nu- chemical Society, 1982. 715

e. Solid State and Surface Reactions* GaborA. Somorjai, investigator

Introduction. The research program is 2. EVIDENCE FOR THE FORMATION OF STABLE centered on studies of catalyzed surface reac ALKYLIDYNE STRUCTURES FROM C3 AND C4 UNSATURATED tions and investigations of the atomic structure HYDROCARBONS ADSORBED ON THE Pt{lll) SINGLE and chemical composition of solid surfaces and CRYSTAL SURFACE^ adsorbed monolayers. The kinetics and mechanisms of catalytic surface reactions are studied using R. J. Koestner, J. C. Frost, P. C. Stair, M. A. well-characterized crystal surfaces at low and Van Hove, and G. A. Somorjai high pressures by using a combination of surface science techniques. C3 and C4 hydrocarbon (methylacetylene, propylene, and the 2-butenes) adsorption on the The materials that are the focus of our Pt(lll) face was studied by observing the LEED studies are platinum, molybdenum, rhodium, iron patterns that formed and by measuring the inten and its compounds, alkali metals, and bimetallic sity vs voltage spectra for each structure. Two alloys. The adsorbates and reactants are mostly phases exist for each of these molecules adsorbed hydrocarbons, oxygen, hydrogen and water. on the Pt(lll) surface. At low temperatures, the unsaturated C-C group forms a di-alkynes, ture and catalytic behavior of metal surfaces. a conversion takes place to an alkylidyne species The other part is aimed at developing new cata that is bonded to three Pt atoms and has its C-C lysts which substitute for precious metals and bond nearest to the metal substrate oriented per exhibit high rates and selectivity. pendicularly to t!*e surface. The butyl idyne spe cies is shown to order its ethyl group into an (8 x 8) or [Z/5 x 2/3)R30" superlattice, when the Surface Structure and Chemisorption by Low Energy hydrocarbon exposure is increased; this ordering Electron Diffraction and Electron Spectroscopy is probably a natural consequence of the steric hindrance among neighboring ethyl groups as the hydrocarbon coverage increases slightly with larger exposures. 1. A LEED CRYSTALLOGRAPHY STUDY OF THE

(2x2)-C2H3 STRUCTURE OBTAINED AFTER ETHYLENE ADSORPTION ON Rh(lll)"1" # * *

R. J. Koestner, M. A. Van Hove, and G. A. Somorjai +Brief version of LBL-12780.

The structure of the Rh(lll)-(2x2)-C2H3 overlayer that was obtained upon the adsorption 3. FORCE-FIELD CALCULATIONS OF THE PACKING of ethylene has been determined using a LEED ENERGY OF MONOLAYERS OF C3 AND C4 HYDROCARBON intensity analysis. In agreement with a prior MOLECULES ADSORBED ON SINGLE" CRYSTAL METAL HREELS study, an ethylidyne (= CCH3) sppcies is SURFACES''' found to stand perpendicularly above an hep hol low site with a carbon-carbon distance of 1.45 * A. Gavezzotti, M. Simonetta, M. A. Van Hove, and 0.10 A and a metal-carbon distance of 2.03 ± G. A. Somorjai 0.07 A. The Zanazzi-Jona and Pendry R-factors for this structure are 0.49 and 0.52, respective Force-field calculations have been applied to ly. By comparison with similar organometallic investigate the packing energy of overlayers of complexes, the relatively short carbon-carbon C3 and C4 hydrocarbons adsorbed on Pt(lll) and distance and long metal-carbon distance can be Rh(lll), in which Van der Waals adsorbate- explained by 0 - n hyperconjugation of the sur adsorbate interactions play a significant role. face ethylidyne fragment. The packing energies were used to conpare various adsorbate structures for which Low Energy Elec tron Diffraction patterns have been obtained and corresponding detailed structures have been pro Vief version of LBL-13598, LBL-13962, LBL-12803, posed. In particular, the conformation of methyl- and LBL-13300. acetylene (HCCCH3) in a (2 x 2) arrangement,

and of propylidyne (2CCH2CH3) and butylidyne found to be perpendicular to the surface in a 3-

(=CCH2CH2CH3) in (2 x 2), c(4 x 2) and (2/3 x fold hollow site in agreement with experimental 2»^)R30" arrangements were considered. observations. It is also found that a displace ment of C-CH2-R to a top site makes a C-R cleav * * * age easier.

"^Brief version of LBL-14053. * * * +Brief version of LBL-13603. 4. VIBRATIONAL STUDIES OF ALKENE DECOMPOSITION ON THE Rh(lll) SURFACE 6. THE ADSORPTION OF BENZENE AND NAPHTHALENE ON B. E. Koel, J. E. Crowell, M. Mate, and G. A. THE Rh(lll) SURFACE: A LEED, AES, AND TDS STUDYt Soinorjai R. F. Lin* R. J. Koestner, M. A. Van Hove, and The identification of the hydrocarbon surface G. A. Somorjai species that can form on the Rh surface as a function of temperature has important mechanistic The adsorption of benzene and naphthalene on implications for catalytic methanation and the Rh(lll) single-crystal surface has been Fischer-Tropsch synthesis reactions. Data are studied by low energy electron diffraction (LEED), also needed on the bonding and rehybridization of Auger electron spectroscopy (AES), and thermal these species to determine the importance of »-d desorption spectroscopy (TDS). Both benzene and bonding in adsorption and catalytic reactions on naphthalene form two different ordered LEED group-VIII metals. patterns separated by temperature-induced phase transitions: (J-J) - c(2*ff x 4)rect and (3 x 3) High resolution electron energy loss spectros copy (HREELS) has been used to study the struc for benzene, (3/T x 3*3)R30", and (3 x 3) for ture of the hydrocarbon monolayers formed under naphthalene, with increasing temperature, the ultrahigh vacuum conditions from the dissociative patterns are found to disorder near or below the adsorption of ethylene, propylene, and butenes on first hydrogen TDS peaks. All these phase transi the Rh(lll) surface above 300 K. The HREELS tions are irreversible. The ordered structure spectra obtained between 300-430 K indicate the can be understood in terms of flat-lying or near formation of stable alkylidyne species, as sug ly flat-lying intact molecules, and they can be gested by previous LEED studies. compared with similar structures found on other metal surfaces. Structural models and phase Similarities in the temperature dependence of transition mechanisms have been proposed. the sequential dehydrogenation of the surface species can be found. For example, above 430 K * * * only a single high intensity vibrational mode is observed near 780 cm-*, indicating the partially +Brief version of LBL-15820. dehydrogenated-surface species is primarily ab sorbed methylidyne (CH/a)) in all cases. Heating to 800 K in UHV is sufficient to remove all sur 7. VIBRATIONAL SPECTROSCOPY USING HREELS OF face hydrogen in all cases. The carbonaceous 8ENZENE ADSORBED ON THE Rh(lll) CRYSTAL SURFACE layer formed gives only weak loss peaks and no clearly identifiable Rh-C or C-C vibrational B. E. Koel and G. A. Somorjai modes. High resolution electron energy loss spectros copy (HREELS) and low energy electron diffraction (LEED) have been used to study the structure of 5. A COVALENT MODEL FOR THE BONDING OF ADSORBED adsorbed benzene (C5H5 and C5D6) monolayers on HYDROCARBON FRAGMENTS ON THE (111) FACE OF the Rh(lll) surface at 300 K. Benzene is associ- PLATINUMt atively adsorbed and -r-bonded to the surface with the ring plane parallel to the surface plane. C. Minot, M. A. Van Hove, and G. A. Somorjai The adsorption of benzene on Rh(llX) is similar to that on Pt(lll) and Ni(lll) surfaces, giving A systematic molecular orbital study of the rise to similar HREELS spectra, except that only one type of adsorption site is present on Rh(lll), location of CHn and C-CHn (n = 1,2,3) species on a Pt(lll) single-crystal surface has been performed indicated by a single symmetric C-H out-of-plane by using an Extended Huckel Theory (EHT). These bending vibration. species may be involved in the hydrogenation/ dehydrogenation processes of hydrocarbons. The A C(2v3"x 4) structure is formed after large observed dependence of the adsorption site on the exposures. HREELS gives information on the sur number of hydrogens in the CHn fragments sug face bonding geometry thv. is complementary to gests that any CH bond breaking in CHn species the LEED data, providing good description of the must involve a change of adsorbate bonding site. adsorbed monolayer. For this ordered structure, The carbon is found to be located on the surface the symmetry of the benzene molecules is only in such a way as to complete its tetravalency. weakly distorted from Cgv to C3V(og-) symmetry, and Thus, CH occupies a 3-fold coordinated hollow the adsorption site is probably the on-top site site, CH2 a 2-fold coordinated bridge site, and with the benzene ring centered over a single Rh CH3 a 1-fold coordinated top site. C-CH3 is atom. 117

8. THE STRUCTURE OF GRAPHITIC CARBON ON PT(lll) are because of molecular CO adsorption with a sub stantial charge donation from potassium through D. F. Ogletree and G. A. Somorjai the platinum substrate and into the 2 •** CO orbital. When carbon is deposited on the Pt(lll) surface by dehydrogenation of hydrocarbons, it * * * forms a disordered overlayer of carbidic carbon. Annealing at 750-800 K produces diffraction rings *Brief version of LBL-13349 and LBL-14335. that correspond to the lattice spacings in the basal plane of bulk graphite. These rings are due to islands of graphite-like carbon at random 10. THE INTERACTION OF POTASSIUM WITH ^-ELECTRON orientations relative to the platinum substrate. ORBITAL CONTAINING MOLECULES ON Pt(lll)i" Further annealing at 1050-1100 K causes the graph ite diffraction rings to segment into elongated E. L. Garfunkel, J. J. Maj, M. H. Farias, J. C. spots. These spots indicate domains of graphite Frost, and G. A. Somorjai like carbon rotated by 23 and 37 degrees relative to the platinum substrate. The elongation of the The interaction of co-adsorbed potassium with spots in the angular direction, about three times T-orbital containing molecular adsorbates the width in the radial direction, suggests a (benzene, PF3, N0y CaHg, and CH3CN} on the distribution of four to six degrees in the angu Pt(lll) crystal surface was studied by thermal lar registry between the islands of the incommen surate graphite-like lattice and the substrate desorption spectroscopy. Co-adsorbed potassium lattice. significantly weakened the platinum-benzene bond. Upon heating, more of the benzene desorbed intact when potassium was present, instead of dissociat These elongated spots are seen after annealing ing to yield H2 and surface carbon. Interesting for a carbon coverage between 0.1 and 1.0 layers ly, in previous studies we showed that co-adsorbed of graphite-like carbon, as determined by Auger potassium substantially increased the platinum spectroscopy and hydrocarbon exposure. Both carbon bond strength for adsorbed CO. types of domains have always been observed together. The sharpness of spots is unchanged The adsorption of PF3, CH3CN, and C4H8 was over this range of coverage. Graphite-like car blocked by potassium, and no additional or shifted bon grows by island formation at low pressures on peaks were observed in the thermal desorption platinum(lll). spectra. Adsorbed NO, on the other hand, was found to dissociate in an amount proportional to Above one monolayer additional spots appear at the K concentration, yielding N? and N2O (as the radius of the graphite rings, ano these per well as NO) in the desorption spectra. sist after annealing at 1050-1100K. These addi tional spots form no obvious pattern and seem to We propose that only adsorbates having molecu be different each time the structure is formed. lar orbitals with energy levels located near to This suggests additional graphite-like layers are Ep can be significantly affected by "electronic forming out of registry with the first layer, as promotion" in catalysis. in bulk pyrographite. To order pyrographite requires annealing at 2000 - 3000 K, and carbon * * * diffuses into the bulk platinum above 1200 K. •"Brief version of LBL-15504. 9. THE COADSORPTION OF POTASSIUM AND CO ON THE Pt(lll) CRYSTAL SURFACE: A TDS, HREE".S, AND UPS 11. THE CHARACTERIZATION OF Pt/Cu ALLOY AND STUDY* EPITAXIAL SURFACES

J. E. Crowell, E. L. Garfunkel, and G. A. Somorjai R. Yeates and G. A. Somorjai

The interaction of CO with a potassium covered Copper deposited on the flat(lll) and Pt(lll) surface is investigated using thermal stepped(553) platinum crystal surfaces was studied desorption (TDS), high resolution electron energy with Auger electron spectroscopy (AES), thermal loss (HREELSj, and ultraviolet photoelectron {UPS) desorption spectroscopy (TDS), and low energy spectroscopies. When submonolayer amounts of electron diffraction (LEED). AES results indica potassium are preadsorbed, the adsorption energy ted that Cu grew on the Pt(lll) surface via a of CO increases from 25 to 36 kcal/mole, while layer-by-layer mechanism and via a Volmer-Weber substantial shifts in the site occupancy from the mechanism on the Pt(553) surface. LEED showed linear to the bridged site are observed. The CO that Cu formed islands on the Pt(lll) surface and stretching vibrational frequencies are shown to one monolayer of Cu took on the Pt lattice spacing decrease continuously with either increasing which is 8% larger than the Cu bulk lattice spac potassium coverage or decreasing CO coverage. A ing. The bulk Cu lattice spacing was reached minimum CO stretching frequency of 1400 cm-* is after 4 monolayers of Cu. These results indicate observed, indicative of a CO bond order of 1.5. a relatively strong Pt-Cu interaction. The work function decreases by up to 4.5 eV at submonolayer potassium coverages, but then in TDS of CO from Pt{lll)/Cu showed that epitaxial creases by 1.5 eV upon CO co-adsorption. The re Cu simply blocks adsorption sites of the Pt. The sults indicate that the large adsorption energy, change in the amount of CO desorption from the Pt vibrational frequency, and work function changes was directly proportional to the Cu coverage with 118

no desorption from Pt with £ 1 monolayer coverage atomic positions are of the order of the of Cu. No change in desorption energy was ob uncertainty of the determination (0.1 A). A served until high Cu coverages. TDS of CO from slightly larger contraction nf the top layer the Pt{553)-epitaxial Cu surface showed a prefer spacing is found here, which would translate to ential adsorption of the Cu away from the CO step about b% bond length contractions between atoms adsorption site. in the top layer and in the next layer. The best structure yields a five-R-factor average of 0.21, When a Pt crystal with a Cu adlayer was heated, a Zanazzi-Jona R-factor 2 x RRI3 of 0.34, and a the Cu diffused into the bulk. The activation Pendry R-factor 2 x RPE of 0.45. All other energy for this process was determined to be structural models in the long list that were 120 KJ/mole. The TDS of CO from the (111) face examined can now be rejected. of these Pt/Cu alloys showed a decrease in the * * * desorption energy of CO. The maximum decrease was 20 KJ/mole for a surface composed of 75* Cu. +Brief version of LBL-14338. ^University of Erlangen-Nurnberg, West Germany. 12. A NEW MODEL FOR CO ORDERING AT HIGH COVERAGES ON LOW INDEX METAL SURFACES: A CORRELATION 14. THE ADSORPTION AND BINDING OF THIOPHENE, BETWEEN LEED, HREELS, AND IRS. CO ADSORBED ON BUTENE, AND H?S ON THE BASAL PLANE OF MoS? fee (100) SURFACESt SINGLE CRYSTALS*

J, ?. Siberian and M. A. Van Hove M. Salmeron and G. A. Somorjai

We have reexamined the surface structures of The adsorption of thiophene,, butene, and H2S CO on (100) surfaces of copper, palladium, nickel, has been studied using the basal plane of M0S2 and platinum. We used the types of sites deter- single crystals in the temperature range of minad by High Resolution Energy Electron Loss 77-300 K. Only at the lowest temperatures did Spectroscopy (HREELS), or Infrared Spectroscopy thiophene adsorb and then desorb intact at 165 K (IRS), to propose new models for the arrangement using a partial pressure of 10-6 Torr. H?S of CO molecules at coverages exceeding 1/2, i.e., and butene behaved similarly and all of the mole at coverages higher than those corresponding to cules have binding energies in the range of 6-10 simple structures c(2 x 2) and p(2/2~ x /2)R45*. kcal/mole. Laser simulations allowed us to decide the valid ity of the proposed models. The consequences of * * * these models are the existence of at most two adsorption sites at all coverages, and the exist f ence of antiphase domains separated by walls to Brief version of LBL-13971. form the complex structures. The transition be tween iwo consecutive structures because of an increase of coverage is an unidirectional com 15. LEED AND AES STUDY OF ZIRCONIUM OVERLAYERS pression, generating more wall regions. ON THE Pt(lOO) CRYSTAL FACE * * * U. Bardi, P. N. Ross, and G. A. Somorjai Zirconium overlayers were deposited onto +Brief version of Surf. Sci. 118, 443 (1982). Pt(100) surfaces by electron beam evaporation under UHV conditions. A layer-by-layer growth mechanism was observed, which was maintained even 13. LEED INTENSITY ANALYSIS OF THE (1 x 5) when the zirconium was oxidized at low pressure RECONSTRUCTION OF Ir{100)+ between successive depositions. As-deposited zirconium was highly reactive toward oxygen, car E. Lang,* K. Muller,* K. Heinz,* M. A. Van Hove, bon monoxide, and hydrocarbons, rapidly forming R. J. Koestner, and G. A. Somorjai oxide or carbide, even at submonolayer coverages. Oxide 01 carbon overlayers were observed to New experimental LEED data for the reconstruc decompose upon UHV annealing at above ca. 700 K. ted Ir(100) (1 x 5) surface have been taken with with dissolution of the zirconium into the plati a videocamera coupled to a computer for the gen num substrate. The annealed oxide overlayers eration of I-V curves. Special attention was formed a variety of complex ordered Zr/O/Pt paid to minimize the effect of uncertainties in surface structures. Of particular interest was the angle of incidence {including those due to a reversible transformation between an oblique residual magnetic fields) and to assure proper background subtraction. epitaxial structure (lj\l) and the {300)-(l x 1) Pt structure, produced by oxygen dosing and re These data have been compared with existing versed by 900 K annealing. The epitaxial struc calculated LEED I-V curves to determine the ture is tentatively identified as a well-ordered surface structure. An R-factor comparison was PtZr^Oy surface phase, and the (1 x 1) structure made and the basic structural conclusion of the consisted of disordered Zr0~ islands on top of previous study has been confirmed, yielding a 21 quasi-hexagonal reconstructed top layer involving the (100) surface. The [yt] surface was unreac- bridge sites with respect to the underlying sub tive toward carbon monoxide or hydrocarbons, but strate layer. The top layer may be more buckled the (lxl) surface chemisorbed carbon monoxide than previously thought, but the differences in in a manner characteristic of Pt(100). 119

Studies of Catalyzed Surface Reactions 4. STUDIES OF SULFUR MONOLAYERS ON Mo(lOO) AND ITS EFFECTS ON ADSORBATE BINDING 1. AMMONIA SYNTHESIS CATALYZED BY RHENIUM1" A. Gellrnan, H. H. Farias, and G. A. Somorjai N. 0. Spencer and G. A. Somorjai The structure and chemical properties of Polycrystalline rhenium appears to be nearly sulfur deposits on a Mo(100) single crystal face an order of magnitude more active as an ammonia were studied. The sulfur deposits exhibit four synthesis catalyst than the most active crystal distinct LEED structures in the range of cover plane of iron [Fe(lll)] at low conversions and in ages from one monolayer to the clean surface, the the reactant pressure (20 atm) and temperature {603-713 K) regimes investigated. It displays an p(2 x 2), c(2 x 4), (jj) and c(2 x 2) struc activation energy for ammonia synthesis of 16.2 tures. The p(2 x 1) structure corresponds to one kcal mole"**, which is lower than that of Fe(lll) monolayer. The thermal desorption spectrum of (19.4 kcal mole-1) under identical experimental sulfur from Mo(lOO) indicates four distinct bind conditions. Although rhenium becomes reversibly ing sites* three at high energies, producing peaks poisoned at 1-2 Torr of product ammonia, exposure at 1100 K, 1400 K, and 1800 K, and the fourth at to water or presulfidation has little effect on 350 K. The low energy peak corresponds to adsorp its catalytic activity. This is in marked con tion of sulfur beyond the monolayer. trast to the behavior of iron. Thermal desorption studies of the effects of * + * sulfur on various molecules co-adsorbed on the Mo{100) surface were carried out. The molecules +Brief version of LBL-14298. studied to this point are D?, O2, CO, C2H4, n-hexane, and thiophene. The thermal desorption spectra have been studied as a function of sulfur 2. INTERACTION OF CO, CO?, AND D? WITH coverage. In all cases the sulfur poisoned the RHODIUM OXIDE: ITS REDUCTION AND CATALYTIC surface by blockage of adsorption sites. STABILITY The sulfur covered Mo(100) and the basal plane P. R. Watson and G. A. Somorjai of M0S2 were compared. Each has been exposed separately to Hg and O2 at pressures of 1 atm and We have investigated the adsorption and a temperature of 520 K. Under these conditions interaction of CO, CO2, and D? with RhgOs'SHgO by both surfaces were completely inert to the Hg thermal desorption spectroscopy (TDS). Both CO atmosphere- In the presence of 1 x 10-7 Torr of and D? react strongly with the oxide lattice 02-the sulfur on the Mo(lOO) surface was readily inducing decomposition during the desorption oxidized at temperatures of about 1100 K, and the process to yield COg and D2O. Adsorbed CO2 de- overlayer was removed as SO and SOg upon heating sorbs essentially in'.act. These results are com in vacuum. The ordered basal plant of H0S2 was pared with those found on rhodium metal formed by inert and showed no uptake of oxygen as examined reducing the oxide to the metallic state. On this by AES. However, after sputtering with He the metallic surface COg dissociates while CO and 0? M0S2 showed a marked uptake of oxygen and upon desorb without significant reaction. The use of heating evolved SO and S02- Sputtering has CO? to maintain an oxidized metal surface in a introduced defects into the surface, destroying reducing atmosphere during a catalytic reaction the ordered structure seen by LEED, and these was investigated. defect sites are now vulnerable to attack by O2.

3. DEUTERIUM ISOTOPE EFFECTS FOR HYDROCARBON 5. THE EFFECT OF POTASSIUM ON THE CATALYZED REACTIONS CATALYZED OVER PLATINUM SINGLE CRYSTAL REACTIONS OF n-HEXANE OVER Pt(lll) AND SURFACES* Pt-[6(lll)x{lll)] SINGLE CRYSTAL SURFACES

S. M. Davis, W. D. Gillespie, and G. A. Somorjai F. Zaera and G. A. Somorjai

The initial rates of hydrocarbon reactions of The effect of potassium on the n-hexane isobutane, neopentane, cyclohexane, n-hexane, and conversion catalyzed by Pt(lll) and n-heptane, in the presence of deuterium, were Pt[6(lll)x(lll)] single crystals has been studied measured over the flat (111), stepped (13,1,1), near atmospheric pressures. Reaction activity, and kinked (10,8,7) platinum single crystal sur selectivity, and self-poisoning with time were faces in the temperature range 520-650 K and at studied as a function of potassium coverage of atmospheric pressures. Inverse isotope effects the crystal faces. The activity of the catalyst [(RD/RH) = 1-3-3,3] were detected for a variety dropped drastically with as little as 2% potas of hydrogenolysis, isomerization, and C5- sium atoms on the surface, with no improvement in cyclization reactions. The inverse isotope selectivity or stability. The temperature depend effects that appear to arise from a combination ence in the range 550-600 K of the reaction rates of kinetic and thermodynamic isotope effects dis was not significantly different from the clean played magnitudes that were not much dependent on platinum case. the platinum surface structure. * * * The change in the structure of the carbonaceous deposits formed during the reaction has also been +Br1ef versio, of LBL-13363. studied. The variations with potassium coverage 120

of the total amount of carbon, the fraction of distribution, as compared to crystal temperature, uncovered platinum, the hydrogen content, and the is found to be consistent with different desorp energetics of dehydrogenation of these deposits tion kinetics for N0(\>" = 0) and N0(vH * 1) were investigated. The inhibition of the de adsorbed molecules at crystal temperatures be hydrogenation of adsorbed hydrocarbon species in tween 450-1000 K. At temperatures above 1000 K, the presence of co-adsorbed potassium on the a competition between vibrational excitation and platinum surface explains the changes of reactiv molecular desorption is proposed to explain the ity that are reported.. increased deviation between the observed vibra tional distribution and the expected one, if a complete accommodation with the crystal surface 6. DEHYDR0GENAT70N OF CYCLOHEXANE CATALYZED 3Y occurs. BIMETALLIC Au-Pt SINGLE CRYSTAL SURFACES* * * * J. W. A. Sachtler and G. A. Somorjai +Brief version of LBL-13347 and LBL-15034. The cyclohexane dehydrogenation was investi gated using two-phase, epitaxial Au on Pt(lll) single crystal surfaces and single-phase Au- 1982 PUBLICATIONS AND REPORTS Pt(lll) surface alloys as catalysts, with 20 mbar cyclohexane and 133 mbar H^ at 573 K. Benzene Refereed Journals production was found to be enhanced 4.5-9 fold on surfaces containing about 50 at.% Au. The clean 1. S. Ferrer, J. M. Kojo, M. Salmeron, and G. A. Pt(lll) crystal face did not produce detectable Somorjai, "The Role of Surface Irregularities amounts of cyclohexene, its formation being com (Steps, Kin(>J and Point Defects on the Chemical pletely attributable to the crystal edges. How Reactivity of Solid Surfaces," Philosophical ever, the addition of gold to the Pt(lll) surface Magazine 45(2), 261 (1982). induced production of cyclohexene, surfaces con taining about 90 at.% Au being most active. The 2. S. M. Davis and G. A. Somorjai, "Surface effects were similar for epitaxial and alloy sur Reactions," Encyclopedia of Materials Science and faces, although the latter usually gave higher Engineering, edited by M. B. Bever, Pergamon rates. Cyclohexene hydrogenation and dehydrogena Press, New York, (1982); LBL-12372. tion catalyzed by a Pt(100) single crystal sur face, using 13.3 mbar cyclohexene ar.d 13.3 mbar H2 at 373 K, was only found to be inhibited by 3. R. J. Koestner, J. C. Frost, P. C. Stair, an epitaxial Au overlayer. The enhancement by Au M. A. Van Hove, and G. A. Somorjai, "Evidence For of the cyclo'iexane dehydrogenation to benzene is The Formation of Stable Alkylidyne Structures from interpreted is n reduction of the poisoning of Pt C3 and C4 Unsaturated Hydrocarbons Adsorbed on sites by benzt.ie and possibly carbonaceous resi the Pt(lll) Single Crystal Surface," Surf. Sci. dues at high temperatures. The observation that 116, 85 (1982); LBL-12780. only Au containing Pt(lll) surfaces produced cyclohexene can be explained by ensemble size 4. M. A. Van Hove and G. A, Somorjai, "Dynamical effects. and Approximate LEED Theories Applied to Layers of Large Molecules," Surf. Sci. 114, 171 (1982); * * * LBL-12803. 5. M. Salmeron and G. A. Somorjai, "The Desorp +Brief version of LBL-14406. tion, Decomposition, and Deuterium Exchange Reactions of Unsaturated Hydrocarbons (Ethylene, Acetylene, Propylene, and Butenes) on the Pt(lll) 7. ENERGY REDISTRIBUTION AMONG INTERNAL STATES Crystal Face," J. Phys. Chem. 86, 341 (1982); OF NITRIC OXIDE MOLECULES UPON SCATTERING FROM LBL-12857. — Pt(lll) CRYSTAL SURFACE"*" 6. P* W. Davies, M. Quinlan, and G. A. Somorjai, M. Asscher, W. L. Guthrie, T.-H. Lin, and G. A. "The Growth and Chemisorption Properties of Ag Somorjai and Au Monolayers on Platinum Single Crystal Surfaces: An AES, TDS, and LEED Study," Surf. The vibrational and rotational states distribu Sci. 121, 290 (1982); LBL-12946. tions of a supersonic nitric oxide beam, scattered from a Pt{lll) single crystal surface, were 7. G. A. Somorjai, "The Surface Science of investigated as a function of crystal temperature Heterogeneous Catalysis: Possible Application in and scattering angle. A two-photon ionization Atmospheric Sciences," presented at Atmospheric technique was applied to monitor the internal Chemical Society Conf. on Atmospheric Sciences, energy content of the scattered molecules. The Albany, NY; Heterogeneous Atmospheric Chemistry extent of equilibration of the three degrees of Geophysical Monograph Series 26, 88 (1982); freedom of the NO molecule, e.g., translation, LBL-12986. rotation, and vibration, as monitored by means of the accommodation coefficient (y) was found to be 8. G. A. Souiorjai, "Study of the Structure of ytrans>7vib>Yrot. The small rotational degree of Adsorbed Molecules on Solid Surfaces by HREELS accommodation is proposed to originate from a and LEED," Proc. 9th Intl. Conf. on Atomic Spec preferential desorption of rotationally cold NO troscopy, XXII CSI, Tokyo, Sept. 1981, Recent molecules, as can be rationalized by microscopic Advance in Analytical Spectroscopy, edited by reversibility arguments. The cold vibrational K. Fuwa, Pergamon Press, p. 211 (1982); LBL-12996. 9. W. McLean, C. A. Colroenares, R. L. Smith, and (10-8-105 Torr)," Rev. Sci. Instrum. 53(12), 1888 G. A, Somorjai, "Electron Spectroscopy Studies of (1982); LBL-13995. the Clean Thorium and Uranium Surfaces. The Chemisorption and Initial Stages of Reaction With 21. N. D. Spencer and G. A. Somorjai, "Rhenium—

02, CO, and C02," Phys. Rev. B 25(1), 8 (1982); An Ammonia Synthesis Catalyst," 0. Phyc. Chem. UCRL-86167. Lett. 86, 3493 (1982); LBL-14134.

10. H. Langell and G. A. Somorjai, "The Composi 22. J. P. Biberian and M. A. Van Hove, "A New tion and Structure of Oxide Films Grown on the Model for CO Ordering at High Coverages on Low- (110) Crystal Face of Iron," J. Vac. Sci. Technol. Index Metal Surfaces: A Correlation Between 21, 858, (1982); LBL-13203. LEED, HREELS and IRS. I. CO Adsorbed on fcc(lOO) Surfaces," Surf. Sci. 118, 443 (1982). 11. E. L. Garfunkel and G. A. Somorjai, "Potas sium and Potassium Oxide Monolayers on the 23. R. J. Koestner, M. A. Van Hove, and G. A. Pt(lll) anH Stepped (755) Crystal Surfaces: A Somorjai, "A LEED Crystallography Study of the LEED, AES and TDS Study," Surf. Sci. U5_, 441 (2x2)-C2H3 Structure Obtained After Ethylene (1982); LBL-13293. Adsorption on Rh(lll), Surf. Sci. 121, 321 (1982); LBL-13598. 12. N. 0. Spencer, R. C. Schoonmaker, G. A. Somorjai, "Iron Single Crystal as Ammonia Synthe 24. N. D. Spencer and G. A. Somorjai, "Ammonia sis Catalysts: Effect of Surface Structure on Synthesis Catalyzed by Rhenium," J. Catal., 78, Catalyst Activity," J. Catal. 74, 129 (1982); 142 (1982); LBL-14298. LBL-13294. LBL Reports 13. M. A. Van Hove, R. J. Koestner, and G. A. Somorjai, "The Structures of Small Hydrocarbon 1. S. M. Davis and G. A. Somorjai, "Catalysts by Molecules on Rh(lll) Studied by Low Energy Elec Platinum," submitted to Scientific American, tron Diffraction: Acetylene, Ethylene, Methyl- LBL-13163. acetylene, and Propylene," J. Vac. Sci. Technol. 20(3), 886 (1982); LBL-13300. 2. S. M. Davis, W. D. Gillespie, and G. A. Somorjai, "Deuterium Isotope Effects for Hydro 14. T.-H. Lin, S. T. Ceyer, W. L. Guthrie, and G. carbon Reactions Catalyzed over Platinum Single A. Somorjai, "The Angular and Velocity Distribu Crystal Surfaces," submitted to J. Phys. Chem., tion of NO Scattered from the Pt(lll) Crystal LBL-13363. Surface," J. Chem. Phys. 76, 6398 (1982); LBL-13347. 3. S. M. Davis, F. Zaera, and G. A. Somorjai, "Surface Structure and Temperature Dependence of 15. E. L. Garfunkel, J. E. Crowell, and G. A. Light Alkane Skeletal Rearrangement Reactions Somorjai, "The Strong Influence of Potassium on Catalyzed Over Platinum Single Crystal Surfaces," the Adsorption of CO on Platinum Surfaces: A TDS submitted to J. Am. Chem. Soc, LBL-13975. and HREELS Study," J. Phys. Chern. 86, 310 (1982); LBL-13349. 4. C. Minot, M. A. Van Hove, and G. A. Somorjai, "A Covalent Model for the Bonding of Adsorbed 16. J. E. Katz, P. W. Davies, J. E. Crowell, and Hydrocarbon Fragments On the (111) Face of Plati G. A. Somorjai, "Design and Construction of a High num," LBL-13603. Stability, Low Noise Power Supply for Use with High Resolution Electron Energy Loss Spectrom 5. A. Gavezzotti, M. Simonetta, M. A. Van Hove, eters," Rev. Sci. Instrum. 53(6), 785 (1982); and G. A. Somorjai, "Force-Field Calculations of LBL-13437. the Packing Energy of Monolayers of C3 and C4 Hydrocarbon Molecules Adsorbed on Single Crystal 17. F. Zaera and G. A. Somorjai, "Review: Metal Surfaces," submitted to Surf. Sci., Heterogeneous Catalysis on the Molecular Scale." LBL-14053. J. Phys. Chem. 86, 3070 (1982); LBL-13551. 6. G. A. Somorjai, "The Surface Science of 18. S. M. Davis, F. Zaera, and G. A. Somorjai, Heterogeneous Catalysis," to be published in "The Rfactivity and Composition of Strongly Robert A. Welch Conference Proceedings, LBL-14135. Adsorb*d Carbonaceous Deposits on Platinum. Model of the Working Hydrocarbon Conversion 7. S. M. Davis and G. A. Somorjai, "The Surface Catalyst," J. Catal. 77, 439 (1982); LBL-13706. Science of Heterogeneous Catalysis," to be published in Chemtech, LBL-14285. 19. M. Salmeron, A. Wold, R. Chianelli, and G. A. Somorjai, "The Adsorption and Binding of 8. R. J. Koestner, M. A. Van Hove, and G. A.

Thiophene, Butene and H2S on the Basal Plane of Somorjai, "The Structure and Bonding of Hydro MoSj Single Crystals," Chem. Phvs. Lett. 90, 105 carbons Adsorbed on Metal Surfaces," to be (1982); LBL-13971. published in Chemtech, April 1982, LBL-13982. 20. A. L. Cabrera, N. D. Spencer, E. Kozak, P. W. 9. J. E. Crowell, E. L. Garfunkel, and G. A. Davies, and G. A. Somorjai, "Improved Instru Somorjai, "The Co-adsorption of Potassium and CO mentation to Carry Out Surface Analysis and to on the Pt(lll) Crystal Surface: A TDS, HREELS Monitor Chemical Surface Reactions In Situ on and UPS Study," to be published in Surf. Sci. Small Area Catalysts Over a Wide Pressure Range LBL-14335. 122

10. E. Lang, K. Muller, K. Heinz, M. A. Van Hove, Revealed by Single Crystals Studies," and "The P.. 0. Koes+;ier\ and G. A. Somorjai, "LEEO Inten Reactivity of Metal Monolayers on Single Crystal sity Anal-sis of the (1 x 5) Reconstruction of Surfaces of Other Metals: Gold, Silver. >*opper IR(100). to be published in Surf. Sci., and Potassium on Platinum," ACS Meeting, Symposium LBL-143J8. on "Multimetallic Catalysis," Las Vegas, Nevada, March 19, 1982. 11. J. W. A. Sachtler and G. A. Somorjai, "Influ ence of Ensemble Size on CO Chemisorption and 2. G. A. Somorjai, "Studies of Metal and Organic Catalytic n-Hexane Conversion with Au-Pt(lll) Bi Monolayers by Electron Scattering," The University metallic Single Crystal Surfaces," to be published of Tokyo, Tokyo, Japan, April 5, 1982. in J. Catal., LBL-14406. 3. G. A. Somorjai, "The Atomic Structures of 12. R. J. Koestner, M. A. Van Hove, and G. A. Surface Monolayers. The Surface Chemical Bond," Somorjai, "The Molecular Structure of Hydrocarbon Fudan University, Shanghai, China, April 8, 1982. Monolayers on Metal Surfaces," to be published in J. Phys. Chem., LBL-13962. 4. G. A. Somorjai, "Catalysis of Hydrocarbon Conversion," Fudan University, Shanghai, China, 13. H. Salmeron, R. Chianelli, and G. A. April 9, 1982. Somorjai, "A LEED-AES Study of the Structure of Sulfur Monolayers on the Mo(100) Crystal Face," 5. G. A. Somorjai, "The Modern Techniques of to be published in Surf. Sci., LBL-14551. Analyzing the Properties of Surfaces," Beijing University, Beijing, China, April 15, 1982. 14. G. A. Somorjai, "Molecular Ingredients of Heterogeneous Catalysis, International Academy of 6. G. A. Somorjai, "The Atomic Structures of Quantum Molecular Science, 4th International Surface Monolayers. The Surface Chemical Bond," Congress iii Quantum Chemistry," Uppsala, Sweden, Beijing University, 8eijing, China, April 17, June 19Q2, LBL-14531. 1982.

15. B. E. Koel, M. A. Van Hove, and G. A. 7. G. A. Somorjai, "Principles of Heterogeneous Somorjai, "LEED and HREELS Studies of Molecular Catalysis. Elementary Surface Reactions," Jilin Adsorbates on Model Catalyst Surfaces," Advances University, Changchun, China, April 20, 1982. in Catalytic Chemistry II Symposium, Salt Lake City, Utah, LBL-14504. 8. G. A. Somcrjai, "Catalysis of Hydrocarbon Conversion," Jilin University, Changchun, China, 16. M. A. Van Hove, R. J. Koestner, and G. A. April 21, 1982. Somorjai, "LEED Intensity Analysis of a Surface Structure With Three CO Molecules in the Unit 9. G. A. Somurjai, "Relation Between Surface Cell, Rh(lll)(2x2)-3C0: Compact Adsorption in Science and Catalysis. New Developments," Jilin Simultaneous Bridge and Non-Symmetric Neat-Top University, Changchun, China, April 24, 1982. Sites," submitted to Phys. Rev. Lett., LBL-15033. 10. G. A. Somorjai, "ELS and LEEO Studies of 17. M. Asscher, W. L. Guthrie, T.-H. Lin, and Catalyst Surfaces," Salt Lake City, Utah, May 19, G. A. Somorjai, "Energy Redistribution Among 1982. Internal States of Nitric Oxide Molecules Upon Scattering From Pt(lll) Crystal Surface," sub 11. G. A. Somorjai, "Molecular Ingredients of mitted to J. Chem. Phys. LBL-15034. Heterogeneous Catalysis," 4th International Congress in Quantum Chemistry, Uppsala, Sweden, 18. S. T. Ceyer, W. L. Guthrie, and T.-H. Lin, June 19, 1982. "O2O Product Angular and Translational Energy Distributions From the Oxidation of Deuterium on 12. G. A. Somorjai, "Structure of Atoms and Pt(lll)," submitted to J. Chem. Phys., LBL-15035. Molecules or Solid Surfaces," American Crystal- lographic Association Meeting, San Diego, 19. R. Casanova, A. L. Cabrera, H. Heinemann, and California, August 17, 1982. G. A. Somorjai, "Calcium Oxide and Potassium Hydroxide Catalyzed Low Temperature Methane Pro 13. G. A. Somorjai, "Surface Science of Hetero duction From Graphite and Water. Comparison of geneous Catalysis," Philadelphia Catalysis Soci Catalytic Mechanisms," submitted to Fuel, ety, Philadelphia, Pennsylvania, September 8, LBL-15067. 1982.

?0. S. M. Davis, F. Zaera, M. Salmeron, R. Gordon, 14. G. A. Somorjai, "Surface Science of Hetero and G. A. Somorjai, "Energetics and Reversibility geneous Catalysis of Metal Surfaces," Illinois of Hydrocarbon Sequential Dehydrogenation on Institute of Technology, Kilpatrick Lecture, Platinum Single Crystal Surfaces: Thermal Desorp- Chicago, Illinois, October 14, 1982. tion and Carbon-14 Radiotracer Studies," to be published in J. Am. Chem. Soc, LBL-14611. 15. G. A. Somorjai, "Toward Energy Independence Through Research in Surface Chemistry and Cataly sis;" "The Structure of Adsorbed Monolayers, The Invited Talks Surface Chemical Bond;" and "T';e Molecular Ingre dients of Catalyzed Hydrocarbon Conversion Over 1. G. A. Somorjai, "The Structure Sensitivity of Transition Metals," Michigan State University Dow Platinum Catalysts for Reforming Reactions as Lectures, Michigan, October 26-28, 1982. 123 16. G. A. Somorjai, "The Materials Science of 20. M. A. Van Hove, "LEED Determination of the Heterogeneous Catalysis," Stanford University, Structures of Adlayers Containing More Than One Palo Alto, California, November 2, 1982. Molecule per Unit Cell: CO and Propylidyne on Rh(lll), 5th European Conference on Surface 17. G. A. Somorjai, "The Structure and Composi Science, Ghent, Belgium, August 25, 1982. tion of Solids in the Near Surface Region," U.S. Army Research Office, Metallurgy and Materials 21. M. A. Van Hove, "Structures d'hydrocarbures a Division, Department of the Army, Charleston, pe'riodicite' bidimensionnelle par diffraction South Carolina, December 14, 1982. d'Slectrons lents," University of Marseille, France, September 3, 1982. 18. M. A. Van Hove, "Structural Study of CO Mole cules Adsorbed Simultaneously in Linear and Bridge 22. M. A. Van Hove, "High-Coverage Structure of Sites in Rh(lll)+(2x2)3C0 by LEED Intensity Calcu CO on Rh(lll)," Autonomous University of Madrid, lations," American Physical Society Meeting, Spain, September 8, 1982. Dallas, Texas, March 9, 1982. 23. M. A. Van Hove, "Physical Aspects of the 19. M. A. Van Hove, "What Can Structural Deter Structure and Bonding of CO on Metal Surfaces," mination by LEED Do?" IBM Research Laboratory, Department of Physics, University of California, San Jose, California, June 1, 1982. Berkeley, October 13, 1982. 124

f. Nuclear Magnetic Resonance*

Alexander Pines, Investigator

Introduction. The primary objectives of this 2. TIME-RESOLVED OPTICAL NUCLEAR POLARIZATION* program are to develop new methods in magnetic resonance spectroscopy and to use them to study R. Tycko, D. Stehlik,* H. Cho, and A. Pines molecular behavior in condensed phases. This de mands an understanding of the interaction of nu We have developed a new technique for study clear spins with each other, with other degrees ing dynamic processes in the excited triplet of freedom such as molecular translations, vibra electronic state of molecular crystals on a tions and rotations, and with external radiation microsecond time scale. The technique, called such as light or radiofrequency sources. Recent time-resolved optical nuclear polarization, novel methods developed under the program include freezes information about the transient excited multiple quantum spectroscopy, high resolution states in the form of long-lived nuclear magneti solid state NMR and magic angle spinning, pulsed zation, where it can subsequently be read out by optical nuclear double resonance, and nuclear pulsed NMR techniques. The nuclear magnetization magnetic isotope separation. These methods are is generated by a sequence of precisely timed ul being applied to understand structure and dynam traviolet laser pulses and magnetic field pulses. ics at the molecular level in a number of mater Measurement of the nuclear magnetization as a ials including ferroelectrics, liquid crystals, function of decay times within the sequence, when polymers, organic crystals, and zeolites. Some interpreted according to the detailed theory of molecular properties change upon light excitation, optical nuclear polarization, yields parameters and laser magnetic double resonance is being used such as the excited state lifetime and excited to examine how these changes dictate the course state spin relaxation times. The utility of the of photochemical reactions. technique has been demonstrated on single-crystal samples of fluorene doped with acridine. The time-resolved technique also shows promise for the generation of large nuclear magnetization in 1. BROADBAND POPULATION INVERSION''' samples or at room temperature where conventional optical nuclear polarization techniques fail. J. Baum, R. Tycko, J. Murdoch, and A. Pines

The optimal use of power in a spectroscopic experiment demands that power be absorbed as uni formly as possible over a broad band of frequen +Abstracted in part from LBL-14929; Chem. Phys. cies. We have developed an approach to the design Lett. 93, 392 (1982). of phase-shifted, radiofrequency-pulse sequences ^Department of Physics, Free university of Berlin. that have the ability to invert nuclear spin pop ulations over a broad range of resonance frequen cies. Previous work in this area has relied upon 3. ZERO FIELD tMf a pulse-by-pulse analysis of the inverting se quence. Our approach takes as its starting point D. Weitekamp,* A. Bielecki, D. Zax, and A. Pines a particular inverting trajectory for the on-resonance spins. A pulse with a continuously varying Structural information on molecales in solids phase can be derived from that trajectory. Com must typically be obtained using x-ray diffrac puter simulations show that, for the proper on- tion or NMR on single crystals. In powders the resonance trajectory, the inverting property of spectra are broadened and orientational informa the derived pulse holds for off-resonance spins tion is lost. Consider, however, what would hap as well. Several mathematical methods for ap pen if the isotropy of space was not broken by proximating the continuously varying pulse by a some preferred direction, e.g., the beam of x rays sequence of constant phase pulses have been in or the magnetic field. The spectrum of a powder vestigated. Applications are also possible in could then look like that of a single crystal and wideband coherent optical excitation with lasers. yield full structural information. This is the basis of zero field NMR, in which the cycling of magnetic fields in a two-dimensional NMR experi ment allows us to obtain the dimensional NMR "^Abstracted in part from LBL-14206; J. Chem. spectrum without any applied external field. Phys. 2Z. 2870 (1982). Indeed, the powder spectra of solid BajC^^HgO and Li2S04*H20 exhibit well resolved lines yield ing structural information without the need for single crystals.

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sci ences, Materials Sciences Division of the U.S. ^Abstracted in part from LBL-10593. Department of Energy under Contract No. •^Department of Chemistry, University of Groningen, DE-AC03-76SF00098. The Netherlands. 125

4. ANISOTROPIC DIFFUSION IN ORIENTED SYSTEMS1" a. ISM for quadrupolar nuclei in .he absence of interactions with external energy reservoirs. D. Zax and A. Pines * * * Molecular diffusion in oriented systems such Âbstracted in p*rt from LBL-15686. as polymers and liquid crystals is anisotropic. ^Central Research Division, Du Pont. The degree of anisotropy is an important parame ^Department of Chemistry, University of ter in understanding the interactions between Groningen, The Netherlands. molecules in these phases. Measurements have been made, using a new multiple quantum spin echo technique developed in our laboratory, on benzene and butyne in Eastman nematic phase 15320. The 7. TIME-RESOLVED CIDNP AND MAGNETIC ISOTOPE results show a significant enhancement of diffu EFFECT* sion parallel to the director axis and suggest a model in which the shape of the solute molecules L. Sterna,* J. F .«I, and A. Pines determine diffusion effects. A very important feature of free radical chen.- istry is the effect of electron spin on chemical * * * bonding. In general, two radicals can bond only if the two unpaired electrons have singlet (S = Âbstracted in part from LBL-14997. 0) correlation. The triplet state (S = 1) has repulsive potentials. The electron-nuclear hyperfine coupling causes interconversion of the 5. HIGH RESOLUTION NMR OF FELDSPARS AND ZEOLITES* electron spin states. This can be used to separ ate nuclear isotopes of different hyperfine coupl J. M. Millar, J. B. Murdoch, C. Ye, R. Eckman,* ing into different chemical products (Magnetic and A. Pines Isotope Effect). A crucial factor in the opera tion of the magnetic isotope effect in a cyclic Magic-angle spinning (MAS) NMR is an ideal reaction is that the two radicals of the prepared technique for the study of complicated solids: triplet must stay in the vicinity of one another all anisotropic nuclear spin interactions are on a timescale comparable to the inverse hyper averaged to zero, leaving a liquid-like spectrum fine couplings. In previous reports we have of isotropic chemical shifts. We have obtained shown that the *3c enrichment in the diben- high-resolution *H, 'H, 27A1, and 29Si MAS NMR zylketone reaction exhibits a strong viscosity spectra of a variety of feldspars, zeolites, and dependence and goes through a maximum at 10 poise. other alumino-silicates of importance in catalysis Current work involves time-resolved CIDNP in cy and earth science. Such spectra provide detailed clic reactions of ketones and long chins to try information on coordination numbers and on the and enhance the isotope effect. The time resolu nature and extent of silicon-aluminum ordering in tion is obtained by using a pulsed N2 laser, with these materials. Of particular interest are rap a high power pulsed NMR spectrometer. idly quenched feldspar glasses in that their structure may mirror that of the corresponding liquids. * * * * * * Âbstracted in part from LBL-10594. *Shell Development Company, Houston. '''Abstracted in part form L8L-15254. ^Central Research Division, Du Pont. 8. MOLECULAR CONFORMATION IN LIQUID CRYSTALS*

6. THEORY OF SPIN DIFFUSION IN SOLIDS* G. Drobny, 8. Oh, H. Fujiwara, and A. Pines

R. Eckman.* A. Pines, R. Tycko, and 0. P. The study of the conformation of aromatic and WeitekampS aliphatic units in liquid crystal molecules is important in understanding the physics and chem Spin diffusion in solid-state NMR occurs by istry of their various fascinating phases. This the exchange of one quantum of energy in flip-flop can usually only be accomplished with deuterium transitions driven by dipole couplings. It is isotope substitution and complex analysis of the commonly believed that flip-flop transitions are NMR spectra. However, multiple quantum transi quenched when the nuclei involved have well-sep tions are extremely sensitive to correlations, arated resonance frequencies, as is generally the both static and dynamic, between the protons of a case for inequivalent quadrupolar nuclei. An av molecule and are usually resolvable and simple to erage Hamiltonian theory of flip-flop transitions analyze. We have used this to study the confor reveals that a second order process allows a gen mations of a number of liquid crystal systems and eralized flip-flop in which nuclei exchange two the relationship of these conformations to the quanta of energy. We derive a detailed expression macroscopic phases. For example, in the nematic for the rate of this double-quantum flip-flop, phase of cyanobiphenyl systems, the conformation showing the dependence of the rate on the dipole of the biphenyl group could be analyzed by fit coupling strength and on the difference in qua- ting the 6- and 7-quantum spectra (the normal drupole splittings for a pair of inequivalent 1-quantum spectrum has 1000 lines and can iardly spin-1 nuclei. We expect the double-quantum be analyzed) to theoretical models of the order flip-flop to be the dominant spin diffusion mech- parameters and biphenyl dihedral angle. 126

Aliphatic chain configurations can also be 5. D. P. Weitekamp, J. R. Garbow, and A. Pines, studied, since the multiple quantum spectra are "Determination of Dipole Coupling Constants Using extremely sensitive to inter-segment dipole-dipole Neteronuclear Multiple Quantum NMR," J. Chem. couplings. The best fit is found to be a model Phys. 77, 2870 (1982); LBL-14206. with all trans and two conformations with gauche defects. 6. R. Tycko, D. Stehlik, and A. Pines, "Time-Re solved Optical Nuclear Polarization," Chem. Phys. * * * Lett. 93, 392 (1982); LBL-14829.

^Abstracted in part from LBL-13736. 7. J. R. Garbow, D. P. Weitekamp, and A. Pines, "Bilinear Rotation Decoupling of Homonuclear Scalar Interactions," Chem. Phys. Lett. 93, 504 9. EXCITATION OF HIGH N-QUANTUM TRANSITIONS* (1982); LBL-14904. ~

W. S. Warren,* D. P. Weitekamp,§ Y. S. Yen, J. R. Garbow, and A. Pines LBL Reports

The question of whether a molecule can be used 1. Y. S. Yen and A. Pines, "Multiple-Quantum NMR to absorb and emit photons only in groups of n has in Solids," LBL-14821, J. Chem. Phys,, in press. been treated further. A number of pi lse sequences have been introduced, which in effect induce ex 2. 0. Zax and A. Pines, "Study of Anisotropic citation by onl i resonant groups of n photons. Diffusion of Oriented Molecules by Multiple Quan This causes only n-quantum transitions even when tum Spin Echoes," LBL-14997. many other transitions might be resonant. The theory explains how this is done by using repeated 3. Y. S. Yen, "Multiple Quantum NMR in Solids," phase shifts of 2/n in the radiation to build up Ph.D. thesis, LBL-15253. thp selected coherences with all other coherences interfering destructively. The selectivity pro 4. J. B. Murdoch, "Computer Simulations of duces an enormous enhancement of the high n-quan- Multiple Quantum Spectroscopy," Ph.D. thesis, v.um coherences (or populations) that are normally LBL-15254. very weak when governed by an incoherent statis tical process. For example, the 12-quantum trans 5. R. Eckman, "High Resolution NMR in Solids ition in a many spin crystal can be enhanced by with Magic Angle Spinning," Ph. D. thesis, four or five orders of magnitude. Up to 22-quan- LBL-14200. tum excitations have been observed in solid ada- mantane. 6. G. Drobny, "NMR Studies of Liquid Crystals and Molecules Dissolved in Liquid Crystals," * * * Ph.D. thesis, LBL-13736.

*Abstracted in part from L8L-15253 and Chem. 7. D. P. Weitekamp, "Time Domain Multiple Phys. Lett. 88, 441 (1982). Quantum NMR," Ph.D. thesis, LBL-10593. $ Department of Chemistry, Princeton university. §Oepartment of Chemistry, University of 8. R. Eckman, R. TycKa, D. Weitekamp, and A. Groningen, The Netherlands. Pines, "Deuterium Spin Diffusion by Double Quantum Flip-Flops," LBL-15686.

Invited Talks

1. A. Pines, "New Angles and Dimensions in NMR," 1982 PUBLICATIONS AND REPORTS Royal Society of Chemistry, Birmingham, England, March 1982. Refereed Journals 2. A. Pines, "New Angles in NMR," The California 1. R. Eckman and A. Pines, "High Resolution Catalysis Society Annual Spring Meeting, Pleasan- Proton NMR of Dilute Spins in Solids," J. Chem. ton, California, April 16, 1982. Phys. 75, 2767 (1982); LBL-13332. 3. A. Pines, J. R. Garbow, D. P. Weitekamp, and 2. D. P. Weitekamp, J. R. Garbow, and A. Pines, V, I. Yen, "Free Induction Decay—Where Does It "Search Procedure for Optimizing High Order Go?" 23rd Experimental NMR Spectroscopy Confer Multiple Quantum Transition Intensities," J. ence, Madison, Wisconsin, April 1982. Magn. Res. 46, 529 (1982); LBL-13557. 4. A. Pines, R. Eckman, C. Ye, and J. M. Millar, 3. Y. S. Yen and D. P. Weitekamp, "Indirect "Magic Ar.nle spinning of ^H/22H and Other Detection of Spin 1 Double Quantum Coherence in Nuclei," 23rd Experimental NMR Spectroscopy Liquids," J. Magn. Res. 47., 476 (1982); LBL-13434. Conference, tadison, Wisconsin, April 1982.

4. W. S. Warren and A. Pines, "Simple Pulse 5. R. Eckman, "High Resolution Proton and Sequences for Selective Multiple-Quantum Ex Deuterium NMR in Solids," American Chemical citation," Chem. Phys. Lett. 88, 441 (1982); Society Middle Atlantic Regional Meeting, LBL-13006, University of Delaware, Newark, April 1982. 127

6. A. Pines, 7th Ampere International Summer 9. A. Pines, Chemistry Department Seminar, School on New Techniques and Applications of Pomona College, Claremont, California, October Magnetic Resonance, 3 invited lectures. Portoroz, 1982. Yugoslavia, June 1982. 10. A. Pines, Chemistry Department Seminar, 7. A. Pines, "Multiple Quantum Spectroscopy," University of Arizona, Tuscon, Arizona, October Institute of Experimental Physics, University of 1982. Stuttgart, Seminar, Germany, June 21, 1982. 11. A. Pines, Chemistry Department Seminar, San 8. A. Pines, "New Angles in Solid State NHR," Jose State University, Scu Jose, California, 24th Rocky Mountains Conference, 4th Vaughan November 1982. Plenary Lecture, Denver, Colorado, August 1982. Chemical Sciences 129

A. Fundamental Interactions y

1. Photochemical and Radiation Sciences

a. Photon-Assisted Surface Reactions, Materials, and Mechanisms*

Gabor A. Somorjai, Investigator

Introduction. This project explores the Water dissociation experiments have also been photocatalyzed dissociation of water (HgO) at carried out in the vapor phase. Samples consist both the solid-liquid and solid-v?por interfaces ing of p-type Hg-doped and n-type Si-doped iron to produce hydrogen and oxygen gases. The purpose oxides were pressed together to form a contact of these studies is to explore the mechanism of junction. The disks were exposed to water vapor the photon-assisted surface reaction, to charac in a high pressure cell in an ultrahigh vacuum terize the semiconductor catalyst, and to estab chamber. Visible light from the solar spectrum lish the optimum conditions {of surface structure, was shone on the samples, and oxygen evolution composition, temperature, and electrolyte solu was monitored with a mass spectrometer. Surface tion) that maximize the rate of hydrogen and oxy analyses of the sample before and after the gen production and the power conversion efficiency photodissociation experiments were done with an of the process. The materials that are being used Auger spectrometer in the UHV chamber to deter include silicon- and magnesium-doped iron oxides mine whether the oxidation state of the iron was and molybdenum and rhenium sulfides. changing during the photodissociation process.

Surface characterization and sample analysis 1. PHOTOCATALYTIC PRODUCTION OF HYDROGEN FROM with Auger and x-ray photoelectron spectroscopy WATER BY A p- AND n-TYPE POLYCRYSTALLINE IRON as well as detailed studies of the photoactivity OXIDE ASSEMBLY* of the iron oxide disks are being carried out.

C. Leygraf, M. Hendewerk, and G. A. Somorjai * * *

Photodissociation of water using Mg- and +Brief version of LBL-14494 and LBL-14560. Si-doped iron oxides has been accomplished in a p/n diode assembly utilizing only visible light and applying no external bias. While iron oxides 2. THE PREPARATION AND SELECTED PROPERTIES OF have been doped with a wide variety of compounds Hg-DOPED p-TYPE IRON OXIDE AS A PH0T0CATH0DE FOR in the past, this is the first time that p-type THE PbjOTOELECTROLYSIS OF WATER USING VISIBLE photoactivity has been observed for FegO^. In our LIGHT1" experiments new preparation procedures and doping with MgO have produced an iron oxide semiconductor Ch. Leygraf, M. Hendewerk, and G. A. Somorjai with reproducible p-type photocurrents. This unique p-type material is used in a p/n diode Stable Mg-doped iron oxides that exhibit assembly as the cathode to reduce hydrogen while p-type character have been synthesized. These connected to a Si-doped iron oxide which acts as have been utilized in the form of sintered poly- the anode. This is the first successful diode crystalline disks for the photodissociation of assembly that employs both p- and n-type poly- water. We report the influence of sintering tem crystalline electrodes to catalytically photo- dissociate water. The dissociation process perature, surface oxygen deficiency, Mg-doping results in evolved hydrogen and oxygen gases (at level, and solution chemistry on the photoactiv a rate of 2 H2 molecules per site per min), which ity of the Mg-doped iron oxide photocathodes. are detectable with a gas chromatograph.

With this diode assembly made from cheap and fBrief version of LBL-14669 and LBL-15269. abundant materials (Fe^, Mg, Si), it may be feasible to extract the hydrogen produced from solar radiation as a storable source of energy, 3. WORK IN PROGRESS if power conversion efficiency (0.05% at present) can be improved. Thin film electrodes of the Mg- and Si-doped iron oxides are being prepared in order to improve the power conversion efficiencies of the p/n diode assembly.

*This work was supported by the Director, Office An electrochemical cell with two compartments of Energy Research, Office of Basic Energy connected by a porous membrane is being construc Sciences, Chemical Sciences Division of the U.S. ted. In this system the pH of the electrolyte Department of Energy under Contract No. solution surrounding the p-type cathode and n- DE-AC03-76SF00098. type anode can then be varied independently. The 130 new cell will interface directly to a UHV chamber LBL Reports for ESCA and other surface analysis measurements. This will permit analysis of the electrode sur 1. Ch. Leygraf, H. Hendewerk, and 6. A. Somorjai, faces following an experiment without exposing "Hg- and Si-Doped Iron Oxides for the Photo- the samples to the atmosphere. catalyzed Production of Hydrogen From Water by Visible Light (2-2 eV < h < 2.7 eV),M to be pub Capacitance and permittivity measurements are lished in J. Catal., LffL-17669. being made to better characterize the p/n diode assembly. Experiments are aimed toward establish 2. Ch. Leygraf, M. Hendewerk, and G. A. Somorjai, ing the carrier concentrations, locate the flat "The Preparation and Selected Properties of band potentials, and determine the permittivity Mg-Doped p-Type Iron Oxide as Photocathode for the constants of the Iron oxides. Photoelectrolysis of Water Using Visible Light," to be published in J. Solid State Chemistry, In other experiments, Auger spectroscopy is LBL-15269. being used to investigate the gradual poisoning of the p-type cathode that occurs in the diode Invited Talks assembly after several hours of operation. Methods of inhibiting the poisoning are also 1. G. A. Somorjai, "Catalyzed Hydrogenation of being investigated. Graphite and CO. Photocatalyzed Surface Proc esses," Fudan University, Shanghai, China, April 10, 1982.

2. G. A. Somorjai, "Photocatalyzed Surface Proc esses," Jilin University, Changchun, China, April 1982 PUBLICATIONS AND REPORTS 23, 1982.

Refereed Journals 3. G. A. Somorjai, "Photodissociation of Water Over Fe-Si-0 Compound Surfaces," 6th DOE Solar 1. C. Leygraf, M. Hendewerk, and G. A. Somorjai, Photochemistry Research Conference, University of "Photodissociatioln of Water by p- and n-Type Colorado, Boulder, Colorado, June 8, 1982. PolycrystalHne Iron Oxides by Using Visible Light (^ 2.7 eV) in the Absence of External 4. G. A. Somorjai, "Hydrogen Production by Potential," Proc. Natl. Acad. Sci. USA, 79^, 5739 Photocatalyzed Reaction on Fe203 Surfaces," (1982); LBL-14494. American Chemical Society, Kansas City, Missouri, September 16, 1982. 2. Ch. Leygraf, M. Hendewerk, and G. A. Somorjai, "Photocatalytic Production of Hydrogen from Water 5. G. A. Somorjai, "The Surface Science of by a p- and n-Type Polycrystalline Iron Oxide Heterogeneous Catalysis and Its Application to Assembly," J. Phy. Che». 85, 4484 (1982); the Photodissociation of Water," Arizona State LBL-14560. University, Tempe, Arizona, November 9, 1982. 131

b. Photochemistry of Materials In the Stratosphere*1 Harold S. Johnston, Investigator

Introduction. The field of stratospheric 1 l 1 photochemistry continues to produce new surprises Cl + HN0 — HCl +NO3 about every two years, and there have been large 3

changes in the predicted effects of nitrogen l5 3 1 1 oxides and of chlorine on stratospheric ozone. k =6.18 xiO" cm molecule" s" During the past year, the calculated effect of 200 0 JJ-*"-- chlorine on the stratospheric ozone column has dropped to the lowest value since the effect was postulated ten years ago; and the calculated effect of nitrogen oxides in reducing ozone is ~~o^ about as large as it was at the conclusion of the 100 Climatic Impact Assessment Program (1974). There is no reason to assume that the present results are final, and active work continues on labora tory studies, atmospheric measurements, and model calculations. t 1 i l 0 0.5 1.0 1.5 2.0 [HN0 ]xlO~16 1. THE REACTION OF CHLORINE ATOMS WITH NITRIC 3 ACID VAPORt Fig. 1.1. Pseudo first-order rate constants for the reaction of atomic chlorine with nitric acid W. J. Marinelli and H. S. Johnston plotted against the concentration of nitric acid for each run. The slope gives the second order The reaction of chlorine atoms with nitric rate constant. Concentrations in units of acid has been presumed to be molecules cur3. (XBL 8012-12918)

CI + HN03 » HCl + N03 served under conditions where a large signal would be expected. The conclusion is that NO3 is not If fast, this reaction would constitute a strong the primary product of the subject -eaction and coupling between chlorine and the oxid&s of nitro the reaction rate is so slow that it is of no gen in the atmosphere, in that an active form of importance in atmospheric chemistry. chlorine {CI) would be rendered inactive (HCl) and an inert form of nitrogen oxides (HNO3) would be converted to catalytically active forms (NO3, N02» NO). This reaction had been previously +Brief version of LBL-13473. studied in two laboratories,*'? but the results at 1. M. Leu and W. B. DeMore, Chem. Phys. Lett. room temperature disagreed by a factor of 300. 41, 121 (1976). It was reinvestigated in this laboratory by the 2. 6. Poulet, G. Lebras, and J. Combourieu, J, methou of laser flash photolysis and vacuum ultra Chem. Phys. 60, 767 (1978). violet resonance fluorescence. Molecular chlorine was photolyzed by a fast (10 ns) laser pulse at 2. TEMPERATURE-DEPENDENT ULTRAVIOLET ABSORPTION 350 nm wavelength, and the disappearance of chlo SPECTRUM OF DI-NITROGEN PENTOXIDE+ rine atoms was followed by its resonance fluores cence at 138.0 and 139.0 nm. During the course of one run with nitric acid in excess, the chlo Francis Yao, Ivan Wilson, and H. S. Johnston rine atoms decayed by a pseudo first-order reac tion fq = K2EHN03J. After a series of runs with Vertical profiles and total vertical columns different nitric acid concentrations, a plot of of nitrogen dioxide have been measured at enough latitudes that one can estimate the global dis the pseudo. first-order constant against the nitric 1 acid concentration gives the desired second order tribution of stratospheric nitrogen dioxide. rate constant, Fig. 1.1. The results found here An anomalous effect called the "Noxon Cliff" has agreed closely with Ref. 1, but disagreed with been observed,2 in which the vertical column of Ref. 2. In another experiment the reaction was nitrogen dioxide decreases dramatically between initiated by passing the laser pulse at 350 nm 45 and 55° latitude in the winter. This sharp down a long tube, and an argon-ion excitea dye decrease of nitrogen dioxide could not be repro laser at 662 nm was co-axially passed down the duced by recent dynamic and chemical models of same tube in order to measure the build up of the ti.? atmosphere. The ultraviolet absorption spec presumed product NO3. However, no NO3 was ob- trum of ai-nitrogen pentoxide was investigated here between 223 and 300 K and between 200 and 380 nm. These measurements involve simple physics but complicated chemistry. Di-nitrogen pentoxide is thermally unstable and reacts strongly even *This work was supported by the Director, Office with bound water on surfaces; and the reaction of Energy Research, Office of Basic Energy products, NO2 and HNO3, absorb ultraviolet radia Sciences, Chemical Sciences Division of the U.S. tion in the same spectral region as N2O5. The Department of Energy under Contract No. spectrum was found to be strongly temperature de pendent, Fig. 2.1. When this temperature depend- DE-AC03-76SFG0098. 732 T/K this laboratory it has been found that the absorp ,„.ig 300 275 250 225 tion cross sections of oxygen in the Herzberg con 10 l3r ; 1 1 r— tinuum has a pronounced temperature dependence. Future Plans. Experiments are being designed to study the photochemistry of molecular nitrogen in the 6 to 12 eV energy range, with an emphasis on the production of the atomic excited electronic

states 2j)an( j 2p as we-ji as ground state ^S and molecular and atomic ions. The Advanced Light Source being planned in the Lawrence Berkeley Laboratory appears to be uniquely suitable for high resolution spectroscopy and cross sections in this spectral region.

1982 PUBLICATIONS AND REPORTS Refereed Journals 1. W. J. Harinelli, D. H. Swanson, and H. S. Johnston, "Absorption Cross Sections and Line Shape for the NOitO-O) Band," J. Chf.m. Phys. /6, 2864 (1982); LBL-13699. ~~ 2. W. J. Marlnelli and H. S. Jonnston, "Reaction Rates of Hydoxyl Radical with NHric Acid and with Hydrogen Peroxide," d. Chen. Phys. 77, 1225 (1982); L3L-24293. "" 3. F. Yao, I. Wilson, and H. S. Johnston, "Temperature-Dependent Ultraviolet Absorption Fig. 2.1. Temperature dependence of the N2O5 Spectrum for Oinitrogen Pentoxide," J. Phys. cross sections at wavelengths between 290 and 380 Chem. 86, 3611 (1982); LBL-14340. nm. The temperature dependence is very weak or absent below 280 nm. (XBL 831-7667) 4. W. J. Marinelli and H. S. Johnston, "Quantum Yield for NO3 Production from Photolysis of C10N0 ," Chem. Phys. Lett. 93, 127 (1982); LBL-149602 . ~~ ence is incorporated in the stratospheric models, most of "Noxon's Cliff" is accounted for.3 LBL Reports * * * 1. J. R. Podolske and H. S. Johnston, "The Rate of the Resonant Energy-Transfer Reaction Between +Bn"ef version of LBL-14340. 0 (1Ag) and H00," LBL-14961. 1. S. Solomon, H. S. Johnston, M. Kowalczyk, and 2 1. Wilson, Pure and Applied Geophysics 118, 58 Other Publications (1980). 2. J. F. Noxon, J. Geophys. Res. 84, 5067 (1979); 1. H. S. Johnston, "Odd Nitrogen Processes," 85, 4560 (1980). Chapter 4 in Stratospheric 02one and Man, Volume 17 S. Solomon, private communication (1982). I, edited by F. A. Bower and R. B. Ward, CRC Press, Inc., Boca Raton, Florida, 1982, p. 87-140; LBL-10585. 3. WORK IN PROGRESS Invited Talks A diode laser is being developed to measure free radical intermediates in photochemical reac 1. P. S. Connell, F. Magnotta, D. Swanson, and tions at very high resolution in the infrared H. S. Johnston, "Product Identification and Quan- spectral region. By the method of laser flash tum Yield Determination in N2O5 Photolysis at photolysis and resonance fluorescence, the primary Several Discrete Wavelengths Between 249 and 300 products of N2O5 photolysis are being studied over nm," International Photochemical Symposium, a wide range of conditions. Also, the fluores Stanford University, Palo Alto, California, June cence of the nitrate free radical NO3 is being 1982, Extended Abstract, based on LBL-9034 and investigated in a large cell at low pressure. In LBL-9981. 133 2. Chemical Physics

a. Energy Transfer and Structural Studies of Molecules on Surfaces* Charles B. Harris, investigator

Introduction. A proper description of the This is interpreted as enhanced multiphoton ways in which internal excitation energy is absorption by adsorbed molecules because of transferred between molecules and surfaces enhanced surface fields at the silver surface, through electromagnetic field interactions, followed by fragmentation of the excited mole particularly at short distances, is crucial to cules out of photoionized three-photon states. the understanding of a wide variety of molecule- The enhanced multiphoton absorption is presumably surface interactions. The validity of a classi due to Mie resonances associated with silver cal point dipole model for the transfer of energy spheres thut form when single crystal Ag(lll) and between electronically excited molecules and Ag(llO) ars Ar-ion sputtered under UHV conditions. metal surfaces is now generally accepted. The simplicity of this model and the physical insight it provides into the mechanisms of the energy ' Brief version of J. Chem. Phys. 77{7), 3767 transfer make it attractive for use in many (1982). ~~ classes of problems. In the past year, the first experiments on a GaAs(llO) surface have been completed which demonstrated that the model is 2. ELECTRONIC ENERGY TRANSFER TO SEMICONDUCTOR also valid to very short (~10 A) distances above intrinsic semiconductor surfaces. In addition to SURFACE:t the work on GaAs, a series of experiments on sur face enhanced photochemistry on silver have been C. B. Harris, A. P. Alivisatos, and P. M. Whitmore initiated. The observations can be interpreted as enhanced multiphoton absorption by adsorbed The fir«t experimental and theoretical molecules because of the enhanced electromagnetic investigation of electronic energy transfer from laser fields at the surface, followed by fragmen a molecule to the surface of an intrinsic semi tation of the excited molecules out of photo- conductor, gallium arsenide (110), was completed. ionized three photon states. The system chosen for this initial investi gation was triplet nn* or 1,4 diazabenzene on GaAs(llO). The molecular emission occurs at 3800 A {3.3 eV) and coincides with a large ab 1. ENHANCED PHOTOCHEMISTRY ON METAL SURFACES7 sorption in the gallium arsenide because of the A3-A1 interband transition. C. B. Harris, G. M. Goncher, and C. A. Parsons Figure 1.1a shows the observed distance The observation of photochemistry on metal dependence of the emission lifetime compared to surfaces depends on the relative rates of photo- the predictions of a classical local dielectric excitation by the incident radiation and de- response theory. The model reproduces, within excitation by energy transfer to metal and experimental error, the functional dependence of surface modes. Rapid quenching of the lowest the lifetime within the molecule-semiconductor excited states is expected on metal surfaces; separations shown. The success of the theory however, excited electronic states reached by suggests that the dominant mechanisms for energy even-multiphoton processes can exhibit much transfer to the GaAs surface are included in the longer lifetimes near a surface than the dipole local (optical) dielectric constant. Calcula allowed one-photon transitions. When the multi tions of the wavevector dependence of the energy photon absorption for molecules near surfaces is transfer rate (i.e., the contribution of each of enhanced (E4 for two-photon processes, E6 for the different wavevector components of the dipole three-photon processes), photoreactions from field to the energy transfer), show (cf. Fig. these states are easily observable with low power 1.1b) that almost all of the energy is trans lasers (<50 mW/cm2). ferred through the high wavevector components of the dipole near field, generating electron-hole pairs in GaAs via non-vertical transitions. The photochemistry on silver sliows a nonlinear dependence on incident intensity, and decreases sharply as the surface plasmon energy is approached. TBrief version of LBL-15638.

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. 134

*",—-H *Brief version of References 1-1. 'This research is not supported by DOE operating funds. However, DOE equipment was used in the experiments. 1. LBL-15640. 2. Picosecond Phenomena III edited by K. B. Eisenthal, R. M. Hochstrasser, H. Kaiser, and A. Laubereau, Springer Series in Chemical Physics sn ir*l,4-diazobenzene 23, 196 (1982). above GaAs(IIO) TT LBL-15639. 4. J. Chem. Phys. 77(9), 4781 (1982).

100 SMMONIA THICKNESS (A) 1982 PUBLICATIONS AND REPORTS

Refereed Journals \ nw 1,4-diazabenzene 0.8 1. H. 0. Robota, P. H. whitmore, and C. B. - \PAIR PRODUCTION Harris, "Optical Properties of Molecules Chemi- \ PHOTONS^ • sorbed on the Ni(lll) Surface," J. Chem. Phys. 0.6 76(4), 1692 (1982); LBL-1183?.

2. P. H. Whitmore, H. J. Robota, and C. B. 0-» Harris, "Electronic Energy Transfer from Pyrazine /S( -^fOLARITONS to a Silver(lll) Surface Between 10 A and 400 A," J. Chem. Phys. Communication 76, 740 (1982); 0.2 LBl-13031. ~

+ ' 1 1 —- ll 1 3. S. M. George, A. L. Harris, M. Berg, and O 100 200 300 400 500 C. B. Harris, "The Temperature Dependence of SPACER THICKNESS (8) Homogeneous and Inhomogeneous Vibrational Line- width Broadening Studies Using Coherent Pico Fig. 1.1. (a) Logarithm plot of the lifetime second Stokes Scattering," in Picosecond of the3 nTi* state of 1,4-diazabenzene above Phenomena III edited by K. B. Eisenthal, R. H. GaAs(llO) vs ammonia spacer thickness. The Hochstrasser, W. Kaiser, and A. Laubereau, points are experimental values, and the solid Springer Series in Chemical Physics 23, 196 curve is the behavior calculated from a classical (1982), (Springer-Verlag, Berlin, He'idelberg and dielectric response model for the GaAs surface, New York); LBL-15637. (b) Calculated decay probability vs distance for 3nn*l,4-diazabenzene on an ammonia spacer over 4. P. H. Whitmore, H. J. Robota, and C. B, GaAs(llO). (XBL 831-5167) Harris, "Mechanisms for Electronic Energy Trans fer Between Molecules and Metal Surfaces; A Comparison of Silver and Nickel," J. Chem. Phys. 27(3), 1560 (1982); LBL-13780. VIBRATIONAL COHERENCE AND PICOSECOND STUDIES LIQUIDS+* t5. S. M. George and C. B. Harris, "Dependence of Inhomogeneous Vibrational Linewidth Broadening on C. B. Harris, D. Ben-Amotz, M. Berg, S. M. George, Attractive Forces from Local Liquid Number Densi and A. L. Harris ties," 0. Chem. Phys. Notes 77(9), 4781 (1982).

Recently a general theory for transient 6. G. M. Goncher and C. B. Harris, "Enhanced stimulated Raman scattering, including high laser Photofragmentation on a Silver Surface," J. Chem. 1 depletion, has been completed. This theory was Phys. Communication 7_7(7), 3767 (1982); LBL-14540. motivated by the discovery2.3 that the assump tion of low laser depletion is not justified in LBL Reports coherent picosecond Raman studies of liquids. 1. P. M. Whitmore, "Electronic Energy Transfer Using the effects induced by high lasei from Molecules to Metal and Semiconductor Sur depletion into a vibrational ensemble and its faces, and Chemisorption-Induced Changes in theoretical understanding, ultrashort vibrational Optical Response of the Nickel(111) Surface," dynamics in liquids can be studied. In particu Ph.D. thesis, LBL-15092. lar the attractive and repulsive contributions to vibrational linewidth broadening can be ext>-ri- 1 2. A. P. Alivisatos and C. B. Harris, "Electronic mentally separated ' and used to test various Energy Transfer to Semiconductor Surfaces: 3nir* theories for liquids. Pyrazine/GaAs(110)," LBL-15638. 135

+3. S. H. George and C. B. Harris, "Theory for 2. C. B. Harris, "Optical Studies of Chemisorp- Selective Vibrational Dephasing Experiments Using tion and Energy Transfer on Metal Surfaces," Iowa Transient Stimulated Raman Scattering in High State University, Ames, Iowa, April 15, 1982. Laser Depletion," LBL-15640. 3. C. B. Harris, "Use of Nonlinear Optics on a 4. D. Ben-Amotz, S. M. George, and C. B. Harris, Picosecond Timescale to Study the Structure and "Experimental Investigations of High Laser Deple Dynamics of Liquids," Iowa State University, Ames, tion in Transient Stimulated Raman Scattering," Iowa, April 16, 1982. LBL-15639. 4. C. 8. Harris, "The Temperature Dependence of 5. S. M. George and C. B. Harris, "Picosecond Homogeneous and Inhomogeneous Vibrational Line- Studies of the Temperature-Dependent Homogeneous width Broadening Studies Using Coherent Pico and Inhomogeneous Vibrational Linewidth Broaden second Scattering," Third Topical Meeting on ing in Acetonitrile," LBL-15641. Picosecond Phenomena, Garmisch, Partenkirchen, W. Germany, June 16-18, 1982.

5. C. 8. Harris, "Surface Enhanced Photo Invited Talks chemistry," Emil Warburg Symposium on Unconven tional Solids, Munich, Germany, June 27 - July 1, 1. C. B. Harris, "Optical Studies of Chemisorp- 1982. tion and Energy Transfer on Metal Surfaces," * * * University of Texas at Austin, April 13, 1982. "^Supported by National Science Foundation. 136 b. Molecular Beam Spectroscopy* John S. Winn, Investigator

Introduction. The purpose of this work is to use spectroscopic probes of molecules isolated in * * * a molecular beam environment to elucidate molecu +Brief version of LBL-14690; J. Pfcys. Chem. 87, lar mechanisms of fundamental importance to chem 265 (1983). ~ ical reaction processes. Often the fate of a ^Present address: Dartmouth College, Hanover, NH complex chemical environment is determined by the 03755. elementary steps which initiate a reaction. New 5Present address: IBM, Burlington, VT. understanding of such processes and better con ^Present address: Columbia University, New York, trol over them are complementary goals of this wr. research. 'Present address: Jackson State University, Jacksrn, MS.

J. DISSOCIATION MECHANISMS OF METAL CARBONYLS* 2. SUPERSONIC MOLECULAR BEAM RELAXATION John S. Winn,4 David V. Horak,5 William E. MECHANISMS** Hollingsworth,11 and Brian C. Hale" John S. Winn,§ Henry S. Luftman,11 Michael Maier," Metal carbonyl compounds constitute an attrac and Susan A. Sherrow tive class of compounds for the facile transport of chemically reactive metal atoms in the gas A gas at equilibrium is well understood to phase. Chemically saturated carbonyls are rela have various modes of internal and translational tively stable and easily prepared compounds char energy distributed in a simple way characterized acterized by a volatility that is typically fifty by a single parameter, the equilibrium tempera orders of magnitude greater than that of the par ture. Radically nonequilibrium flow situations, ent bulk metal. Past studies have demonstrated however, are of great practical importance in de that these compounds can serve as catalysts in vices such as chemical lasers and jet propulsion many important reactions and that dissociation of engines. These situations are sufficiently com the compounds themselves can lead to thin, highly plex to be incompletely understood at a molecular reactive, metal films. level.

To elucidate the first steps in these proc It has been known for some time that a super esses, the molecular dynamics of the dissociation sonic molecular beam is characterized by a very of isolated carbonyls have been studied using narrow translational energy spread about a mean metastable atom impact, electron impact, vacuum value with internal molecular energies that are ultraviolet photolysis, and near UV photolysis. highly relaxed. What has not been widely apprec These sources have enough p*cvgy to dissociate iated or recognized is that these flow distribu carbonyls to the bare metal atom and the stoichi tions, translational and internal, are highly ometric number of CO liganos. Atomic fluorescence coupled. By combining a time-of-flight measure follows, and the main clue to the mechanism lies ment of the translational energy distribution to in the analysis of this fluorescence. s molecular beam electric resonance spectrometer's velocity-selective probe of the rotational energy Each of these energy sources produces dissoci distribution, one can detect and analyze this ation in a similar way. The atomic states indi coupling. cate that a restricted statistical distribution of energy occurs on dissociation, implying a vir One finds that molecules moving at a velocity tually simultaneous release of all ^0 ligands. near the median are characterized by a rotational The photolysis and electron impact experiments distribution that is more highly relaxed than the yield spin-selected atoms, while metastable atom distribution characteristic of the velocity aver electronic energy transfer experiments show no aged ensemble or the molecules moving far from spin selectivity. One can now predict the dis the median velocity. The molecular scattering sociation pathways of metal carbonyls under vir mechanism that produces such coupled distribu tually any conditions. tions remains to be elucidated.

*Th1s work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. 137 * * * Laser-Assisted Excitive Penning Ionization," Ph.D. thesis, LBL-14278. tBrief version of LBL-15091. •Supported in part by the National Science 2. 0. V. Horak, "Analysis of Iron Fluorescence Foundation. from Vacuum Ultraviolet Photolysis of Iron Penta- 'Present address: Dartmouth College, Hanover, NH carbonyl," Ph.D. thesis, LBL-14612. 03755. "Present address: University of Texas, Austin, 3. D. V. Horak and J. S. Winn, "Fe* Emission

TX.' Yield and Photoionization of Fe(C0)5 by VUV "Present address: IBM, San Jose, CA. Radiation," LBL-14690.

4. H. S. Luftman, "Supersonic Molecular Beam 1982 PUBLICATIONS AND REPORTS Electric Resonance Spectroscopy and van der Waals Molecules," Ph.O. thesis, LBL-15091. LBL Reports 5. W. E. Hollingsworth, "Metal Atom Fluorescence 1. J. H. Goble, Jr., "Inversion of the Potential from the Quenching of Metastable Rare Gases by Function of Weakly Bound Diatomic Molecules and Metal Carbonyls," Ph.D. thesis, LBL-14917. 138

c. Selective Photochemistry*

C. Bradley Moore, Investigator

I. ABSOLUTE RATE CONSTANTS FOR THE REMOVAL OF ranging from He to i-C^g using the technique of

CH2 (lAi) laser photolysis/cw laser resonance absorption.1 Absolute rate constants for CH2 (*Ai) removal Andrew 0. Langford, Hrvoje Petek, and C. Bradley by NO, C2H6» C3H8, C2H4, i-C^s, and CHgCO were Moore measured for the first time. These processes were found to occur with nearly every collision. Despite the importance of methylene as an Measured rates of CHg (*Ai) removal by He, Ar, Kr, intermediate in the oxidationof acetylene and N2, CO and H2 are in good agreement with other other hydrocarbons, accurate rate constants direct measurements recently reported in the lit necessary for modeling studies have been lacking. erature,2 but are approximately one order of This state of affairs stems from the existence of magnitude faster than rate constant values previ two low-lying electronic states that differ sig ously used for modeling.3 These rates, which nificantly in structure and reactivity. Absolute include contributions from both reaction and rate constants for the short-lived singlet first intersystem crossing to the ground state, are excited state (^Aj) are particularly uncertain. shown in Table 1.1.

We have recently completed a study of CHj> Absolute rate constants for the removal of {lAi) removal by a series of collision partners vibrationally excited CH2 (*Ai) by He, Ar, and

(cm3 molec-1 s~l).

Ref. 2

He 3.1 ± 0.3

Ne 4.2 ± 0.6

Ar 5. .8 * 0.5 6.0 ± 0.5 0.67 ± 0.13

Kr 7. 9 * 0.6 7.0 ± 0.6 Xe 16 ±2

N2 11 * 1 8.8 ± 0.3 CO 49 * 4 56 ±6 °2 74 ± 5 30 M NO 160 ± 15

105 * 5 130 ± 10 7.0 * 1.5

-n4 70 * 4 73 ±6 3.5 ± 1.0 C-H,, 190 * 20

240 ± 20

150 * 60 >-2"4 1-C„H„ 225 ± 20

270 ± 20

sight into the requirements for mode selective chemistry can be obtained by studying unimolec-

ular reactions.* /\ cw dye laser was used to induce the isomerizations of cyclobutene and 1-cyclopropylcyclobutene to the corresponding l,3-butadiene5

In the vibrational overtone spectra of these molecules (v = 5 and v = 6), inequivalent hydro gens absorb at different frequencies. Visible photons selectively excise the different CH oscillators, thereby depositing a known amount of energy directly into vibrational degrees of free dom of the molecule in its electronic ground state in a single photon absorption. Values of the unimolecular isomerization rate constant, k(E), depend on the total energy and do not show any observable dependence on the type of CH over tone transition excited (Fig. 2.1). These results are consistent with RRKM theory on timescales of several ps and 100 ps for 1-cyclopropyl- cyciobutene and cyclobutene, respectively, which Quenching Gas Pressure (Torr) may imply that either the CH oscillator excited

Fig. 1.1. Pseudo-first-order decay rates for the (0,1,0) and (0,0,0) vibrational levels of CH 2 IU.U —r- 1 > 1 ' ' (Mi) as a function of added He (A,A) and Ar v = 6, olefin!" %d. (O.*). The CH2CO pressures ?"e 0.300 torr for 8.0 - the (0,1,0) decays and 0.200 for the (0,0,0) de 6.0 cays. The solid lines correspond to the (0,0,0) - rate constants from Table 1.1. The vibrational^ v = 6, methylenic V / excited molecule undergoes singlet-tripU.. trans 4.0 fer at the same rate as vibrational ground state. / (XBL 832-8066) / / / / / s CH2CO have also been measured for the first time. 2.0 - / / These rates were found to be identical to the / / ground state rates for both rare gases, where the r S / only channel is intersystem crossing, and for / / / / ketene where reaction is the primary channel / / 1.0 (Fig. 1.1). The experimental approach is cur f v = 5 /' ~ rently beinq extended to permit studies of ground 0.8 • olefimc / state CH2 (3Bx) kinetics in the infrared. The T / relative importance of reaction and intersystem 0.6 / crossing in the present measurements can then be evaluated. •V / 0.4 , 5,/ methylenic Brief version of LBL-15666, submitted to J. / / Chem, Phys. / 1. A. 0. Langford, H. Petek, and C. B. Moore, 0.2 / submitted to J. Chem. Phys. / ,'. M. N. R. Ashfold, M. A. Fullstone, G. Hancock, / ind G. W. Ketley, Chem. Phys. 5_5_, 245 (1981). 3. W. Braun, A. M. Bass, and M. J. Pilling, J. Chem. Phys. 52, 5131 (1970). 0 1 1 1 l , l 13500 14500 15500 16500 2. HIGH VIBRATIONAL OVERTONE PHOTOCHEMISTRY E (cm"') Joseph M. Jasinski, Joan K. Frisoli, and Fig. 2.1. Plot of experimental values of k(E) vs C. Bradley Moore E for cyclobutene. The dotted and solid lines are results of two different RRKM calculations. A better understanding of the behavior of E has been defined as the photon energy plus the highly vibrational1y excited molecules and in- average thermal energy. (XBL 832-8067) 140

is not strongly coupled to the reaction coordi 5. C. Bradley Moore, "High Resolution Laser nate* or that energy deposited in a particular Spectroscopy of Small Molecules," Thirteenth bond is randomized on these timescales. Australian Spectroscopy Conference, Australian Academy of Science, Melbourne, Australia, and La Trobe University, Bundoora, Australia, August 16, 1982. 1. C. F. Moore and I, W. M. Smith, Faraday Discussion, Chem. Soc. ,67, 173 (1979). 6. C. Bradley Moore, "Laser Photochemistry," Royal Australian Chemical Institute 7th National Convention of the Physical Chemistry Division, Canberra, Australia, August 26, 1982.

1982 PUBLICATIONS AND REPORTS 7. C. Bradley Moore, "Vibrational Relaxation of Small Molecules in Solid Rare Gas Matrices," Refereed Journals Physical Chemistry Seminar, Department of Chemistry, University of California, Berkeley, 1. J. S. Wong, R. A. McPhail, C. B. Moore, and September 22, 1982. H. L. Strauss, "Local Mode Spectra of Inequivalent C-H Oscillators in Cycloalkanes and Cycloalkenes," 8. C. Bradley Moore, "Vibrational Energy Transfer J. Chem. Phys. 86, 1478 (1982); LBL-13442. in Matrices; CH3F, HCN, and NCI (v = 1,2 and 3) in Ar, Kr, and Xe," American Chemical Society 2. L. Young and C. B. Moore, "Vibrational National Meeting, Kansas City, Missouri, Septem Relaxation of CH3F in Inert Gas Matrices," J. ber 16, 1982. Chem. Phys. 79, 5869 (1982); LBL-13871. 9. C. Bradley Moore, "Photophysics and Photo 3. J. S. Wong and C. B. Moore, "Inequivalent C-H chemistry of Formaldehyde," Charles F. Hutchison Oscillators of Gaseous Alkanes and Alkenes in Distinguished Lecturer, Department of Chemistry, Laser Photoacoustic Overtone Spectroscopy," 0. University of Rochester, Rochester, New York, Chem. Phys. 2Z» 603 (1982); LBL-13872. November 1, 1982.

10. C. Bradley Moore, "The Chemistry and Invited Talks Spectroscopy of Highly Vibrationally Excited Molecules," Charles F. Hutchison Distinguished 1. C. Bradley Moore, "Laser Chemical Kinetics: Lecturer, Department of Chemistry, University of State Selected and Thermal," University of Rochester, Rochester, New York, November 2, 1982. Colorado, Boulder, Colorado, Department of Chem istry, February 15, 1982. 11. C. Bradley Moore, "Vibrational Relaxation of Small Molecules in Solid Rare Gas Matrices," 2. C. Bradley Moore, "Dynamics and Photochemistry Charles F. Hutchison Distinguished Lecturer, of ghly vibrationally Excited Small Molecules," r Department of Chemistry, University of Rochester, P'.""r Chemistry Award Symposium, American Chemical Rochester, New York, November 3, 1982. cjciety National Meeting, Las Vegas, Nevada, March 31, 1982. 12. C. Bradley Moore, "Laser Photochemistry," Department of Chemistry Colloquium, Yale Univer 3. C. Bradley Moore, "Reaction Rate Measurements sity, New Haven, Connecticut, November 5, 1982. by Sensitized Laser Pyrolysis," Avro Everett Re search laboratory, Everett, Massachusetts, May 5, 1982. LBL Reports

4. C. Bradley Moore, "High Overtone Spectroscopy 1. A. 0. Langford, H. Petek, and C. B. Moore, and Vibrational Photochemistry," Los Alamos "Collisioi.al Removal of CH2 (^1): Absolute Rate Scientific Laboratory, Los Alamos, New Mexico, Constants for Atomic and Molec-lar Collision May 13, 1982. Partners at 295 K," LBL-15666. 141

d. Physical Chemistry with Emphasis on Thermodynamic Properties*

Kenneth S. Pitzer, Investigator

Introduction. The general objective is the duced at the CI stage along with the electron discovery and development of methods of calcula repulsion integrals. The results are thus valid tion of thermodynamic and related properties of regardless of the magnitude of the spin-orbit important chsmical systems by use of quantum and terms. statistical mechanics together with experimental measurements for key systems. Recently, an ab Calculations were made for five excited states initio relativistic quantum mechanical procedure as well as the ground state of TlH. The calcu was developed which yields, for molecules con lated potential curves agree very well with the taining very heavy atoms, results of comparable experimental curves for both the ground and first accuracy to that attained by others for light excited 0+ states. The latter has a very pecul rr,iecules. This major advance allows the calcu iar shape that is correctly calculated. There lation of energies, bond distances, and other are also a few incompletely interpreted spectral properties nf the ground and excited states of features at higher energy for which & satisfac molecules, and model surface structures contain tory explanation is now available from these ing very heavy atoms where the conventional non- calculations. Predictions are made concerning relativistic methods are inadequate. Such several unobserved states. The complete array of results are important in understanding surface potential curves is shown in Fig, 1.1. and catalytic properties and in evaluation of possible laser systems.

Other areas of recent interest include appli tBrief version of J. Chem. Phys. 76_, 5087 (1982); cations of advanced symmetry theory to chemical LBL-13799. problems and the statistical mechanics of ionized ^Present address: Department of Chemistry, systems—plasmas as well ss electrolyte solutions. Clarkson College of Technology, Potsdam, NY 13676.

Some related research applying the earlier results of this project to geochemical problems is supported by DOE through the Division of Earth Sciences at LBL and is discussed in Annual Report of that Division.

1. RELATIVISTIC A8 INITIO MOLECULAR STRUCTURE CALCULATIONS INCLUOING CONFIGURATION INTERACTION WITH APPLICATION TO SIX STATES OF T1H+

Phillip A. Christiansen, K. Balasubramanian, and Kenneth S. Pitzer

This article represents the first application of a major advance in method of relativistic electron structure calculations that was reported last year. This method makes it feasibl to in clude all relativistic effects in ab init^ calculations with the extensive coTifiguration in teraction (CI) required to account for electron correlation. T1H was chosen because of the large spin-orbit effect of the 6p orbital of Tl which R (botir) is important for the bond to H. Fig. 1.1. Computed bonding curves for the two Several new computer codes were required but lowest 0+ and 1 states and the lowest 0~ and 2 the basic mathematics was available to execute states of TlH. The dashed curves at large R are this program in which the spin-orbit operator is estimates. (XBL 831-7976) obtained from the difference in effective poten tials for j = 1 + 1/2 and j = 1 - 1/2 for a given 1 together with appropriate projection operators. 2. ELECTRON STRUCTURE CALCULATIONS INCLUDING CI

The calculation is initiated in A-S coupling at FOR TEN LOW LYING STATES OF Pbj and Sn2. the SCF stage. The spin-orbit terms are intro PARTITION FUNCTION AND DISSOCIATION ENERGY OF T Sn2

K. Balasub'-amanian and Kenneth S. Pitzer •This work was supported by the Director, Office of Energy Research, Office of Basic Energy As a next stage of increased complexity after Sciences, Chemical Sciences Division of the U.S. TlH, the molecules Pbi and Sng were selected for Department of Energy under Contract No. relativistic electron structure calculations. DE-AC03-76SF00098. These molecules have twice the number of valence 142

electrons; they have also received considerable closely spaced numbers do not correspond to the recent attention in experimental spectroscopic observed spectra. This discrepancy is because of investigations. some combination of noise in the spectra, rota tional perturbations, and insufficient resolution. The calculational method was essentially the Spectra of laser diode resolution should have the same as for the T1H, but with the additional bond predicted intensity ratios. Such an agreement ing electrons the computational limits would have was observed in SFg. been exceeded without some further approximations. These approximations were not fundamental, how * * * ever, and it was possible to show that omitted terms were really unimportant. Vief version of J. Mol. Spectr. 93, 447 (1982); LBL-13826. A number of very interesting features emerged 1. Other reports from this research area: in this work. The large spin-orbit coupling in LBL-12644, LBL-12645, LBL-12724, LBL-14437, Pbg yields a pattern of quantum states quite LBL-14548, and LBL-14598. different from that of Sng and the lighter fourth group molecules. Of the ten states calculated, 1982 PUBLICATIONS AND REPORTS only three had been definitely identified in the experimental spectra of Pb2 and even less was Refereed Journals definitely known for Sn2- The present results made possible the interpretation of several more 1. Kenneth S. Pitzer, "The Treatment of Ionic experimental spectral features for each molecule Solutions Over the Entire Miscibility Range," and predict uninvestigated spectral regions where Ber. Bunsenges, Phys. Chem. 85, 952 (1982); bands should be found. For Sn2 there are several LBL-12761. other states within thermal range of the ground state that must be included for accurate inter 2. K. Balasubramanian, "The Symmetry Groups of pretation of the mass spectrometric measurements Chemical Graphs," Int. J. Quantum Chem. 21, 411 of the dissociation energy. These data were (1982); LBL-12762. ~ reinterpreted on the basis of the present theo retical results; the revised DQ is 2.04 ± 3. K. Balasubramanian, "Spectra of Chemical 0.01 eV. Trees," Int. J. Quantum Chem. 21, 581 (1982); LBL-13001. ~"

4. K. Balasubramanian, "An Algorithm for the Generation of Nuclear Spin Species and Nuclear +Br1ef version of J. Phys. Chem. 86, 3068 (1982), Spin Statistical Weights," J. Comput. Chem. 3, 69 LBL-14418; J. Chem. Phys. 78. 32111983); (1982); LBL-12644. LBL-14723. 5. K. Balasubramanian, "Computer Generation of 3. NUCLEAR SPIN STATISTICS OF CUBANE AND Nuclear Spin Species and Statistical Weights of 1C0SAHEDRAL B0R0HYDRI0E IONS* Rovibronic Levels," J. Comput. Chem. 3, 75 (1982); LBL-12645. K. Balasubramaniar- Kenneth S. Pitzer, and Herbert L. Strauss 6. Phillip A. Christiansen and Kenneth S. Pitzer, "Reliable Static Electric Dipole Polar- Nuclear spin statistical weights for the izabilities for Heavy Elements," Chem. Phys. rovibronic levels of molecules are of consider Lett. 85, 434 (1982); LBL-13256. able interest since they provide for intensity ratios of rotational lines. The nuclear spin 7. Pamela S. Z. Rogers, Daniel J. Bradley, and statistical weights of molecules with very high Kenneth S. Pitzer, "Densities of Aqueous Sodium symmetry such as cubane and icosahedral boro- H - are Chloride Solutions from 75 to 200°C at 20 Bar," hydride ions (B^2 12 ^) neither readily 0. Chem. & Eng. Data 27, 47 (1982); LBL-12407. available nor c^y to obtain. Recent experi mental interest in the vibrational spectra of cubane motivated us to investigate the nuclear 8. K. Balasubramanian, Herbert |_. Strauss, and spin statistics of these two structures. Kenneth S. Pitzer, "Nuclear Spin Statistics of Cubane and Icosahedral Borohydride Ions," J. Molec. Spectros. 93, 447 (1982); LBL-13826. We have used the group theoretical-generating- function method and the subsequent computer pro 9. Phillip A. Christiansen, K. Balasubramanian, grams developed in this program as reported last and Kenneth S. Pitzer, "Relativistic Ab Initio year. These programs need generalized character Molecular Structure Calculations Inclining Con cycle indices (GCCI's), which can be obtained figuration Interaction with Application to Six easily for rigid molecules from their character States of T1H," J. Chem. Phys. 76, 5087 (1982); tables. Several other applications of operator LBL-13799. ~~ methods and GCCI's can also ba found in addition al LBL reports.1 10. K. Balasubra.nanian, "Computer Generation of rsomers," Computers & Chemistry 6, 57 (1982); A comparison between the statistical weights LBL-13692. and observed spectra was attempted for the P- branch bands of the 852 cm-1 vibration of cubane. 11. K. Balasubramanian, "Computer-Assisted Enum The spin weights are 667 for J = 30, 665 for J = eration of NMR Signals," J. Mag. Res. 48, 165 31, 695 for J = 32, 715 for J = 33, etc. These (1982); LBL-13693. — 143

+12. J. Christopher Peiper and Kenneth S. Pitzer, 7. Kenneth S. Pitzer, "The Thermodynamics of "Thermodynamics of Aqueous Carbonate Solutions Unsymmetrical Electrolyte Mixtures: Enthalpy and Including Mixtures of Sodium Carbonate, Bicarbo Heat Capacity," LBL-15318. nate, and Chloride," J. Chem. Thermodynamics 14, 613 (1982); LBL-12725. ^8. M. Conceic,ao P. de Lima and Kenneth S. Pitzer, "Thermodynamics of Saturated Aqueous 13. P. S. Z. Rogers and Kenneth S. Pitzer, Solutions Including Mixtures of NaCl, KC1, and "Volumetric Properties of Aqueous Sodium Chloride CsCl," LBL-15301. Solutions," J. of Phys. and Chem. Ref. Data, 11, 15 (1982); LBL-12414. '9. Rabindra N. Roy, James J. Gibbons, J. C. Peiper, and Kenneth S. Pitzer, "Thermodynamics of 14. Kenneth S. Pitzer and K. Balasubramanian, the Unsymmetrical Mixed Electrolytes HCl-LaCl3," "Properties of Ten Electronic States of Pb2 from LBL-15319. Relativistic Quantum Calculations," J. Phys. Chem. .86, 3068 (1982); LBL-14418. f10. R. C. Phutela and Kenneth S. Pitzer, "Thermodynamics of Aqueous Calcium Chloride, 15. K. Balasubramanian, "Method for Constructing LBL-15322. Isomerization Reactions," Int. J. Quantum Chem. 22, 385 (1982); LBL-12809. til. M. Conceicao P. de Lima and Kenneth S. Pitzer, "Thermodynamics of Saturated Electrolyte 16. K. Baiasubramanian and M. Randic, Mixtures of NaCl with Na2S04 and with MgCl2, "Characteristic Polynomials of Structures with Pending Bonds," Theor. Chim. Acta, 61, 307 LBL-15323. (1982); LBL-13694. 12. K. Balasubramanian, "Computer Generation of the Symmetry Elements of Non-Rigid Molecules," 17. K. Balasubramanian, "Topological and Group LBL-15455. Theoretical Analysis in Dynamic NMR Spectroscopy," J. Phys. Chem. 86, 4668 (1982); LBL-14437. 13. Kenneth S. Pitzer, "Gilbert N. Lewis and the Thermodynamics of Strong Electrolytes," LBL-14214. 18. K. Balasubramanian, "Symmetry Operators of Generalized Wreath Products and Their Applica Other Publications tions to Chemical Physics," Int. J. Quantum Chem. 22, 1013 (1982); LBL-12724. 1. Kenneth S. Pitzer, "Characteristics of Very

+ Concentrated Aqueous Solutions," in Chemistry and 19. Kenneth S. Pitzer and John S. Murdzek, Geochemistry of Solutions at High Temperatures "Thermodynamics of Aqueous Sodium Sulfate," J. and Pressures, edited by David Rickard and Frans Solution Chem. U., 409 (1982); LBL-14522. E. Wickman, Pergamon Press, New York, 1982, ^20. Kenneth S. Pitzer, "Self-Ionization of Water p. 249. at High Temperature and the Thermodynamic Proper 2. Kenneth S. Pitzer, "Thermodynamics of Electro ties of the Ions," J. Phys. Chem. 86, 4704 (1982); lyte Solutions Over the Entire Miscibility Range," LBL-14493. Chapter 26 Chemical Engineering Thermodynamics, edited by S. FY Newma'n, Ann' Arbor Science, LBL Reports Michigan, 1982. 1. Kenneth S. Pitzer, "Relativistic Calculations Invited Talks of Dissociation Energies and Related Properties, LBL-14705. 1. Kenneth S. Pitzer, "Relativistic Calculations of Dissociation Energies and Related Properties," 2. K. Balasubramanian, "Operator and Algebraic Lecture at Symposium on Relativistic Effects in Methods in NMR Spectroscopy. I. Generation of Quantum Chemistry at Ab& Akademi, Finland, June Spin Species," LBL-14548/1. 21-23, 1982.

3. K. Balasubramanian, "Operator and Algebraic 2. K. Balasubramanian, "Group Theory of Non- Methods in NMR Spectroscopy. II. Projection Rigid Molecules and Its Applications," Inter Operators and Spin Functions," LBL-14548/2. national Symposium on Symmetries and Properties of Non-Rigid Molecules, Ecole Normale Superieure 4. K. Balasubramanian, "Non-Rigid Molecular de Jeunes Filles, Montrouge, Paris, France, July Group Theory and Its Applications," LBL-14598. 1982.

5. K. Balasubramanian and Kenneth S. Pitzer, "Electron Structure Calculations Including CI for Ten Luw Lying States of Pb2 and Sng. Partition Function and Dissociation Energy of Sn2," "h"his work was supported by the Director, Office LBL-14723. of Energy Research, Office of Basic Energy Sciences, Division of Engineering, Mathematics, +6. Kenneth S. Pitzer, "The Thermodynamics of and Geosciences of the U.S. Department of Energy Sodium Chloride Solutions in Steam," LBL-14886. under Contract No. DE-ACO3-76SF00O98. 144

e. Molecular Interactions* William A. Lesier, Jr., Investigator

1. THEORETICAL STUDY OF ELEMENTARY REACTIONS IN We used ab initio quantum mechanical methods COMBUSTION PROCESSES* to study the elementary reactions outlined above. In many bond-breaking and bond-formation proc M. Dupuis, W. A. Lester, Jr. T. Takada, and esses, the Hartree-Fock (HF) model breaks down. J. J. Wendoloski In such cases a multiconfiguration Hartree-Fock (MCHF) wavefunction can provide a qualitatively The reaction of oxygen atoms with olefins correct description of the reaction mechanism. plays an important role in combustion processes Extended configuration interaction (CI) calcula and photochemical oxidation. Although global tions are necessary for quantitatively accurate reaction rates have been measured for many of reaction energies. these processes, very little is known about the elementary steps and the free radical intermedi The following MCHF and CI results were ob ates formed in these important reactions. tained: (1) the transition state in the addition 3 reaction of 0( P) to C2H4 to form CH2CH2O has Cs The mechanism originally proposed by symmetry, not C2v symmetry as might be expected; Cvetanovic* involves ;he formation of a shtrt- (2) the hydrogen atom migration D^CHjOt^Ai) s- lived diradical CH^CHjU from the addition of 0(3P) O^CHOt1!^) has a small energy barrier (<10 to the double bond. The diradical undergoes sub kcal/mole) on the singlet surface, but a larger sequent unimolecular reactions such as formation barrier (~50 kcal/mole) on the triplet surface; of "hot" epoxide, hydrogen atom migration to form (3) the has hydrogen atom elimination reaction "hot" acetaldehyde, and other pressure independ CH2CH2O > H+CH2CHO has a small energy barrier ent fragmentations (1): (<5 kcal/mole); and (4) the vinoxy radical

0{3P) + C H ? FRAGMENTATIONS

(I)

Direct observation of CH3, HCO (95%), and CH2CO CHjCHO has a near-infrared electronic transition (4%) by Kanofsky and Gutman? was interpreted as X^A" > 2A1, recently confirmed by experiment. a verification of Cvetanovic's mechanism. How ever, several recent experiments by Lee^ and by These results support the mechanism proposed others4-6 challenge this mechanism and suggest by Lee and co-workers. There are two triplet that the vinoxy radical CH2CHO is a primary surfaces of 0(3P) + C2H4 that lead to two nearly product of the 0 + C2H4 reaction (II): degenerate states of the diradical CH2CH2O. Hy-

(II)

This work was supported by the Erector, Office of Energy Research, Office of Basic Energy Sci ences, Chemical Sciences Division and the Lawrence Berkeley Laboratory Director's Program Development Funds both of which are under the auspices of the U. S. Department of Energy under Contract No. DE-AC03-76SF00098. Equip ment was purchased by the National Science Foundation. 145

drogen elimination to form H + CHgCHO (X 2A") is an energetically accessible pathway in the molec ular beam experiment. There is insufficient en +Brief version of J. Chem. Phys. 76, 481 (1982), ergy, however, for formation of H + CHgCHOfA 2A'). LBL-12756; J. Chem. Phys. .76, 488T1982), The diradical can undergo collision-induced in- LBL-12815; Frontiers of Chemistry, Pergamon tersystem crossing which leads to vibrationally Press, ISC'-, p. 156; LBL-12534. hot acetaldehyde that unimolecularly decomposes 1. R. J. CvetanoviC\ Adv. Photochem. 1, 115 to form CH3 + HCO. The energy correlation diagram (1953). is shown in Fig. 1.1. The electronic states of 2. J. R. Kanofsky and D. Gutman, Chem. Phys. CH2CHO are depicted in Fig. 1.2. Lett. 15, 236 (1982). 3. R.~J. Buss, R. J. Baseman, G. He, and Y. T. Lee, J. Photochem. 17, 389 (1981). 4. G. Inoue and H. Akimoto, J. Chem. Phys. 74, 425 (1980). /'\ 5. H. R. Wendt, H. Kneppe, and H. E. Hunziker, J. Photochem. 17, 377 (1981). 20 " ( \ — 6. K. Kleinermanns and A. C. Luntz, J. Phys. ( \ Chem. 85, 1966 (1981). 0- -. ' \ 3 + C 0t P 2 2. THEORY OF POLYATOMIC PH0T0D1SS0CIATI0NT

. ^'".Y" '» CH2CHO+H _ CH3CO+H CH CH 0 t 1 — CH CO + H _ -20 2 2 2 2 V. Z. Kresin and W. A. Lester, Jr.

(,'3A1 \ $_ CH THCC. 3 The photodissociation of a polyatomic molecule \ CH CH0(JA,) -40 3 can be treated as a quantum transition from the \ ground state (direct photodissociation) or a quasidiscrete intermediate state (indirect pho -60 _ \ todissociation) to a final dissociative state of photofragments. The Born-Oppenheimer approxima _ l — CM CO + H - 2 2 tion (80A) enables the problem to be reduced to one of nuclear dynamics only. Indirect photo- H COCH ; ~ -80 2 2 d^nociation is caused by deviations from the C' A,l \ BOA, i.e., by non-adiabatic interactions. The final dissociative state wavefunction is charac -100 ~ t- terized by both internal and relative transla- ChjCHOi'A,) tional motion, and thus includes discrete as well as continuous factors.

Fig. 1.1. Energy correlation diagram for the 0 + We have developed an adiabatic approach solely C2H4 system. (XBL 816-2323) within the framework of the nuclear problem. It describes the dissociative state dependence on interfragment interaction by vibrational frequen cies that are functions of the interfragment dis tance and by translational functions determined by an effective potential energy that includes the vibrational energy. Our choice of zeroth- order approximation results in a small effect of SO the translational-vibrational interaction, i.e., ~ / 1**"\ final-state interaction, on the final dissocia *0 / \ tive state. 20 / Recent experimental investigations of the pho todissociation of CS2 and NOg have yielded 0 nonstatistical distributions of the fragments. '-->^ 2A' \ Based on our quantum theory of polyatomic photo 20 dissociation, one can prove that an inverse dis tribution of fragments is caused by features of

X A CH.CH-O CH2 = CH-0 CH2-CH=0 the matrix element that describes the transition 40 to the dissociative state.

Fig. 1.2. Electronic state correlation diagram fBrief version of J. Phys. Chem. 86, 2182 (1982) for CH2CHO. (XBL 816-2324) and Chem. Phys. Lett. 87, 392 (198T). 146

3. FIXED-NODE QUANTUM MONTE CARLO FOR MOLECULES^ The radical HgCOO subsequently isoroeri2es or dissociates. Our previous study of 0(3P) + P. 0, Reynolds, D. M. Ceperley,* B. J. Alder,* C2H4 showed that hydrogen atom migration on the and W. A. Lester, Jr. triplet surface has a high barrier. This finding suggests that H migration way not be an accessible This Quantum Monte Carlo (QMC) method joins pathway for 0 + H2CO. Instead, H atom elimina together two seemingly different research areas, tion would occur to form HCO2: namely, quantum chemistry and statistical mechan ics. The hybrid discussed here is a considerable HgCOO—p-H + HCO2 (4) refinement of a technique that has had a long history in theoretical nuclaar and condensed We have undertaken an ab initio study of the matter physics. Unlike many other QMC methods 0(3P) + H2CO aimed at establishing the reaction which simply use Monte Carlo to evaluate expec pathways for this system. tation values using a particular trial wavefunction, the approach we present is a stochastic Adiabatic Approach to Direct Photodissociation solution to the Schrbdinger equation directly. and Chemical Reactions

The basis of the method is to cast the The adiabatic approach applied to indirect Schrodinger equation into the form of a diffusion photodissociation described in article 2 is being

equation4 which is then solved stochastically. applied to the study of direct photodissociation. To reduce the statistical error associated with We shall also investigate the effect of initial such a calculation, we use importance sampling. vibrational excitation on photodissociation dy This procedure is incorporated into the technique namics. The extension of the adiabatic method through an importance function 'r'-r. This func for nuclear dynamics to chemical reactions is tion guides the diffusion process into regions of under way. A chemical reaction can be treated as space where ¥7 is large. Thus, the closer fj ap a quantum transition from a bound-continuous state proximates the actual wavefunction of the system, of reactants to a bound-continuous state of prod the more quickly diffusion increases the proba ucts. Each of these states is analogous to a bility density in the appropriate regions of dissociative state. space. Into this method we have incorporated the "fixed-node" approximation which enables treat Quantum Monte Ca'flo Method ment of Fermi systems such as atoms and molecules. The QMC method described in article 3 has thus He have applied this technique to the computa far been restricted to ground-state properties. tion of the ground-state energies of H£, LiH, In order to determine the feasibility and accu Lip, and H2O. Our results in every case exceed racy of the method for excited-state molecjles, the accuracy of the best configuration interaction we have begun work on the *Ai state of methy calculations. We obtain presently between 80 and lene. By also performing additional calculations 100% of the correlation energy of these molecules on the 3BJ ground state, we hope to obtain an with a statistical error of about the cor- independent theoretical estimate of the contro 2% of 3 relation energy. versial 3i-lAi energy splitting. We are also embarking on a study of the energy barrier to the H + Hj exchange reaction. This work will shed light on nodal structure complexity and its im Brief version of LBL-13356; J. Chem. Phys. TL, plications for the fixed-node approach. 5593 (1982). iLawrence Livermore National Laboratory. 1982 PUBLICATIONS AND REPORTS

4. WORK IN PROGRESS Refer_eg_d_ Journal^

Reaction of 0(3P) with Formaldehyde 1. M. Dupuis, J. J. Wendoloski, T. Takada, and W. A. Lester, Jr., "Theoretical Study of Electro- philic Addition: 0(3P) + C2H4," J. Chem. Phys. The reaction 26, 481 (1982); LBL-12756. 0(3p) + H C0—^-products (1) 2 2. M. Dupuis, J. J. Wendoloski, and W. A. is important in the oxidation of methane, and Lester, Jr., "Flectronic Structure of Vinoxy thus is of interest in combustion and in atmo Radical CH2CHO," J, Chem. Phys. 7±-> 488 (1982); spheric chemistry. It has long been assumed to L8L-12815, proceed via hydrogen abstraction 3. M. Dupuis and J. Pacansky, "Theoretical Study of Cyclopropane and Cyclopropyl Radical: Struc 0(3p) + H C0—^HCO + OH (2) 2 ture and Vibrational Analysis," J. Chem. Phys. _76, 2511 (1982); LBL-12608. Recently, Chang and Barker1 reported the meas urement of a substantial yield (-303!) of a pri 4. V. Z. Kresin and W. A. Lester, Jr., "Theory mary product of mass 44, suggesting that the ad of Polyatomic Photodissociation. Adiabatic dition reaction is an important channel, i.e., Description of the Dissociative State and the Translation-Vibration Interaction," J. Phys. 3 + 0( P) H2CO--^H2CO0 (3) Chem. 86, 2182 (1982); LBL-12861. 147

5. V. Z. Kresin and W. A. Lester, Jr., "Inverse Chemistry, edited by K. J. Laidler, Pergamon, Vibrational Distribution of Photofragments," Oxford, 1982, p. 159-167. Chem. Phys. Lett. 87, 392 (1982); LBL-12607. Invited Talks 6. V. Z. Kresin, "Collective Excitations in n-Electron Systems," J. Phys. Chem. 86, 2187 1. W. A. Lester, Jr., "Introduction to the Cal (1982); LBL-12576. ~~ culation of Potential Energy Surfaces," Workshop on the Dynamics of the Photodissociation of Sim 7. A. S. Dickinson, H. S. Lee, and W. A. Lester, ple Molecules, University of Paris-South, Orsay, Jr., "Close-Coupling Calculations of Li+-H? Dif France, September 1, 1982. fusion Cross Sections," J. Phys. B 15, 1371 (1982); LBL-13983. ~~ 2. W. A. Lester, Jr., "Adiabatic Approach to the Dynamics of Photodissociation," Workshop on the 8. P. J. Reynolds, D. M. Ceperley, B. J. Alder, Dynamics of the Photodissociation of Simple and W. A. Lester, Jr., J. Chem. Phys. 77, 5593 Molecules, University of Paris-South, Orsay, (1983); LBL-13356. France, September 6, 1982.

LBL Reports 3. M. Dupuis, "Electronic Structure Aspects of Photodissociation," Symposium on Electron Corre 1. T. Takada, M. Dupuis, and J. F. King, "Molec lation in Molecules, American Chemical Society ular Symmetry IV: The Coupled Perturbed Hartree- Meeting, Las Vegas, Nevada, March 28-April 2, Fock Method," LBL-14470. 1982.

2. T. Takada and M. Dupuis, "On the Electronic 4. M. Dupuis, "A_b Initio Characterization of the Structure of Cubene CsHg," LBL-14584. H2CO > HgCO Potential Energy Surface," IBM Re search Laboratory, San Jose, California, November 3. T. Takada and M. Dupuis, "Theoretical Study 18, 1982. of the Ally! Radical: Structure and Vibrational

Analysis," L8L-14314. 5. M. Dupuis, "MCHF-CI Study of the H2C0 > H2+C0 Potential Energy Surface," International Discus 4. M. Dupuis and J. J. Wendoloski, "Theoretical sion Meeting on State Specific Photodissociation: Study of the Vinyl Radical: Structure and Vibra Formaldehyde," Berkeley, California, November tional Analysis," LBL-14872. 11-13, 1982.

5. N. Abusalbi, R. A. Fades, T. Nam, 6. M. Dupuis, "Some Aspects of Electronic Struc D. Thirumalai, D. Dixon, D. G. Truhlar, and ture Calculations for Polyatomic Systems," State M. Oupuis, "Electron Scattering by Methane: Ufiiversity of New Vork at Buffalo, New York, Elastic Scattering and Rotational Excitation August 2, 1982. Cross Sections Calculated with Ab Initio Interaction Potentials," LBL-14871. 7. V. Z. Kresin, "Size Quantization of Thin Films, University of Southern California, Los Other Publications Angeles, California, April 1982. 1, W. A. Lester, Jr., M. Dupuis, T. J. O'Donnell, 8. V. Z. Kresin, "Polyatomic Photodissociation," and A. J. Olson, "Some Computational Trends in Howard University, Washington, D.C., July 12, Theoretical Chemistry," in IUPAC Frontiers of 1982. 148

f. Theory of Atomic and Molecular Collision Processes* William H. Miller, Investigator

1. DYNAMICAL MODELS FOR POLYATOMIC REACTION DYNAMICS1"* * * * ^Abstracted from J. Chem. Phys. 76, 2412 (1982) B. A. Waite, S. Schwartz, and w. H. Miller and J. Chem. Phys. 77, 2378 (198"2)\ *A11 calculations involved in this work were car A reliable quantum mechanical description of ried out on a Harris 800 minicomputer supported reactive scattering would clearly be an important by National Science Foundation Grant CHE-79-20181. tool for application in many areas of chemistry. 1. W. H. Miller, N. C. Handy, and J. E. Adams, At present, rigorous treatments are possible for J. Chem. Phys. _72, 99 (1980).

only the simplest reactions, e.g., H + H2 » H;> + H, both because of the limitations of ac 2. DYNAMICAL EFFECTS OF REACTION PATH SYMMETRY; curacy in determining the potential energy sur MODE-SPECIFICITY IN THE UNIMOLECULAR DISSOCIATION face and because of the difficulty of quantum re OF FORMALDEHYDE** active scattering calculations. The difficulties become even more pronounced when one wishes to B. A. Waite, S. K. Gray, and M. H. Miller treat systems involving polyatomic molecular sys tems. The photodissociation of formaldehyde

Approximate treatments are thus of considerable H C0 + hv > H + CO (1) interest, and much progress has been made recently 2 2 utilizing the reaction path Hamiltonian of Miller has attracted considerable experimental and theo et alJ Specifically, a semiclassical multi retical attention as a prototype for reaction channel branching model has been developed for dynamics in a small polyatomic molecule. (See describing a variety of aspects of polyatomic related work in MMRD by Moore* and Schaefer.2) dynamics: state-specific unimolecular decay The particular aspect of interest here is the rates, the tunneling splitting in multidimen question of mode-specificity in the unimolecular sional double-well potentials, and resonances dissociation, i.e., the question of whether or in reactive scattering. Numerical calculations not the rate of dissociation depends only on the based on this model show it to give a quantita total excitation energy of the molecule or also tively useful description of these phenomena. on the particular modes of the molecule that are excited. Another approximate model based on the reac tion path Hamiltonian exploits the fact that The path for reaction (1) has been shown from chemical reactions are usually local phenomena; quantum chemistry calculations^ to be planar, i.e., even in a large molecular system, the reac i.e., C symmetry. From this fact it has been tion typically involves only a few degrees of pointed sout uhat the reaction will at least show freedom in an intimate way. It is therefore nat mode-specificity between the states of different ural to separate the complete polyatomic system irreducible representations of C symmetry, into a "system," the reaction coordinate and the i.e., A' and A" states. Calculations s based on a few degrees of freedom that are strongly coupled "symmetry adapted transition state theory"—i.e., to it, and a "bath," the remaining {perhaps many) the assumption that the dynamics is as statisti degrees of freedom that are only weakly coupled cal as it can be within symmetry restrictions—are to the reaction. This "system-bath" decomposi shown in Fig. 2.1. The energy region relevant to tion of the reaction path Hamiltonian has been the experiments2 is ~5 kcal/mole below the carried out, and it provides a framework for classical threshold, and one sees that rates for utilizing an accurate dynamical treatment of a the two symmetries differ by a factor of ~20 at few degrees of freedom (the "system") together the same energy. Symmetry-adapted transition with an approximate treatment of the much larger state theory is shown to be a general concept, number of degrees of freedom (the "bath") that applying to any reaction for which the transition exist but which are not strongly involved in the state has (or almost has) some geometrical sym progress. metry.

Considerable progress has thus been made in Actual dynamical calculations of the state- the ability to describe the dynamics of poly specific unimolecular rate constants are shown in atomic systems. These techniques should find Fig. 2.2 and one sees here that there is a sig many applications in the theoretical modeling nificant degree of "dynamical" mode-specificity of chemical processes at the molecular level. in addition to that demanded by symmetry.

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sci ences, Chemical Sciences Division of the U. S.| Department of Energy under Contract No. \ DE-AC03-76SFO0098. \ 149

^Abstracted from J. Am. Chem. Soc. 105, 216 (1983); 0. Chem. Phys. 78, 259 {.USTT; and LBL-15443, 0. Phys. Chem., in press. (All calculations involved in this work were car ried out on a Harris 800 minicomputer supported by National Science Foundation Grant CHE-79-20181. 1. C. B. Moore and Associates, this Annual Re port. 2. H. F. Schaefer and Associates, this Annual Report.

1982 PUBLICATIONS AND REPORTS

Refereed Journals

1. C. 0. Cerjan, S.-h. Shi, and W. H. Miller, O 5 "Applications of a Simple Dynamical Model to the Reaction Path Hamiltonian: Tunneling Corrections E - V*P (kcol/mole) to Rate Constants, Product State Distributions, Line Widths of Local Mode Overtones, and Mode- Fig. 2.1. Microcanonical rate constant for the Specificity in Unimolecular Decomposition," J. reaction HjCO » Hj + CO (for total angular Phys. Chem. 86, 2244 (1982); LBL-12842. momentum J = 0) for the symmetries A' and A", as ZP a function of total energy E relative to V« 2. B. A. waite and W. H. Miller, "A Semiclassi- cal Multichannel Branching Model for Describing (the barrier height plus zero point energy of the State-Specific Unimolecular Decomposition and transition state). (XBL 825-10146) Other Dynamical Processes in Polyatomic Molecular Systems," J. Chem. Phys. K, 2412 (1982); LBL-13433.

3. W. H. Miller, "Effect of Reaction Path Curva 1 1 ' 1 • 1 ture and Dimensionality on the Accuracy of Class ical Transition State Theory," J. Chem. Phys. 76, I014 « • - 4904 (1982); LBL-13627.

u - - 4. P. S. Dardi and S. K. Gray, "Classical and „ •L- ° * ° \o - - Quantum Mechanical Studies of HF in an Intense Laser Field," J. Chem. Phys. 77, 1345 (1982); 10 .•.»° _ se c I0 LBL-14060.

I08 - - 5. W. H. Miller and S. Schwartz, "System-Bath iii O ° Decomposition of the Reaction Path Hamiltonian 77 m and Bg 2. S. K. Gray, "Classical Aspects of the Laser states. (XBL 823-11179) Excitation of a Morse Oscillator," L8L-14717. 150

3. S. K. Gray and U. H. Miller, "Classical Model tion in Liquids," LBL-15329. for Electronic Degrees of Freedom: Charge Trans fer in Na + I Collisions," LBL-14808. 10. W. H. Miller, "Symmetry-Adapted Transition State Theory: Non-Zero Total Angular Momentum," 4. B. A. Waite, S. K. Gray, and W. H. Miller, LBL-15443. "Mode-Specificity in the Unimolecular Dissocia tion of Formaldehyde (HpCO » H2 + CO), a 11. W. H. Miller, "On the question of Mode-Spe Two-Mode Model," LBL-14855. cificity in Unimolecular Reaction Dynamics," LBL-15463. 5. L. M. Hubbard and W. H. Miller, "Application of the Semiclassical Perturbation (SCP) Approxi 12. S. Schwartz and W. H. Miller, "System-Bath mation to Diffraction and Rotationally Inelastic Decomposition of the Reaction Path Hamiltonian Scattering of Atoms and Molecules from Surfaces," II. Rotationally Inelastic Transition in the

LBL-15068. 3-d H + H2 Reaction," LBL-15464.

6. J. Bicerano, H. F. Schaefer, and W. H. Miller, "Structure and Tunneling Dynamics of Malonalde- hyde, a Theoretical Study," LBL-15155. Invited Talks

7. w. H. Miller, "Symmetry-Adapted Transition 1. W. H. Miller, "On the Relation of Quasiperi- State Theory and a Unified Treatment of Multiple odic on Chaotic Classical Mechanics to Semiclass Transition States," LBL-15069. ical Eigenvalues of Polyatomic Molecules and to Mode-Specificity in Unimolecular Reaction Dynam 8. L. M. Hubbard, S.-h. Shi, and W. H. Miller, ics," Austrian Workshop for Theoretical Chemis "Multi-Channel Distorted Wave Born Approximation try, Mariapfarr, Austria, February 16-19, 1982. for Reactive Scattering," LBL-15226. 2. W. H. Miller, "Dynamical Effect of Reaction 9. D. P. Ali and W. H. Miller, "Effect of Elec Path Symmetry," ACS National Meeting, Kansas tronic Transition Dynamics on Iodine Recombina City, Missouri, September 12-17, 1982. 151

g. Photoetectron Spectroscopy"

David A. Shirley, investigator

Introduction. This project is dedicated to This leads to the new data analysis. By studying new phenomena by the use of photoelectron removing the atomic cross section and expressing spectroscopy and related phenomena. the modulations as a function of electron momen tum, the experimental data can be analyzed if we A major breakthrough was achieved in 1982: adopt high resolution Fourier methods (following the discovery of angle-resolved photoemission article 2). Application of this new approach to extended fine structure (ARPEFS) for surface our measurements of S(ls) photoemission from structure determinations (articles 1 and 2). c(2x2)S/Ni(0Ol) and p(2x2)S/Cu(001) is shown in Normal photoelectron diffraction was applied to Fig. 1.1. The four nearest substrate atoms appear oxygen on copper to solve that controversial as the first three peaks: the peak near 2 A cor structure (article 3). Angle-resolved photo- responds to the atom closest to the detector, the emission was used to study the two-dimensional next peak (-3.5 A) represents two atoms, and the band structure of silver on a copper substrate peak at 4.4 A corresponds to the fourth neighbor {article 4) and to follow the evolution of which sits behind the S from the detector. The three-dimensional structure (article 5). High- intensity of the third peak is the largest because resolution spectra of Ag(lll) were also obtained backscattering is favorable; the first peak is (article 6). A high-resolution, energy-loss much larger for S/Cu than for S/Ni because the spectrometer was finished and tested (article 7). polarization vector was pointed more toward this atom for the Cu measurements. By combining the Gas-phase studies included extension of photo- ARPEFS peak position and intensity information, emission spectroscopy using synchrotron radiation into a totally new energy regime—up to 3300 eV {article 8). Photoelectron angular distributions from a 4f shell were measured for the first time (article 9), and a definitive study was carried out on the helium n = 2 satellite problem (article 10). Photoelectron angular distributions were measured from NgO (article 11) and Hg (article 12). Finally, rotational relaxation in H? was studied (article 13), establishing the nonexist ence of a rotational temperature.

1. DIRECT SURFACE STRUCTURE DETERMINATION WITH PHOTOELECTRON DIFFRACTION*^

J. J. Barton, C. C. Bahr, Z. Hussain,* S. W. Robey, J. G. Tobin, L. E. Klebanoff, and D. A. Shirley

Our development of energy-dependent photo electron diffraction as a surface structure tool advanced dramatically in 1982. We now have a new theoretical basis and a new data analysis that provide the surface structure information direct ly. We call this new approach angle-resolved photoemission extended fine structure (ARPEFS).

The new theoretical advance gives an analytic single-scattering formula incorporating approxi mations valid for our measurements. The formula contains one cosine term for each nearby substrate atom. The frequency of the cosine depends on the substrate-atom and detector positions; the cosine amplitude depends on the substrate-atom and polar ization directions. 0 5 10 Apath length (A) *This work was supported by the Director, Office of Energy Research, Office of Basic Energy Fig. 1.1. Comparison of Fourier transform ampli Sciences, Chemical Sciences Division of the U.S. tudes for (a) ARPEFS from p(2x2)S/Cu{001), (b) Department of Energy under Contract No. ARPEFS from c(2x2)S/N1(00l), and (c) SEXAFS from DE-AC03-76SF00098. It was performed at the C(2x2)S/Ni(001)(Ref. 1). The ARPEFS range in Stanford Synchrotron Radiation Laboratory, which k-spe*e was extended using the auto-regressive is supported by the NSF through the Division of estimation method prior to Fourier transformation. Materials Research. (XBL 8212-11283) 152

we car. directly verify the surface structure for c(2x2) (v^x2v^)R45° S/Ni and report that S occupies the four-fold hollow site on Cu(OOl) at a bond length of 2.28 A.

+Brief version of LBL-14645. ^University of Petroleum and Minerals, Dhahran, Saudi Arabia. 1. S. Brennan, 0. Stoehr, R. Jaeger, Phys. Rev. B 24, 4871 (1981).

2. HIGH RESOLUTION FOURIER ANALYSIS WITH AUTO- ffi 0(o,b) REGRESSIVE LINEAR PREDICTION"1'

J. J. Barton and D. A. Shirley

Fourier analysis of a sequence containing sinusoidal signals usually proceeds by multiply ing the sequence by a window function and apply 0(d) ^Q- 'jQQ-- 5Q— ,QQ- _ ing a fast Fourier transform. The ability to 150 v resolve two similar frequencies is then deter mined by the length of the sequence and is in Kinetic energv (eV) dependent of the data's signal-to-noise power ratio. This creates a serious problem for physi Fig. 3.1. NPD experiment and theory for cal measurements that are restricted in their c(2x2)0/Cu(001): (a) experiment; (b) theory, range: no matter how carefully the measurement djL = 0.8 A, hollow; (c) theory, d± = 0.1 A, hol is made, no improvement in resolution can be low; and (d) theory, d1 = 1.4 A, bridge, V0 = obtained. Fortunately, engineers interested in 10 eV. NPB experiment and theory for (>/2~ x 2*£") acoustic and seismic Fourier analysis have devel R45° 0/Cu(001): (e) experiment;'(f) theory, dL = oped an auto-regressive linear prediction for 0.8 K hollow for c(2x2); (g) theory, 1:1/2 extrapolating a sequence assuming only that it weighted sum of 0.8 A hollow and 0.1 A hollow, always has the same average frequency content. c(2x2) calculations; and (h) theory, 1:1/2 weight Figure 1.1b {see preceding article 1) shows the ed sum of 0.8 A hollow and 1.4 A bridge, c(2x2) auto-regressive Fourier amplitude for ARPEFS of calculations, V = 10 eV. (XBL 827-10738A) S/Ni(001). For comparison Fig. 1.1c shows the 0 normal Fourier analysis of the SEXAFS curve.' By comparing the largest peaks in these curves, v/e see that the auto-regressive method doubles Fourier resolution. The /? x 2/7 structure has a similar NPD curve, indicating the same local site geometry for the c(2x2) sublattice. The site of the additional fBrief version of LBL-14758. oxygen is unknown, as suggested by Fig. 3.1. 1. S. Brennan, 0. Stoehr, and R. Jaeger, Phys. Rev. B 24, 4871 (1981). * * *

''Brief version of LBL-14188- ; Phys. Rev. B 26, 3. NORMAL PH0TOELECTR0N DIFFRACTION OF 0/Cu(001): 7076 (1982). A SURFACE STRUCTURAL DETERMINATION* ^Watkins-Johnsfn Company, Palo Alto, CA 94304. ^Research Laboratories, Polaroid Corporation, J. G. Tobin, L. E. Klebanoff, D. H. Rosenblatt,* waltham, MA 0'.'154. R. F. Davis,5 E. Umbach,11 A. G. Baca, D. A. Vhysik-Depa.-tment, Technische Universitat, Shirley, Y. Huang," w". M. Kang," and S. Y. Tong" Munchen, W. Germany. "Department of Physics, University of Wisconsin- In the normal photoelectron diffraction (NPD) Milwaukee, Milwaukee, WI 53201. technique, the photoemission intensity of an adsorbate core level is measured normal to the surface as a function of photon (and thus kinetic) 4. THE TWO-DIMENSIONAL VALENCE ELECTRONIC energy. An intensity-kinetic energy curve similar STRUCTURE OF A MONOLAYER OF Ag ON Cu(001)+ to a low energy electron diffraction (LEED) I-V curve is generated which, when compared to theo J. G. Tobin, S. W. Robey, and D. A. Shirley retical curves, may yield a surface structure. The electronic structure of the valence bands Oxygen adsorbs on Cu(001) with difficulty, of bulk three-dimensional metals has been a producing a c(2x2) structure at low exposures and subject of great experimental and theoretical a (/? x Z^Z) R45° structure at higher exposures. interest. Included in this have been a number of The two systems were studied at the Stanford Syn investigations into the nature of states local chrotron Radiation Laboratory on Beam Line 1-1. ized in the topmost layer of single crystal sur In the c(2x2) structure, oxygen occupies the four faces and theoretical calculations of electronic behavior in monolayer metal slabs. fold hollow site, with di = 0.80(5) A (Fig. 3.1). 153

Here, we present the first complete angle behavior such as surface states. Experimentation resolved photoemission (ARP) investigation into has also extended into the realm of observing the the valence band structure of a single layer of a development from atomic to three-dimensional metal deposited upon a different metal single electronic structure in metal clusters* and the crystal. Using ARP excited by polarized vacuum layer-by-layer band structure of physisorbed Xe.2 ultraviolet radiation of 21.2 eV (Hel) and 16.3 In this article we report the first complete eV (Nel), the valence bands of the Ag monolayer experimental observation of the transition from were mapped vs the parallel component of the two-dimensional to three-dimensional valence crystal momentum of theoutgoing electron. electronic structure in metal overlayers. By using two different photon energies, the Angle resolved photoelectron spectroscopy is dependencies of the band binding energies upon the method of choice, since it allows a direct •the perpendicular component of the crystal momen measurement of the dispersion relations of the tum could be tested. It was found that, while metal valence bands and differentiates between the bands disperse as functions of the parallel 2-D and 3-D dependences. momentum, they are independent of the perpendicu lar component (Fig. 4.1). This is conclusive By measuring the dependences of the binding evidence of two-dimensional metallic behavior in energies of the states observed in a Ag overlayer a monolayer of c(10x2)Ag/Cu(001). Also, using upon the momentum parallel to the direction of group theoretical selection rules, all of the Ag growth of the overlayer, the evolution to 3-0 features have been assigned upon the basis of the behavior was observed at exposures of less than polarization dependencies of the features. or equal to 5 monolayers of Ag. Accompanying these band mapping results, cross section (Fig. 5.1) and final state effects were also seen that suggest convergence to a structure very similar "Brief version of LBL-15133. to bulk single crystal Ag(lll).

BF(eV) +Brief version of LBL-15134. 1. S.-T, Lee, G. Apai, M. G. Mason, R. Benbow, and Z. Hurych, Phys. Rev. B 23, 505 (1981). 2. T. Mandel, G. Kaindl, W. D. Schneider, and W. Fischer, submitted to Phys. Rev. Lett.

• Ag(lll) • 5MLc(IOx2)Ag/Cu[OOI) - ratio to Ag(IH) = a57±Q09- *4MLc(IOx2)Ag/Cu(0a) - ratio to Agl»D=0.52±009 ratioto5ML=092±Q07 -

(&"')

Fig. 4.1. Plot of Ag valence band binding energy vs ki| in two directions across the Surface Brillouin Zone of c(10x2)Ag/Cu(001). (XBL 832-1272)

5. THE EVOLUTION TO THREE-DIMENSIONAL VALENCE 22 24 26 28 BAND STRUCTURE IN Ag OVERLAYERS ON Cu(001)f Photon energy (eV)

J. G. Tobin, S. W. Robey, L. E. Klebanoff, and Fig. 5.1. The ratio of the intensity of the high D. A. Shirley binding energy half of the silver valence bands to the intensity of the low binding energy half There has been an immense amount of work done of the silver valence bands is plotted as a func investigating the three-dimensional electronic tion of photon energy for thd samples Ag(lll) and structure of bulk metals. More recently, interest 4 and 5 monolayers of c(10x,')Ag/Cu(001). has centered upon elucioation of two-dimensional (XBL 832-1278A) 154

6. HIGH RESOLUTION ANGLE-RESOLVED PHOTOEMISSION 7. CONSTRUCTION OF A HIGH RESOLUTION ELECTRON STUDY OF THE VALENCE BAND STRUCTURE OF Ag(lll)+ ENERGY LOSS SPECTROMETER

J . G. Tobin, S. W. Robey, 0. A. Shirley, W, 0. H. Rosenblatt,"*" A. G. Baca, and D. A. Shirley Gignaignac,c * J. G. Nelson,* and R. S. Williams* We have completed construction of a high The electronic structure of three-dimensional resolution electron energy loss spectrometer bulk crystals continues to be of great interest (EELS) for the study of vibrations at surfaces. in condensed phase material science. Advances in A monoenergetic beam of electrons is produced by photon sources, such as improvements in synchro a double-pass electron monochromator based on tron radiation storage rings, and accompanying hemispherical sectors. The single pass analyzer advances in spectrometer design have allowed can be rotated in two independent directions. increasingly improved resolution to be achieved The spectrometer is in a UHV chamber with LE£D» in angle-resolved photoemission. Auger, and ion sputtering capabilities. A reso lution of 32-40 car* is obtained. Angle-resolved photoemission is a technique that can be used as a direct probe of the disper We have carried out a coverage dependent study sion relations of the valence bands, i.e., the of the system O2+ Cu(OOl). Previously, Sexton dependence of the t-inding energies upon crystal has studied this system at crverages of 50L and momentum. 5000L,* while Lehwald and Ibdch have studied the similar system O2+ Ni(001).2 As can be seen in Here, results are presented that are an exten Fig. 7.1, there is a low coverage 0-Cu stretch at sion and improvement upon an earlier experiment.! 350 cm-1, which shifts to 290 cm-1 at high cover- Included are higher resolution data collected at normal emission along the F to L line {Fig. 6.1] in the three-dimensional Brillouin Zone (h\> = Cu(OO0* 0 6-3? eV) and off-normal data collected by hv = 14 2 and 21 eV. Presently, data analysis is being pur E , = 2 eV sued, including art attempt to extract lifetimes from peak widths.

•Brief version of LBL-15135. — •qOOO 1.8 = 0.84 'Department of Chemistry, University of California, {/2 x 2 -/z) R45° Los Angeles, CA 90024. 1. P.3. Wehner, R, S. Williams, S. 0. Kevan, D. Denley, and 0. A. Shirley, Phys. Rev. B 19, 6164 [1979). 400L, 0 = 0.56 ' cl2*2)*(-/?»2-/?)R45'\

~ 2G0L,fl:O.5O • cfH*2l ,

-• 50 L .6 = 0.46 ;

- ,djL,8*0.3& •

- (OL.5 = 0.55

' SL,e=0.3l

0.2 L.fl= 0,08

Energy loss (cni1) Fig. 7.1. EELS spectra of O-Cu(OOl) as a function of O2 exposure, taken in the specular direction with both an angle of incidence (Qi) and an angle

of reflection {&r of 65°], and an impact energy of 2 eV. The spectra were taken at 300 K after a brief annealing to 175 K. The magnitude of the exposure, observed LEED pattern [if different fro Fig. 6.1. Plot of binding energy vs crystal (Ul)], and a rough estimate of fractional oxyg<- momentum along the r-line in the 3-0 Brillouin coverage are given for each spectrum. Zone. (XBL B32-1279A) (XBL 8210-4773 155 ages. At intermediate coverages the spectra are 9. PHOTOELECTRON MEASUREMENTS OF THE MERCURY 4f, a superposition of the low and high coverage spec 5p, and 5d SUBSHELLS1" tra, similar to what occurs on Ni(OOl), although the 60 cm-1 shift is smaller than the 120 cnr1 P. H. Kobrin, P. A. Heimann, H. G. Kerkhoff, shift observed in Ni(001). D. W. Lindle, C. M. Truesdale, T. A. Ferrett, * * * U. Becker,* and D. A. Shirley Mercury is the heaviest stable element with THatkins-Johnson Company, Palo Alto, CA 94304. both closed electronic shells and an appreciable 1. B. A. Sexton, Surf. Sci. 88, 299 (1979). vapor pressure at low temperatures. Relativistic 2. S. Lehwald and H. Ibach, in Vibrations at effects in photoionization are thus readily stud Surfaces, edited by R. Caudano, 0. H. Gilles, and ied in mercury. A. A. Lucas, Plenum, New York, 1982, p. 137. We have measured photoelectron spectra using the double-angle, time-of-flight (0AT0F) method,1 8. THRESHOLD MEASUREMENTS UF THE K-SHELL in which the pulsed time structure of synchrotron PH0T0ELECTR0N SATELLITES IN Ne AND Art radiation from the SPEAR storage ring is used to measure the time-of-flight electrons ejected at P. H. Kobrin, S. Southworth,* C. M. Truesdale, two angles. This method enables us to measure D. W. Lindle, U. Becker,5 and D. A. Shirley simultaneously the relative cross sections, subshell branching ratios, and angular distribution Photoelectron spectra of closed-shell atoms asymmetry parameters of each subshell. Using typically sho1.'/ an intense peak at the binding photons in the energy range 50 to 270 eV, ioniza energy of each electronic subshell and weaker tion of the 4f, 5p, and 5d subshells was observed satellite peaks at high binding energies. The (see Fig. 9.1). satellites arise via photoionization to higher energy states of the ion that are approximately In this energy range, the 5p and 5d ionizations described by configurations formed by the removal both go through Cooper minima, and the 4f ioniza of a core electron and the promotion of a valence tion exhibits a delayed onset because of a large electron to a higher subshell. The study of these centrifugal barrier in the 4f » £g channel. These satellites is important for an understanding of effects manifest themselves in each of the observ the many-particle nature of photoionization, which able parameters. Several theoretical techniques can in turn yield insight into the details of have been applied to mercury photoionization, electron correlation in the atom.

The feasibility of studying core-level photoemission satellites in gases at high photon ener gies (up to 3430 eV) has been proved with the use kinetic energy (eV) of synchrotron radiation and time-of-flight detec tion. K-shell satellites in neon were studied i.i! 1 near threshold, in the adiabatic limit, for which cuuu ' 1 the relative intensities were 20-40$ lower than Hg l'5d in the high-energy limit. The "conjugate shake- up" state was not observed, in contrast to pre C h>- = 120 eV ger - 1 c Au dictions of many-body perturbation theory. In ra argon, a K-shell satellite was observed, confirm 5D ing a calculation2 using shake-up theory. Tenta i^ 1OO0 tive evidence was obtained that the satellite 4f 1/2 3/2 - intensity increases with energy. en -t-» ! 4f * * * c 5/ 2 7/' 2 1\ l| , 13 'i ' o r\ ; \ +Brief vers .on of LBL-15042. o -^•v^/v^- / v * v i *National Bureau of Standards, Washington, D.C. 0 """l ' 1*1 I I 1 1 i . . . 1 I v r'v'l 20234. 150 100 50 ^Institut fur Strahlungs- urd Kernphysik, Tech- nische Universitat Berlin* lu'O Berlin 37, W. TOF nsec) Germany. 1. T. Ishihara, J. Mizuno, and I". Watanabe, Fig. 9.1. A TOF spectrum of Hg vapor. The 4f Phys. Rev. A 22, 1552 (1980). peak at 131 eV is due to second-order light. 2. K. G. DyaTT, private communication. (XBL 8210-2998) 156

among them the relativistic random-phase approxi a new calculation by Berrington et al.,4 which mation with exchange2 and the Dirac-Slater fits the present data extremely well. method.^ Comparisons are made with these and other theories. * * * * * * +Brief version of LBL-15094. *Institut fur Strahlungs-und Kernphysik, Tech- +Brief version of LBL-14759. nische Universit'a't Berlin, 1000 Berlin 37, W. *Institut fur Strahlungs-und Kernphysik, Tech- Germany. nische Universitat Berlin, 1000 Berlin 37, H. 1. J. M. Bizau, F. Wuilleumier, P. Dhez, 0. L. Germany. Ederer, T. N. Chang, S. Krummacher, and 1. S. Southworth, C. M. Truesdale, P. H. Kobrin, V. Schmidt, "hys. Rev. Lett., 48, 588 (1982). D. VI. Lindle, W. D. Brewer, and 0. A. Shirley, J. 2. V. L. Jacobs and P. G. BurTce, J. Phys. B £, Chem. Phys. 76, 143 (1982). L67 (1972). 2. V. Radojevic and W. R. Johnson, Phys. Lett. 3. T. N. Chang, J. Phy*. B _13, L551 (1980). 92A, 75 (1982). 4. K. A. Berrington, P. G. Burke, W. C. Fon, and 3. B. R. Tambe and S. T. Hanson, private commun K. T. Taylor, J. Phys. B JL5, L603 (1982). ication.

10. PHOTQWH17.AT10N OF HELIUM TO He*(n=2): AUTOIONIZATION AND FINAL-STATE SYMMETRY1 11. PH0T0ELECTR0N ANGULAR DISTRIBUTIONS OF THE

N20 OUTER VALENCE 0RBITALS IN THE 19-31 eV PHOTON 0. W. Lindle, T. A. Ferrett, U. Becker,* P. H. ENERGY RANGE"*" Kobrin, C. M. Truesdale, H. G. Kerkhoff, and D. A. Shirley C. M. Truesdale, S. Southworth,* P. H. Kobrin, D. W. Lindle, and D. A. Shirley The energy dependences of the partial cross section snd asymmetry parameter for simultaneous The N2O molecule has the ground *;e valence 2 photoionization and photoexcitation to the electronic configuration (6O) (1TI)-\ ,J2(2„)4< He+(n=2) ionic state have been measured for pho As part of a continuing program to study photo- ton energies between 67.4 and 90 eV. Below the emission from triatomic molecules, we have meas He+(n=3) threshold at 73 eV, a series of Rydberg ured the vibrationally averaged partial cross states leading to this threshold can be excited, sections and asymmetry parameters for the first with subsequent autoionization to either the four ionic states (X,A,B, and C) of NjO* formed by ground ionic state, He+(n=l), or the first excited ionization of these orbitals at photon energies ionic state, He+(n=2). Our measurements of the of 19-31 eV, using VUV radiation at the Stanford partial cross sections and the asymmetry param Synchrotron Radiation Laboratory. Vibrationally eters for production of these two ionic states in resolved results for the A and C states were also the neighborhood of the autoionizing resonances obtained. Two time-of-flight detectors, at 0* allow the determination of the parameters describ and 54.7° relative to the photon polarization ing these Fano-type resonances. In addition, the axis, were used to detect electrons ejected from simplicity of the He system allows the calculation the ionizedj^amp1a.* As an example, the results of individual dipole and Coulomb matrix elements for the X2ii2it state are shown in Fig. 11.1. Of between the ground, excited, and continuum levels special interest is the similarity of the 0 param involved in the autoionization process. eter of tho N20+ X state and that of the X state in C02+, also shown in the figure.

The nonresonant data, taken at both higher and lower photon energies than the resonance region, yield information about the symmetry of the He+(n=2) final state. This symmetry is defined in "'"Brief version of LBL-15287. terms of the ratio, R, of the relative populations ^National Bureau of Standards, Washington, D.C. of the He+(2p) and He+(2s} states, which are 20234. effectively degenerate in a photoemission experi 1. S. Southworth, C. M. Truesdale, P. H. Kobrin. ment. The ratio R can be obtained from the meas D. W. Lindle, W. 0. Brewer, and D. A. Shirley, ji + ured asymmetry parameter for the He (n=2) final Chem. Phys. Uy 143 (1982). state.1 Previous calculations of R have dis 2. C. E. Brion and K. H. Tan, J. Electron Spec- agreed significantly,2>3 especially just above trosc. Relat. Phenom. jj>, 241 (1979). the He+(n=2) threshold. Our measurements sup 3. T. A. Carlson, P. R. Keller, J. W. Taylor, port the results of Jacobs and Burke, as well as T. A. Whitley, and F. A. Grimm, to be published. 157

The rotational selection rules for the process

Z H2 (xV,v",J") + h« » H* (X E* v',J') + e-(Ek,Z)

have been shown to be J' = J" (Q branch) and J' = J" * 2 (S and 0 branches).1-3 Theoretical calcu lations of the photoelectron asymmetry parameter indicated that BQ (J1 = J") had a value close to 2.0 and was insensitive to the theoretical method employed and that 65 (J' = J" * 2) had a value much less than 2.0 and depended strongly on the method of coupling between the p and f partial waves.3-8 Our values for BS at 584 A and 736 A + 1 for H2 (v = 0), 0.87 ± 0.19 and 0.08 ± 0.15, respectively, illustrate the increased coupling between the p and f photoelectron waves with increased photon energy.

jBrief version of LBL-13998. *The Aerospace Corporation, Los Angeles, CA 90009. §EXX0N Research and Engineering Co., Linden, NJ 07036. 1. J. M. Sichel, Mol. Phys. lji, 95 (1970). 2. R. N. Dixon, G. Duxbury, M. Horani, and J. Rostas, Mol. Phys. 22, 977 (1971). 3. D. Dill, Phys. Rev. A 6_„ 160 (1972). 4. B. Ritchie and B. R. Tambe, J. Chem. Phys. 58, 755 (1978). 5. N. Chandra, in Abstracts of Papers, 10th 18 20 22 24 26 28 30 32 Intern. Conf. Phys. Electron Atom. Coll., Photon energy (eV) Commisariat a l'Energie Atomique, Paris, 1977, p. 1210. Fig. 11.1, Upper panel: Cross section for the + 6. Y. Itikawa, Chem. Phys. 28, 461 '1978). N20 X state. The present resul ts are shown by 7. Y. Itikawa, Chem. Phys. 30, 109 (1978). filled circles, an (e,2e) study by Brion and Tan^ 8. Y. Itikawa, Chem. Phys. 37. 401 (1979). by open circles, and the Multip e Scattering Model calculations (MSMXa) of Whitley and Grinm3 by solid curves. Lower panel: Fil led cVcles are + 13. ROTATIONAL RELAXATION IN SUPERSONIC BEAMS our B(E) results for the N20 X state, and tri- OF HYDROGEN BY HIGH RESOLUTION PHOTOELECTRON angles show our results for e{e)o f the x2nglTig state of C02+, which is plotted to show the sim- SPECTROSCOPY* ilarity between n molecular ioni zation for the two 5 molecules. (XBL 8212-12254) J. E, Pollard,* D. J. Trevor, J. E. Reutt, Y. T. Lee, and D. A. Shirley

The rotational relaxation of n-H^, p-H^, D^, and HD was studied by means of rotationally re solved photoelectron spectroscopy using a colli- mated supersonic molecular beam.l The free jet expansion provides a system in which the internal degrees of freedom of the molecules are initially 12. ROTATIONALLY RESOLVED PHOTOELECTRON ANGULAR in contact with a rapidly cooling translation DISTRIBUTIONS FOR H$ (v'=0) AT x = 584 A AND bath. During the early (collisional) part of the 736 A+ expansion, the internal modes can relax by trans ferring energy into translation. In the later J. E. Pollard/ D. J. Trevor,5 J. E. Reutt, Y. T. stages, the rotational and translational modes Lee, and D, A. Shirley lose contact with one another. Since there is no mechanism for internal equilibrium among rotation The measurement of photoelectron angular al modes, the "rotational temperature" is then distributions for selected rotational transitions meaningless. One motivation for this work was to of molecules is in principle a valuable probe of ascertain the (non-thermal) distribution of rota the dynamics of the photoionization process as tional excitation. The details of the relaxation well as a very sensitive test of the theoretical process can be elucidated by measuring the rota description of the behavior of photoelectrons in tional and vibrational state distributions of the the continuum. We have measured the photoelectron molecules as functions of the stagnation asymmetry parameter for Hg4" (v'=0) for the S conditions. rotational branch at i = 584 A and 736 A, using a supersonic beam of n-H2 and a high resolution photoelectron spectrometer. Rotational state distributions of hydrogen were determined from the relative intensities of 158

the Q branch rotational components for a wide 8. 0. E. Pollard, D. J. Trevor, J. E. Reutt, range of stagnation pressures with nozzle temper Y. T. Lee, and 0. A. Shirley, "Rotationally atures from 300-700 K. Significant deviations Resolved Photoelectron Spectroscopy of n-H?, from a Boltzmann distribution were observed for P-H2, HD, and D2," J. Chem. Phys. 77, 34 (1982); those cases in which the degree of rotational L8L-13696. relaxation was substantial. HO was found to relax after undergoing only one tenth of the 9. Z. Hussain, E. Umbach, D. A. Shirley, number of collisions required to relax Hj or D?, J. StKhr, and J. Feldhaus, "Performance and Appli presumably because the unsymmetrical HD molecule cation of a Oouble Crystal Monochromator in the alone can relax via AJ = ±1 transitions. The Energy Region 800 <_ hj < 4500 eV," Nucl. Instrum. state-to-state rate constants method of Rabitz Meth. ^95, 115 (1982); LBL-12729. and Larci^ was used to model the relaxation of P-H2 and was confirmed to be quite effective in 10. P. H. Kobrin, U. Becker, S. Southworth, accounting for their experimentally observed pop ulation distributions. C. H. Truesdale, 0. W. Lindle, and D. A. Shirley, "Autoionizing Resonance Profiles in the Photo electron Spectra of Atomic Cadmium," Pbys. Rev. A 26, 842 (1982); L8L-13304.

fBrief version of LBL-14279. 11. D. H. Rosenblatt, S. D. Kevan, J. G. Tobin, 'The Aerospace Corporation, Los Angeles, CA 90009. R. F. Davis, M. G. Mason, D. R. Denley, 0. A. ^EXXON Research and Engineering Co., Linden, NJ Shirley, Y. Huang, and S. Y. Tong, "Normal Photo 07036. electron Diffraction Studies of Selenium and Sul 1. J. E. Pollard, D. J. Trevor, Y. T. Lee, and fur Overlayers on Ni(Oll) and Ni(lll)," Phys. Rev. 0. A. Shirley, J. Chem. Phys. 77,, 4818 (1982). B 26, 1812 (1982); L8L-13410. 2. H. Rabitz and S.-H. Lam, J. Chem. Phys. 76, 273 (1982). ~ 12. D. H. Rosenblatt, S. D. Kevan, 1. G. Tobin, R. F. Davis, M. G. Mason, D. A. Shirley, J. C. Tang, and S. Y. Tong, "Off-normal Photoelectron 1982 PUBLICATIONS AND REPORTS Diffraction Study of the c(2x2) Selenium Over- layer on Ni(OOl)," Phys. Rev. B 26, 3181 (1982); Refereed Journals LBL-13268.

1. S. H. Southworth, C. M. Truesdale, P. H. 13. J. E. Pollard, D. J. Trevor, Y. T. Lee, and Kobrin, 0. W. Lindle, W. 0. Brewer, and D. A. D. A. Shirley, "Rotational Relaxation in Super Shirley, "Photoionization Cross Sections and sonic Beams of Hydrogen by High Resolution Photo Photoelectron Asymmetries of the Valence Orbitals electron Spectroscopy," J. Chem. Phys. 77, 4818 of No," J. Chem. Phys. 76, 143 (1982); LBL-12907. (1982); LBL-14279.

2. C. M. Truesdale, S. Southworth, P. H. Kobrin, 14. J. G. Tobin, L. E. Klebanoff, D. H. D. W. Lindle, G. Thornton, and D. A. Shirley, Rosenblatt, R. F. Davis, E. Umbach, A. G. Baca, "Photoelectron Angular Distributions of H2O,1' D. A. Shirley, Y. Huang, W. M. Kang, S. Y. Tong, J. Chem. Phys. 76, 860 (1982); LBL-11822. "Normal Photoelectron Diffraction of 0/Cu(001): A Surface Structural Determination," Phys. Rev. B 3. S. Southworth, W. D. Brewer, C. M. Truesdale, 26_, 7076 (1982); LBL-14188. P. H. Kobrin, D. W. Lindle, and D. A. Shirley, "Photoelectron Angular Distributions from Hg and

D2," J. Elect. Spectros. and Re). Phen. 26, 43 LBL Reports (1982); LBL-12922. 1. C. M. Truesdale, S. Southworth, P. H. Kobrin, 4. J. W. Hepburn, 0. J. Trevor, J. E. Pollard, U. Becker, 0. W. Lindle, and D. A. Shirley, "K- D. A. Shirley, and Y. T. Lee, "Multiphoton Ioniza Shell Auger and Photoelectron Angular Distribu tion Photoelectron Spectroscopy of CC12^2 an{* tion of CO," LBL-12873. CCI3F," J. Chem. Phys. ^6, 4287 (1982); LBL-13752. 2. S. Southworth, U. Becker, C. H. Truesdale, 5. Z. Hussain, E. Umbacb, J. J. Barton, J. G. P. H. Kobrin, 0. W. Lindle, S. Owaki, and D. A. Tabin, and D. A. Shirley, "Angle-resolved Photo- Shirley, "Electron Spectroscopy Study of Inner- emission Study of the Valence Bands of H(011) in Shell photoexcitation and Ionization of Xe," the Photon Energy Range 1100-1260 eV: Observa LBL-13697. tion of Strong Direct Transitions and Phonon Effects," Phys. Rev. B 25, 672 (1982); LBL-12672. 3. J. E. Pollard, "Photoelectron Spectroscopy of Supersonic Molecular Beams," Ph.D. thesis, 6. J. E. Pollard, D. J. Trevor, J. E. Reutt, LBL-14285. Y. T. Lee, and D. A. Shirley, "Rotationally Resolved Photoelectron Angular Distributions for 4. J. J. Barton, C. C. Bahr, Z. Hussain, S. W. »2* {"' = 0) at x « 584 and 736 A," Chem. Pnys. Robey, J. G. Tobin, L. E. Klebanoff, and 0. A. Lett. 88, 434 (1982); LBL-13998. Shirley, "Direct Surface Structure Determination with Photnelectron Diffraction," LBL-14645. 7. 0. A. Shirley, "Surface and Adsorbate Struc tural Studies by Photoemission in the hv = 50- to 5. J. J. Barton and 0. A. Shirley, "High Resolu 5DD-eV Range," CR in Solid State Materials Science tion Fourier Analysis with Autoregressive Linear 12, 373 (1982), LBL-9596. Prediction," LBL-14758. 59 Invited Talks 6. P. H. Kobrin, P. A. Heimann, H. G. Kerkhoff, D. W. Lindle, C. M. Truesdale, T. A. Ferrett, 1. D. A. Shirley, "Photoelectron Spectroscopy: U. Becker, and D. A. Shirley, "Photoelectron The Electron's View of Matter," Chemistry Depart Measurements of the Mercury 4f, 5p and 5d Sub- ment, University of Hawaii, Manoa, May 5, 1982. shells," LBL-14759. 2. D. A. Shirley, "Angle-Resolved and Resonant 7. D. H. Rosenblatt, "High Resolution Electron Photoemission with Synchrotron Radiation," Physics Energy Loss Spectroscopy and Photoelectron Dif Department, University of Hawaii, Manoa, May 6, fraction Studies of the Geometric Structure of 1982. Adsorbates on Single Crystal Metal Surfaces," Ph.O. thesis, i.BL-14774. 3. D. A. Shirley, "New Photoemission Results: Shape Resonances and Photoelectron Diffraction," 8. D. A. Shirley, P. H. Kobrin, D. W. Lindle, Chemistry Department, University of Hawaii, Manoa, C. M. Truesdale, S. Southworth, U. Becker, and May 7, 1982. H. G. Kerkhoff, "Resonance and Threshold Effects in Photoemission Up to 3500 eV," LBL-14857. 4. 0. A. Shirley, "New Interference Phenomena Observed with Photoelectrons," Physical Chennstry 9. D. A. Shirley, "Recent Advances in the Study Seminar, University of California, Berkeley, of Band Structures in Solids by Photoelectron California, October 12, 1982. Spectroscopy," LBL-15040. 5. D. A. Shirley, "Angle-Resolved Photoemission: 10. P. H. Kobrin, S. Southworth, C. M. Truesdale, Extended Fine Structure," Bay Area Surface/ D. W. Lindle, U. Becker, and D. A. Shirley, Interface Technical Meeting, SRI International, "Threshold Measurements of the K-Shell Photo Menlo Park, California, December 9, 1982. electron Satellites in He and Ar," LBL-15042. 6. D. Trevor, "Multiphoton Ionization Photo H. J. G. Tobin, S. W. Robey, and D. A. Shirley, electron Spectroscopy," 1982 March Meeting of the "The Two-Dimensional Valence Electronic Structure American Physical Society, Dallas, Texas, March of a Monolayer of Ag on Cu(001)," L8L-15133. 8-12, 1982.

12. J. G. Tobin, S. W. Robey, L. E. Klebanoff, 7. J. G. Tobin, "Photoemission of Ag Overlayer and D. A. Shirley, "The Evolution to Three- on Cu (001); the Observation of the Transition Dimensional Valence 8and Structure in Ag Over- from 2-3 Dimensionality," Solid State Physics layers on Cu(OOl)," LBL-15134. Seminar, Department of Physics, University of California, Davis, California, October 7, 1982. 13. S. Y. Tong, W. M. Kang, D. H. Rosenblatt, J. G. Tobin, and D. A. Shirley, "Photoeleccron 8. C- C. Bahr, "Fourier Analysis of Photo Diffraction Analysis of the Structure of c(2x2)Q electron Diffraction Data to Determine Adsorbate on Ni(001)," LBL-15152. Structures: c(2x2)S/Ni(100) and p(2x2)S/Cu(100),N Western Regional Meeting of the American Chemical 14. J. G. Nelson, W. J. Gignac, R. S. Williams, Society, San Francisco, California, October S. W. Robey, J. G. Tobin, and D, A, Shirley, 27-29, 1982. "ARPES Investigation of Intrinsic Surface States on the Ge (001; 2x1 Reconstructed Surface," 9. John J. Barton, "Angle-Resolved Photoemission LBL-15250. Extended Fine Structure," Ninth Annual Stanford Synchrotron Radiation Laboratory User Group Meet 15. C. M. Truesdale, S. Southworth, P. H. Kobrin, ing, Stanford, California, October 22, 1982. D. W. Lindle, and D. A. Shirley, "Photoelectron Angular Distributions of the N£0 Outer Valence 10. P. H. Kobrin, "Atomic Photoe'iectron Spec Orbitals in the 19-31 eV Photon Energy Range," troscopy witn Synchrotron Radiation," Atomic LBL-15287. Physics Seminar, University of Virginia, Charlottesville, Virginia, June 22, 1982.

11. P. H. Kobrin, "Photoelectron Spectroscopy cf Gases Using Synchrotron Radiation," Sandia Tech nical Seminar, Sandia National Laboratory, Liver- more, California, December 8, 1982. 160 h. Crossed Molecular Beams*

Yuan T. Lee, Investigator

Introduction. The major thrust of this redistribution of both products also agreed with search project is to unravel the complex dynam statistical calculations. ical processes occurring in chemical reactions. Molecular beams of reactants are used to study This study shows that the abstraction channel individual reactive encounters between molecules begins to compete significantly with the insertion or to monitor photodissociation events in a col channel at higher collision energies. The oxygen lision free environment. which does insert forms a highly excited complex that lives only one rotational period before dis From measurements of the energy and angu sociation. lar distributions of the product fragments, a detailed picture of the reaction mechanism, * * * including prefer.ed orientations of reactants, competition between alternative pathways and fBrief version of LBL-15259. partitioning of energy in the products can be 1. R. Schinke and W. A. Lester, Jr., J. Chem. obtained. Phys. _72> 3754 (1980).

1. 0(1D) + HD REACTIVE SCATTERING* 2. PHOTOEXCITATION STUDIES OF SUBSTITUTED A. Wodtke, R. J. Baseman, and Y. T, Lee CYCLOHEPTATRIENtS

The ![) state of atomic oxygen is a highly R. J. Brudzynski, P. Felder, R. J. Buss, and reactive entity which readily inserts in C-H Y. T. Lee bonds and quenches easily to the ground 3p state. The reaction with H2 occurs with large cross sec An important aspect of unimolecular reactions tion, and one of the surfaces of approacn corre is the collisional energy transfer to and from lates with ground state H2O. Schinke and Lester* the excited mnlecule. The absence of detailed have calculated an ab initio surface fcr the re information about these processes has necessi action and performed trajectory studies on the tated crude assumptions in theoretical treatments surface. They identify two mechanisms, insertion of the effect these processes have on unimolecular c' the oxygen into the H-H bond followed by H reaction rates- We would like to investigate en elimination and collinear attack with rebound of ergy transfer in single collisions with a highly the OH. The insertion pathway has no potential vibrationally excited molecule, and a promising barrier while a small (~3 kcal/mole) barrier ex candidate is the substituted cycloheptatriene ists for collinear approach. (R-CHT). These molecules absorb near uv radia tion, being excited to the S\ state and Earner work in this laboratory with O(lp) + Hp promptly undergo internal conversion to high has shown that insertion is the major reactive vibrational levels of the ground state. Prepara channel at low collision energies. These studies tory to energy transfer studies we have investi have now been extended to 0(*D) + HD in which the gated unimolecular decomposition of excited CHT presence of two channels, forming OH or 0D pro and isopropyl substituted CHT. vides a more sensitive test of the dynamical behavior of the system. The reactive scattering A supersonic jet of the R-CHT was crossed w,is measured with the high resolution, universal with a Nd:YAG laser, and photofragments were cross-molecular beam machine, with a supersonic detected at several angles. The laser/beam jet if 0(*D) producpd in a plasma discharge and interaction region could be translated upstream a jet of HD from a tungsten oven. Angular and from the detector viewing region. The behavior velocity distributions of OH and Of) product were of the product signal as a function of laser measured and these were deconvoluted to produce position can be used to determine the lifetime product energy and center-of-mass angular distri of the excited species. The method is most butions. sensitive to lifetimes in the range 2.0 to 200 usee. Both CHT and isopropyl-CHT were found Both OH and OD pr,duct were found to be back- to have lifetimes less than 2 usee. scattered, pointing to the abstraction mechanism as a significant contribution to the overall re The CHT, which is known to isomerize to action. The ratio of OH to OD product agreed toluene, was found to decay by two channels, well with statistical predictions and the ex yielding H + benzyl and CH3 + phenyl. The pected isotope effect. The translational energy angular distributions of product are shown in Fig. 2.1 together with the statistical calcula tions, which are found to fit reasonably well.

*This work was supported by the Pi'rector, Office The isopropyl-CHT can isomerize to give either of Energy Research, Office of Basic Energy methyl-isopropyl-benzenc, or isobutyl-benzene. Sciences, Chemical Sciences Division of the Two product channels were observed which we at U. S. Department of Energy under Contract No. tribute to formation of CH3 + CH3-C6H4-CHCH3

DE-AC03-76SF00098. and CH(CH3)2 + benzyl. 161

8 m 1.00 " " - PRODUCTS 4000 Q '{ 3000 H + BENZYL 0.75 2000

• CH3* PHENYL > \ \ 1000 \ /r 0 1/5 0.50 P *+ ^ *W«ft z 4000 V, INT E 0.25

1^ 1 1 I ""~~~*"T+--*-. & IOr 15' 20 25' 30c LABORATORY ANGLE Fig. 2.1. Angular distribution of products from KrF excitation of cycloheptatriene. Lines are statistical calculations. Error bars are la. (XBL 824-9135) MASS 30 10' 3. PHOTOCHEMISTRY OF GLYOXAIJ

J. W. Hepburn, R. J. Buss, L. J. Butler, and Y. T. Lee

Glyoxal is a model system for studying molecu lar photophysics and photochemistry. The first excited singlet state has been the subject of many studies, but the photochemistry remains only poorly known. In recent ab initio work by Osamura et al.l it has been proposed that one mechanism 0 50 100 150 20C 250 for decay of Si glyoxal is the three body decom ARRIVAL TIME (^sec) position to give 2C0 + H^ in a concerted fashion Fig. 3.1. Time-of-f1ight spectra taken with de from a near planar transition state. Stimulated tector 10° from the molecular beam. Solid lines by this interesting theoretical work, we have are calculated fits to the data. Contributions used the method of molecular beam photofragment from each channel are shnwr, as dotted lines. translational spectroscopy to measure products of (XBL 826-10473) the unimolecular decay of glyoxal after laser ex citation to the Si state. of Osamura et al. In the mass-28 spectra a third A supersonic jet of glyoxal in a helium seed feature appears as a shoulder- on the larger peak, gas was excited with a NdrYAG pumped dye laser at and this can only arise from the formation of 2C0

4398 A, which is resonant with the band origin of + '•'•z- the 8o band of the Si state. The photofragments were measured with the rotatable mass spectrometer This study has shown unambiguously that the at several angles. In Fig. 3.1 are shown the time- Si state of glyoxal does undergo predissociation of-flight data measured at three masses, 10° from in a collision-free environment. We have found the glyoxal beam. evidence for the occurrence if the three body de composition and for the heretofore unit>.tified Our experimental results show that three dis hydroxymethylene molecule. tinct channels are occurring in this system. From the mass 30 and mass 29 spectra, it is seen that two reaction paths are present, which we attribute to formation of CO + H?00 and CO + HCOH. The lat tBrief vprsion of LBL-15467. ter channel is only slightly exoergic at these 1. Y. 0 jnura, H. F. Schaefer, M. Dupuis, and W. excitation energies according to the calculations A. Lester, Jr., J. Chem. Phys. 7£, 5828 (1981). 162

4. ELASTIC SCATTERING OF ArXe AND KrXeT derived potential gives an excellent fit except for minor disagreement in the region of the R. T. Pack,* J. J- Valentini,* C. H. Becker, R. rainbow angle. This study is the first reported J. Buss, and Y. T. Lee derivation of a multiproperty empirical inter atomic potential for ArXe and KrXe. In a collaborative study with the Los Alamos group, we have obtained elastic differential cross sections for scattering of Ar and Kr by Xe. These have been combined with accurate *Brief version of LBL-H952. viscosity measurements* and second virial ^Permanent address: Los Alamos National Labora coefficient data^ in order to obtain very tory, Los Alamos, NM 87545. accurate interaction potentials. The three 1. J. Kestin, H. E. Khalifa, and W. A. Wakeham, properties used in the fitting are complementary Physica (Utrecht) 90, 215 (1978). for this purpose because the differential cross 2. J. Brewer, TechT Rept AD663448, AFOSR Con section at this collision energy (1.5 kcal/mole) tract No. AF49(638)-1620 (1967), available from is most sensitive to the attractive well part of the Clearinghouse for Federal Scientific and the potential while the viscosity and virial co Technical Information; H. P. Rentschler and B. efficients are most sensitive to the location and Schramm, Ber. Bunsenges Phys. Chem. 81, 319 shape of the repulsive wall. (1977).

The differential cross sections were obtained with the universal cross-molecular beam machine 5. PHOTODISSOCIATION OF LARGE WATER CLUSTERSt in a scattering experiment with supersonic beams of the two rare gases. The interatomic potential M. F, Vernon, R. Page, and Y. T. Lee is an M3SV generalized Morse-spline-van der Waals form. As part of a continuing study of the decompo sition of vibrationally excited water clusters, The experimental differential cross section new measurements have been made of the lifetime, for the Kr-Xe system is shown in (Fig. 4.1) with frequency dependence, and cluster size dependence the solid line shov-ing the calculated fit. The for clusters containing 13-25 water molecules. The reason for the study was to see if the cluster size could become large enough so that the "heat capacity" would enable the cluster to exist vi brationally excited for many microseconds. This idea was stimulated by our previous results which suggested that the geometry for the clusters to predissociate when excited with 10 kcal/mole of energy was far removed from their equilibrium configuration. The energy was then thought to be well distributed among the cluster. By making the cluster larger, the average energy in any one of the hydrogen bonds would be smaller than the bond energy, hence its lifetime would be length ened. The results of the current study showed that even for clusters containing 25 water mole cules, the lifetime is less than 1 microsecond, the minimum time resolution of our apparatus.

+Brief version of LBL-11970.

6. INFRARED MULTIPHOTON DISSOCIATION OF t C2F5CL AND C2F5Br

D. Krajnovich, A. Giardini-Guidom", P. Schulz, Aa. Sudbo, F. Huisken, Z.Zhang, Y. R. Shen, and Y. T. Lee

Preliminary results of experiments on the in 0 B 16 24 32 40 48 56 frared multiphoton dissociation of C2F5CI were * (deg) presented in an earlier Annual Report.* A few 0 years ago more detailed measurements on C2F5CI Fig. 4.1. KrXe laboratory differential scatter- were made using a high repetition rate CO? laser. ing. The solid line is the calculated result; CgFgBr was also studied for comparison purposes. the points are from the present experiment. Un The analysis of the new data has now been com certainties of a few representative points are pleted. In the case of C2F5CI, competition is shown. The arbitrary units here are chosen to observed between the two lowest energy Jissocia- correspond to square angstroms per steradian. tion channels: C-Cl and C-C bind fission. The (XBL 8212-12538) higher energy C-C channel accounts for approxi- 163

mately 20% of the dissociation yield at an energy 1982 PUBLICATIONS AND REPORTS fluence of 0.6 J/cmz, increasing to 60% at 10 J/cm2. Our earlier conclusion* concerning the Refereed Journals presence of a small exit barrier for the C-C fis sion reaction appears to be incorrect because of til. Carl C. Hayden, Daniel M. Neumark, Kosuke a background modulation effect in the data meas Shobatake, Randal K. Sparks, and Y. T. Lee, ured at small angles. In the case of CgFsBr, the "Methylene Singlet-Triplet Energy Splitting by only primary reaction observed is Br atom elimin Molecular Beam Photodissociation of Ketene," J. ation, in agreement with statistical expectations Chem. Phys. .76, 3607 (1982). for this molecule. For both C2F5CI and CgFsBr, secondary dissociation of C2F5 primary product to £§2. Pauline Ho, Douglas J. Bamford, Richard J. CF3 + CFg during the COj laser pulse is observed Buss, Yuan T. Lee, and C. Bradley Moore, "Photo- at high energy fluences. In the case of the Cl- dissociation of Formaldehyde in a Molecular Beam," and Br-atom elimination reactions of C2F5CI and F Br J. Chem. Phys. 76, 3630 (1982); LBL-13438. C2 5 » deviations from simple RRKM translations! energy distributions are observed at low recoil energies (<0.15 kcal/mole). These deviations *3. J. w. Hepburn, D. J. Trevor, J. E. Pollard, result from the requirement to conserve angular D. A. Shirley, and Y. T. Lee, "Multiphoton Ioni momentum during the dissociation. zation Photoelectron Spectroscopy of CCI2F2 and CCI3F," J. Chem. Phys. 76, 4287 (1982); LBL-13752.

* * * 4. Yuan T. Lee, "Molecular Beam Studies of Bi-

molecular Reactions: F + H2 and Li + HF," Ber. tBrief version of LBL-15354. Bunsenges. Phys. Chem. 86, 378 (1982); LBL-1371?. 1. HMRD Annual Report 1978, LBL-10000, pp. 473-477. 5. J. E. Pollard, D. J. Trevor, J. E. Reutt, Yuan T. Lee, and D. A. Shirley, "Rotationally Resolved Photoelectron Angular Distributions for Hg (v'=0) at x = 584 and 736 A," Chem. Phys. Lett. 88, 434 (1982); LBL-13998. 7. MOLECULAR BEAM STUDIES OF VIBRATIONAL PREDIS-

SOCIATION OF (C2Hfl)2 AND (NH3)2 USING A PULSED C02 6. J. E. Pollard, D. J Trevor, Y. T. Lee, and LASER1" D. A. Shirley, "Rotationally Resolved Photoelec tron Spectroscopy of n ••H?, P-H2, HD, and D2,'1 J. D. Krajnovich, P. Schulz, Aa. Sudbo, Y. R. Shen, Chem. Phys. 77, 34 (K.82); LBL-13696. and Y. T. Lee §7. M. F. Vernon, D. J. Krajnovich, H. S. Kwok, In April 1979 we carried out some experiments J. M. Lisy, Y. R, S'len, and Y. T. Lee, "Infrared on the vibrational predissociation of (C2Hfl)2 and Vibrational Predis^ociation Spectroscopy of Water (NH3)2 using a high repetition rate CO2 laser. In Clusters by the Crossed Laser-Molecular Beam both cases efficient vibrational predissociation Technique," J. Chem. Phys. 77, 47 (1982); is observed between 930-980 cm-*. The lineshapes LBL-11970. for the predissociation yield measured at a laser energy fluence of 0.6 J/cm^ are not symmetrical. 8. F. A. Houle, S. L. Anderson, D. Gerlich, T. The products of the ^H^JJJ and {NH3J2 predissoci Turner, and Y. T. Lee, "Nonadiabaticity in Ion- ation reactions are formed with a mean recoil en Molecule Reactions: Coupling of Proton and Charge ergy of 0.25 and 0,23 kcal/mole, respectively. Transfer in the HjS and D£ + Ar System," J. Chem. The distribution of product recoil energies is Phys. .77, 1842 (1982); LBL-13638. roughly exponential in both cases. For both reactions the predissociation yield exhibits a 9. S. L. Anderson, T. Turner, B. H. Mahan and Y. very weak dependence on the laser power over a T. Lee, "The Effects of Collision Energy and Ion 100-fold range. Complete saturation of the pre Vibrational Excitation on Photon and Charge Trans dissociation yield is not achieved at our highest z fer in HjS + N2, CO, 02," J. Chem. Phys. 77, 1842 energy fluences of ~2 J/cm . These results sug (1982); LBL-13556. ~" gest that: (i) only one photon (-2.7 kcal/mole) is involved in the predissociation reaction for (^3)2 as well as (C2H4)2; (ii) the predissocia 10. Piergiorgio Casavecchia, Guozhong He, Randal tion yield lineshape is inhomogeneously broadened; K. Sparks, and Yuan T. Lee, "Rare Gas-Halogen Atom Interaction Potentials from Crossed Molecular

''"Brief version of LBL-15354. §12. M. F. Vernon, J. M. Lisy, D. J. Krajnovich, 1. M. P. Casassa> 0. S. Bomse, and K. C. Janda, A. Tramer, H. S. Kwok, Y. R. Shen, and V. T. Lee, J. Chem. Phys. 74, 5044 (1981). "Vibrational Predissociation Spectra and Dynamics 164

of Small Molecular Clusters of HgO and HF," Far 7. Yuan T. Lee, "Reaction of Oxygen Atoms with

aday Disrussion Mo. 7$t Van der Waals Molecules, Unsaturated Hydrocarhons," International Symposium St. Catherine's College Oxford, England, April on Chemical Kinetics Related to Atmospheric Chem 5-7, 1982, to be p»blisned; LBL-13740. istry, Tsubuka Science Center, Tsubuka, Japan, June 6-10, 1982. 13. J. E. Pollard, D. J. Trevor, Y. T. Lee, and D. A. Shirley* "Rotational Relaxation in 8. Yuan T. Lee, "Molecular Beam Studies on Ele Supersonic Beams of Hydrogen by High Resolution mentary Reactions and Photochemical Processes," Photoelectron Spectroscopy," J. Chem. Phys. 2Z.» Symposium on Reaction Dynamics, Institute for 4818 (1982); LBL-14279. Molecular Sciences, Okazaki, Japan, June 12, 1982. 14. R. T. Pack, 0. J. Valentini, C. H. Becker, R. J. Buss, and Y. T. Lee, "Multiproperty Empiri 9. Yuan T. Lee, "Molecular Beam Research at cal interatomic Potentials for ArXe and KrXe," J. Berkeley," Institute for Molecular Sciences, Chem, Phys. 77, 5475 (1982); LBL-14952. Okazaki, Japan, June 14, 1982.

15. D., Krajnovich, F. Huisken, Z. Zhang, Y. R. 10. Yuan T. Lee, "Recent Advances in Reaction Shen, and Y. T. Lee, "Competition Between Atomic Dynamics," Institute of Chemistry, Beijing, and Molecular Chlorine Elimination in the Infrared China, June 22, 1982. Multiphoton Dissociation of CF^Cl?," J. Chem. Phys. 7]_, 5977 (1982); LBL-14478. 11. Yuan T. Lee, "Primary Photochemical Proc esses," Institute of Chemistry, Beijing, China, 16. F. Huisken, D. Krajnovich, Z. Zhang, Y. R. June 23, 1982. Shen, and Y. T. Lee, "Competing Dissociation Chan nels in the Infrared Multiphoton Decomposition of 12. Yuan T. Lee, "Molecular Beam Studies of Reac Ethyl Vinyl Ether," J. Chem. Phys., submitted July tion Dynamics," Institute of Chemical Physics, 1982. Dalien, China, June 25, 1082.

13. R. J. Buss, "Molecular Beam Study of Glyoxal LBL Reports Predissociation ^rom the Si State," 15th In formal Conference on Photochemistry, Stanford 1. Carl Clay Hayden, "Molecular Beams Studies of University, Stanford, California, June 27-July 1, the Energetics and Dynamics of Elementary Chemical 1982. Reactions," Ph.D. thesis, LBL-13660. 14. Yuan T. Lee, "Molecular Beam Investigation on 2. Robert J. Baseman, "Crossed Molecular Beams Laser Chemistry," Department of Chemistry, Fudan Reactive Scattering of Oxygen Atoms, Ph.D. thesis, University, Shanghai, China, June 28, 1982. LBL-16259. 15. Yuan T. Lee, "The Use of Vacuum UV Photons in the Investigation of Energetics and Dynamics of Invited Talks Elementary Reactions," University of Taiwan, Taiwan, July 14-30, 1982. 1. Yuan T. Lee, "Molecular Beam Chemistry," Chinese Institute of Engineers Annual Meeting, 16. Carl C. Hayden, "F + Hg Reactive Scattering San Francisco, California, January 30, 1982. Experimental Results," Gordon Research Conference on Atomic and Molecular Interactions, New London, 2. Yuan T. Lee, "Dynamic Resonance Phenomena on New Hamsphire, July 25-30, 1982. Reactive Scattering," Department of Chemistry, University of California, Irvine, California, 17. R. J. Buss, "The Study of High Energy Colli March 8, 1982. sions in Molecular Beams," 11th International Hot Atom Chemistry Symposium, University of Californ 3. Yuan T. Lee, "Vibrational and Translational ia, Davis, California, August 16-21, 1982. Energy Dependence in Reactions >jf H^," American Chemical Society Meeting, Las Vegas, Nevada, March 18. Yuan T. Lee, "Molecular Beam Studies on Reac 30-April 1, 1982. tion Dynamics," XI International Chemical Kinetics Symposium, Gftttingen, West Germany, August 22-27, 4. R. J. Buss, "0(3P) Reactions with Unsatu 1982. rated Hydrocarbons, Mechanism and Dynamics," American Chemical Society Symposium, Chemical 19. Yuan T. Lee, "Molecular Beam Studies of Kinetics of Combustion, Las Vegas, Nevada, March Primary Photochemical Processes of Organic 28-April 1, 1982. Molecules," Department of Chemistry, Harvard University, Cambridge, Massachusetts, September 5. Yuan T. Lee, "Molecular Beam Studies of 29, 1982. Reaction Dynamics," Department of Chemistry, University of Indiana, Indianapolis, Indiana, 20. Yuan T. Lee, "Molecular Beam Photofragmenta- April 22, 1982. tion Studies of Simple Polyatomic Molecules," Wayne State University, October 11, 1982. 6. Yuan T. Lee, "Molecular Beam Studies of Reaction Mechanism and Photochemical Processes," 21. Yuan T. Lee, "Primary Photochemical Processes Department of Chemistry, University of Pittsburgh, of Polyatomic Molecules," Annual Meeting of Cana Pittsburgh, Pennsylvania, Hay 19, 1982. dian Physicists Association, Division of Atomic 165 and Molecular Physics, University of Alberta, Alberta, Canada, October 22-23, 1982. tpartially supported by the Office of Naval Research under Contract No. NO0014-75-CO671. 22. Yuan T. Lee, "Molecular Beam Studies of Primary Photochemical Processes of Organic ^Partially supported by the National Science Molecules," Department of Chemistry, University Foundation. TC :IuK/ 3uEI huUL u+ CM Utah, December 7, 1982. ^Partially supported by the Assistant Secretary for Nuclear Energy, Office of Advanced Systems 23. Yuan T. Lee, "Molecular Beam Chemical Kinet and Nuclear Projects, Advanced Isotope Separation ics," Golden Jubilee of Chinese Chemical Society, Division, U. S. Department of Energy under Con Taipei, Taiwan, China, December 12, 1982. tract No. DE-AC03-76SF00098. 166

i. Potential Energy Surfaces lor Chemical Reactions* Henry F. Schaefer HI, Investigator

Introduction. This research program has two of LBL theoretical studies in this area was to goals—related yet distinct. The first goal is understand why the bridging methylene is apparent the development of new theoretical and/or compu ly favored over the terminal structure. tational methods for the description of "what electrons are doing in molecules," to use the words of Robert S. Mulliken. Specifically, the The metal dimer-methylene system MgCHz is the single outstanding problem in the field is the simplest that can in principle display both ter correlation problem, that of formulating models minal M-M-CHg and bridging 'or going beyond the single-particle or Hartree- Fock i.^oroximation. The second goal of our re CH, search :•• to apply these theoretical methods to / N significant pi,->blems of broad chemical interest. M H Currently two 6"eas are of special concern: (1) 1 geometrical structures. Having previously studied model theoretica studies of chemisorptian, metal the terminal Al-CH, A1-CH2, and A1-CH3 metal- clusters, and organometallic species and (2) po organic fragment species, the AI2CH2 system was tential energy surf&Lt: '..at govern gas-phase chosen to allow a competition between the terminal chemical reactions. Research in the former area and bridged structures. Nonenpirical molecular is ultimately aimed at a truly molecular under electronic structure theory was used, with double standing of catalysis, a subject pertinent to zeta (DZ) and DZ + polarization basis sets in future energy requirements, but sometimes conjunction with both s^'if-consistent-f ield (SCF) approached by trial and error methods. In the and configuration interaction (CI) methods. Among latter area our research sometimes tends toward structures considered (see Fig. 1.1), the bridging molecules potentially important in interstellar arrangement, with the space, atmospheric chemistry, and the development of high power laser systems. It is to be empha sized that in recent years theoretical chemistry has become a significant source not only of broad /\ generalities, but also of specific predictions Al Al concerning molecular systems that may be very and CH2 planes perpendicular to each other, important but inaccessible to experiment. lies lowest energetically. For this structure the Al-Al distance is 3.61 A\ the Al-C distance 2.00 A, and the methylene bond angle 105.5°. The completely planar structure, found by twisting 1. TERMINAL VS BRIDGE BONDING OF METHYLENE TO the methylene group 90°, is predicted to lie 31 kcal higher, but has a much shorter Al-Al dis METAL SYSTEMS, A12CH2 AS A MODEL SYSTEM^ tance, 3.03 A. The terminal structure lies 46 Douglas J. Fox and Henry F.Schaefer III kca? above the absolute minimum on the energy

surface and has re(Al-Al) = 2.87 A, re(Al-C) = The first mononuclear transition metal 1.81 A, and a methylene bond angle of 112.2 . methylene complex, Cp2TaCh3CH2» was synthesized All of the above structures are closed-shell by Schrock in 1975. However, during the interven singlets in their lowest electronic states, but ing seven years, only one other terminally bonded the nnergies of several triplet species are also neutral methylene complex, the TpzZrfPPhzMejCH;? discussed. The Al-C bond energy for the terminal molecule of Schwartz, has been reported. The structure is 81 kcal, in good agreement with that very first transition metal methylene complex predicted (77 kcal) earlier by comparable methods reported in the literature was not a terminal for AICH2. However, for the bridging A^CHg, the structure at all but rather the oridged molecule Al2-.

The weight of the evidence would appear to suggest that bridging transition metal methylene complexes are going to be far more prevalent than tLrief version of LBL-14339; J. Chem. Phys., the analogous terminally bound species, The goal press.

which are known from experiment. Our theoretical 1.065, methods predict that CH3O* lies 4.9 kcal mol-1 1.974 higher in energy than CH2OH* with a barrier to rearrangement to CHjOH* of 36.9 kcal mol-1. Rearrangement of CH30H' to CH2OH* via a H dissociation-recombination mechanism is energeti cally more costly (by 6.1 kcal mol-1). The Jahn- Teller distortion of CH3O" from point group C^ H is described in some detail. Barriers to inver 1.083/ sion and rotation in CH2OH* are predicted and

A|| 2.8Z3 ^ ,.^/j,,^ 3^ compared with the results of :ISR experiments. Finally the dissociation of CH3O* and CH2OH' to yield formaldehyde plus H' art1 each predicted to involve modest reverse activation energies.

H fBrief version of LBL-15495; J. Chem. Phys., in press. ^Present address: Research School of Chemistry, Australian National University, Canberra, Australia.

3. CYCLIC D HEXAAZABENZENE—A RELATIVE MINIMUM H _3™L H 6h ON THE N6 POTENTIAL ENERGY HYPERSIJRFACE?'

Paul Saxe and Henry F. Schaefer III

The well-known German physical organic chemis1. Vogler has recently reported laboratory evidence for the formation of hexaazabenzene from photo chemical elimination in cis-diazidobis (triphenyl- phosphorane) platinum(Il). As evidenced by U.c news article in the May 24, 1982 edition of "hemical and Engineering News, this finding has attracted widespread attention. Previous theoret ical studies have suggested that the 05^ benzene- 3.606 like structure is not a minimum on the Ng poten tial energy hypersurface. Here the Ng problem Fig. 1.1. Theoretical molecular structures for has been addressed at the self-consistent-field various conformations and electronic states of (SCF) level of theory using double zeta (DZ) and

Al2Ch2. (XBL 821-3545A) double zeta plus polarization (DZ+P) basis sets. The smaller set yields the prediction that the

D5n structure is a transition state connecting two equivalent bond alternant N5 equilibrium geometries. A second transition state for dis 2. THE WEAKLY EXOTHERMIC REARRANGEMENT OF METHOXY sociation to three nitrogen molecules (which are RADICAL (CH30') TO THE HYDROXYMETHYL RADICAL energetically much lower than N5) was also + located. Contrary to previous theoretical work (CH OH*) 2 hexaazabenzene is found to be a minimum at the highest completely consistent level of theory. Svein Saebo,* Leo Radom,* and Henry F. Schaefer The equilibrium geometry occurs for re(N-N) = HI 1.288 ft, a bond distance suggesting that N5 is c classic aromatic molecule. The transition Although the CH3O* dnd CH2OH' radicals have state to 3N2 lies 10.3 kcal higher and has the long been considered critical intermediates in planar bond alternant structure ri(N-N) = 1.178 combustion and atmospheric processes, only very A, r?(N-N) = 1.551 A. Harmonic vibrational recently has the potential significance of the frequencies for hexaazabenzene are predicted with isomerizat ion CH3O" * CH2OH* been appreciated. both theoretical methods and demonstrate that the This isomerization and related aspects of the energy surface is very flat with respect to bond CH30'/CH20H" potential surface have been studied alternating Bgu displacements. The inclusion using ab initio molecular electronic structure of correlation effects lowers the barrier to N5 theory with moderately large basis sets and with dissociation when geometrical structures obtained incorporation of electron correlation. The vibra at the SCF level of theory are assumed. Figure tional frequencies of CH3O*, CH20H", and seven 3.1 summarizes the theoretical predictions. other stationary points on the potential energy hypersurface have been predicted, both to compare with results from spectroscopy and to provide estimates of zero-point vibrational corrections. In general, there is reasonable agreement with those vibrational frequencies of CH3O- and ^OH* +Brief version of LBL-15156; J. Am. Chem. Soc, in press. 168

5. P. Saxe, D. J. Fox, H. F. Schaefer, and N. C. Handy, "The Shape-Driven Graphical Unitary Group Approach to the Electron Correlation Problem. Application to the Ethylene Molecule," J. Chem. Phys. 77, 5584 (1982); LBL-14093.

6. P. Saxe, Y. Yamaguchi, and H. F, Schaefer, "Analytic Second Derivatives in Restricted Kartree-Fock Theory: A Method for High-Spin Open-Shell Molecular Wave Functions," J. Chem. Phys. 77, 5647 (1982); LBL-14408. r(N-N), longer (&) —- Other Publications

1. H. F. Schaefer, "Quantum Chemistry," Encyclopedia of Science and Technology, 5th edition, McGraw-Hill, New York, 1982, p. 164.

LBL Reports 1. D. J. Fox and H. F. Schaefer, "Terminal vs. Bridge Bonding of Methy-ene to Metal Systems.

A12CH2 as a Model System," LBL-14339. 2. G, Fitzgerald, P. Suxe, and H. F. Schaefer, "Singlet CyclobLtyne: A Relative Minimum on the C4H4 Potential Energy Hypersurface?" LBL-14622.

3. P. Saxe and H. F. Schaefer, "Cyclic 0^ —£ r (N-N), longer |A) Hexaazabenzene—A Relative Minimum on the N5 Potential Energy Hypersurface?" LBL-15156. Fig. 3.1. Qualitative sketches of the potential

energy surface connecting Dgn hexaazabenzene with 4. W. D. Laidig and H. F. Schaefer, "Electronic three infinitely separated N2 molecules. As a Symmetry Breaking in Polyatomic Molecules. one-dimensional reaction coordinate, the longer of Multiconfiguration Self-Consistent-Field Study of the two distinct N-N distances ^n D^h% was the Cyclopropenyl Radical, C3H3," L8L-14G92. chosen. Of course, the two N-N distances coalesce as one passes from 03k to Dfih point group. 5. Y. Yamaguchi, J, F. G?W, and H. F. Schaefer* (X6L 826-3914) "Molecular Clustering About A Positive Ion. Structures, Energetics, and Vibrational Frequen cies of the Protonated Hydrogen Clusters H$, HJ,

H}9 and Hg"," LBL-15154.

6. S. Sfebo, L. Radom, and H. F. Schaefer, "The Weakly Exothermic Rearrangement of Methoxy Radical (CH3O ) to the Hydroxymethyl Radical (CHjOH )," 1982 PUBLICATIONS AND REPORTS LBL-15495.

Refereed Journals 7. M. R. Hoffmann, Y. Yoshioka, and H. F. Schaefer, "Vibrational Frequencies for Sila- 1. M. A. Vincent and H.F. Schaefer, "Isomeric acetylene and rts Silylidene and Vinylidene Structures of C^LiF, the Prototype Carbenoid," Isomers," LB1-14312. J. Oiem, Phys. T7_, 6103 (1982); LBL-13785. 8. J. Bicerano, H. F. Schaefer, and W, H. 2. Y. Osamura, Y. Yamaguchi, P. Saxe, M. A. Miller, "Structure and Tunneling Dynamics of Vincent, J. F, Gaw, and H. F. Schaefer, "United Malonaldehyde, A Theoretical Study," LBL-15155. Theoretical Treatment of Analytic First and Second Enerqy Derivatives in Open-Shell Hartree- 9. P. S. Bagus, H. F. Schaefer, and C. W. Fock Theory/ Chemical Physics 72, 131 (1982); Bauschlicher, "The Convergence of the Cluster LBL-15165. Model for the Study OT Chemisorption: Be3sH, LBL-15496. 3. H. f. Schaefer, "The Silicon-Carbon Double Bond: A Healthy Rivalry Between Theory and 10. W. D. Laidig and H. F. Schaefer, "Where to Experiment," Accounts of hem. Res. JJi* 283 Look for the Electronic Spectrum of Hydrogen Iso- (1982); LBL-14276. cyanide. Hi.:," LBL-14203.

4. M. A. Vincent, Y. Yoshioka, and H. F. 11. K. S. Kim, H. F. Schaefer, L. Radom, J. A. Schaefer, "High Spin Electronic States of the Pople, and J. S. Binkley, "Vibrational Frequen Experimentally Observed Molecular Ions MnCHj and cies Of the HCCN Molecule. A Near Degeneracy CrCHJ," J. Phys. Chem. 86, 3905 (1962); Between Bent Cyanocarhene and Linear Allene- LBL-14287. Related Geometries,' LJL-15166. 169

12. G. Fitzgerald and H. F. Schaefer, "Struc Department of Chemistry, Harvard University, tures, Energetics, and Vibrational Frequencies of Cambridge, Massachusetts, May 17, 1982. Cyclopropyne," LBL-]D888. Lester P. Kuhn Memorial Lecturer, Department of Chemistry, Johns Hopkins University, Baltimore, 13. H. A. Vincent, H. F. Schaefer, A. Schier, Maryland, May 18, 1982. and H. Schmidbauer, "The Molecular and Electronic Chemistry Division, Argonne National Laboratory, Structure of Phosphonium Cyclopropylide H3P = Argonne, Illinois, May 19, 1982.

C(CH2)2: A Theoretical Study," L8L-15399. Department of Chemistry, Ohio State University, Columbus, Ohio, May 20, 1982. Department of Chemistry, California Institute of Technology, Pasadena, California, May 25, 1982. Gordon Research Conference on High Temperature Invited Talks Chemistry, Tilton, New Hampshire, July 29, 1982. 1. H. F. Schacfer, "The Third Age of Quantum Chemistry," presented at the following places: 2. P. Saxe, "Capabilities of the Shape-Driven Symposium on Theoretical Organic Chemistry/ Graphical Unitary Group Approach," Theoretical Computational Quantum Chemistry, Canberra, Chemistry Group, Los Alamos Scientific Labora Australia, February 1?, 1982. tory, Los Alamos, New Mexico, August 1982. Research School of Chemistry, Australian National University, March 1982. 3. H. F. Schaefer, "Analytic Energy Second Deriv Department of Theoretical Chemistry, University atives in Molecular Electronic Structure Theory," of Sydney, Australia, March 1982. Symposium on Transition States in Chemistry, Department of Chemistry, University tf Nevada, American Chemical Society, Kansas City, Missouri, Reno, Nevada, April 30, 1982- September 15, 1982 and Department of Chemistry, Department of Chemistry, University of California, University of Hawaii, Honolulu, Hawaii, December Irvine, May 3, 1982. 17, 1982. 170 3. Atomic Physics

a. Atomic Physics*

Richard Marrus, Investigator

1. PARITY VIOLATION IN ATOMS'*" magnetic dipole decay (HI). Because exact calcu lations can be performed for one-electron atoms, E. Commins and P. Drell the measurement of the lifetime of the 2 'Sj/^ state is a very rigorous test of the theory of During the past year we completed construction these decays. of the apparatus and carried out a careful theo retical and experimental study of possible sources Figure 2.1 shows the theoretical1-3 and experi of systematic error in parity measurements. We mental^ decay rates scaled by Z-^ of the 2 *Suz have found, and dealt with, the two main sources state of the hydrogen isoelectronic sequence. Tn& of trouble. These are: decrease in the 2E1 rate shown in Fig. 2.1 is be cause of ralativistic corrections, which at Z - 18 (a) Misaligned magnetic field combined with are 1.1%. The upper curve shows the contribution small residual nonreversing components of electric of the Ml rate. Our measurement of the 2 2Sito field. By carrying out parity measurements with lifetime in hydrogenlike argon of 3.487 (0.036) the magnetic field deliberately misaligned by a ns, in agreement with the theoretical value of large amount, we have demonstrated that this ef 3.497 ns, is the first experiment to see the fect is small and can be corrected for adequately. presence of the Ml component. It is marginally sensitive to the relativistic correction to the (b) Electric field sign-dependent background 2E1 rate. that varies with linear polarization of laser light. This is a subtle effect that we discovered The lifetime of the 2 2Sj/£ state was measured the explanation only after many weeks of difficult by the beam-foil time-of-flight technique. The investigation. It arises because of photoelectron extremely small error is a reflection of our ejection from tantalum electrodes in the cell by understanding of the systematic effects in this scattered laser light. These electrons are accel experiment, including cascades from higher excited erated in the electric field and excited thallium states, interference from the spectra of helium atoms to fluoresce. The small background thus like ions, collisions in the residual gas, and the created depends on the sign of the electric field effects of spectator electrons. and the light polarization, and can thus create a false parity effect. The solution to this problem is to replace tho tantalum electrodes with new electrodes (nickel} with a short wavelength photo

electric threshold \0 < \, where A is our laser wavelength. This is now being done. Meanwhile, KCN CCM&M we have made numerous improvements in apparatus %2 ,15 US sensitivity and have also isolated and treated J various other small sources of systematic error. 8.8 We remain confident that a precise measurement Prior CCMBM -4-2EI Ml . can be carried out in the very near future. — £EI r 8.0 j HCN 7.6

S " + ,n 8rief version of LBL-15510. 7.2 £ T 2. ONE PERCENT MEASUREMENT OF THE LIFETIME OF Z 4 6 8 10 12 W 16 IS STAT E 0F THE 2 2s1/2 HYDROGENLIKE ARGON (Z = 18)+ z—* Pirv*y Gould and Richard Marrus Fig. 2.1. Comparison of experimental and theo retical 2 2Si/2 decay rates of hydrogenlike atoms. '•he ? 2Si/2 state is the only metastable state All decay rates have been divided by Z&. Theory . the hydrogen isoelectronic sequence. It decays is from Ref. 4, and the experimental points are by simultaneous emission of two electric dipole MS, Ref. 5; CCMBM, Ref. 6; HCN, Ref. 7; Prior, photons (2E1) and by single-photon relativistic Ref. 8; and KCN, Ref. 9. (XBL 832-8350)

obtained, which can be written in the form y - * * * «JV> n + YO» where is the velocity-averaged i'Brief version of LBL-15649. capture cross section, n is the gas density, and

1. S. P. Goldman and G. W. F. Drake, Phys. Rev. T0 is the loss rate resulting from processes A 24, 183 (1981). independent of gas density. The quantity 2- W. R. Johnson, Phys. Rev. Lett. 29, 1123 can be extracted from the measured rate constants (1972). "~ by making a linear plot of y vs n and taking the 3. F. A. Parpia and W. R. Johnson, Phys. Rev. A slope. An effective cross section is obtained by 26, 1142 (1982). dividing by the root-mean-square velocity of 37 S. Klarsfeld, Phys. Lett. 30A, 382 (1969). the ions in the trap. This is possible because 5. R. Marrus and R. w". Schmied"er, Phys. Rev. A the virial theorem for the logarithmic potential 5, 11670 (1972). present in a cylindrical trap shows V^s to be "6". C. L. Cocke, B. Curnutte, J. R. Macdonald, independent of the ion orbit. J. A. Bednar, ana R. Marrus, Phys. Rev. A 9, 2242 (1974). Results for the effective cross section shows 7. E. A. Hinds, J. E. Clendenin, and R. Novick, that at fixed velocity there are very strong Phys. Rev. A 17, 670 (1978). oscillations with the ion charge q. This is 8. M. H. Prior, Phys. Rev. Lett. _29, 611 (1972). indicative of a resonance capture process where 9. C. A. Kocher, J. E. Clendenin, and R. Novick, electron transfer can take place only if the Phys. Rev. Lett. 29, 615 (1972). binding energy in the state in which capture occurs equals the ionization potential. An un usual feature of our data is that some of the 3. ELECTRON CAPTURE BY LOW-ENERGY HULTICHARGED charge states exhibit very strong velocity de NEON I0NS+ pendences while, for the same velocity range, cross sections for other charge states are Richard Marrus, Michael Prior, and C R. Vane velocity insensitive. This differs from data taken by other experiments at higher energies. Capture of electrons by multicharged ions at thermal and subthermal energies is an important * * * process in fusion devices and the interstellar medium. In fusion devices, it can lead to "''Brief version of LBL-15720. serious energy losses resulting from electron capture and subsequent radiation. As a result, many studies of this process have been carried 198? PUBLICATIONS AND REPORTS out with ions in the energy range > 100 q/eV, where q is the charge. These studTes have Refereed Journals employed a variety of iO;i sources, notably EBIS devices and ECR sources. The results at these 1. R. Mann, C. L. Cocke, A. S. Schlachter, energies yield cross sections which vary slowly M. Prior, and R. Marrus, "Selective Final State with energy and are mainly monotonic in q. Population in Electron Capture by Low-Energy, Highly Charged Projectiles Studied by Electron- In order tz extend these measurements to lower Gain Spectroscopy." Phys. Rev. Lett. 49, 1329 energies, we have employed as an ion source the (1982). — recoil ions produced when a fast beam from an accelerator traverses a low-density gas. The 2. H. Goula and J. Alonso, "Charge, Changing energies of these recoil ions is quite low, Cross Sections for Pb and Xe Ions at Velocities typically about l-2xq eV. These ions are then Up to 4 x 109 cm/sec," Phys. Rev. A 26, 1134 confined in an electrostatic ion trap where they (1982). — can undergo charge capture collisions with the neutral atoms present in the gas. Detection of 3. R. Marrus, M. Prior, and C. R. Vane, "Electron the ions is done with a commercial quadrupole Capture by Trapped Low-Energy Multicharged Neon mass analyzer and a channeltron detector. By Ions," Nucl. Instrum. Meth. 202, 171 (1982). monitoring the ion density as a function of time after the accelerator pulses, the exponential 4. L. Hunter, E. Cummins, and L. Roesch, decay that results from electron capture is "Measurements of Spontaneous-Emission Rates in observed. From this decay a decay constant y is Atomic Thallium," Phys. Rev. A 25, 885 (1982). 172 4. Chemical Energy

a. Formation of Oxyackte ol Suifurfrom S02* Robert E. Connick, Investigator

Introduction. The primary goal of the re from HSO3-, one corresponding to ca. 20% and the search is to investigate the fundamental chemis other ca. 80%. It seems likely that these two try of sulfur dioxide, as well as species formed signals correspond to the two isomers of bilsul- from it, in aqueous solution. There is strong fite ion: one with the proton bonded tc the sul interest currently in this chemistry because of fur and the other with the proton bonded to an the pernicious effects of acid rain, formed when oxygen. While the existence of the two isomers sulfur containing fuels, such as coal, are burned has been postulated for some time and Raman evi and the gaseous products are allowed to escape dence has been obtained for their presence in into the atmosphere, with the ultimate formation solution, this would be the first time that such of sulfuric acid. Initially combustion forms direct evidence was found and a measure of their sulfur dioxide. The best way currently to con abundance obtained. Experiments are under way to trol acid rain is to remove the sulfur dioxide from the stack gases of coal-burning power plants try to detect the proton resonance of the less with aqueous scrubbers. Thus, the chemistry of labile species, which presumably is the one with sulfur dioxide and the species formed from it at the proton attached to the sulfur. low acidity is vital to the understanding and de sign of these massive installations. In addition 2. RATES OF SUBSTITUTION REACTIONS ON METAL IONS the aqueous chemistry of sulfur dioxide is im Robert E. Connick and Michael R. Wagner portant when it escapes into the atmosphere, as it is believed that the oxidation to sulfuric Work in progress. Rates at which substitution acid occurs in water films on suspended dust takes place of ligands coordinated to metal ions particles. have yielded a wealth of information on the me chanisms of such reactions, particularly in recent A secondary and not closely related goal is to years. Yet the factors controlling the lability determine the factors controlling the rate of of such ligands are still incompletely understood. substitution reactions in the first coordination The present work is aimed at trying to resolve sphere of metal ions. These reactions are im the relative importance of ionic, electronic, and portant in almost all processes involving metal steric effects using a single metal ion, Ni'4", ions in solution. This includes metal ion com partially complexed by a variety of ligands, and plex formation, some oxidation-reduction reac by measuring the exchange rate of the attached tions, as well as many biological processes water molecules. A comparison of iminodiacetate involving metal ions. with methyl iminodiacetate is under way.

1. THE RATE AND MECHANISM OF EXCHANGE OF OXYGENS Computer simulation of an exchange reaction on BETWEEN BISULFITE ION AND WATER a metal ion is being written for publication with Dr. Berni Alder. Robert E. Connick and David A. Horner Work in progress. When sulfur dioxide dis 1982 PUBLICATIONS AND REPORTS solves m water, it retains its molecular struc ture as SOg, rather than hydratiny to H2SO3. On Refereed Journals ionization to bisulfite ion and hydrogen ion, it must react with a water molecule. The forward 1. R. E. Connick, T. M. Tarn, and E. von Deuster, "Equilibrium Constant for the Dimerization of and reverse of the ionization reaction lead to 2 exchange of the oxygens of bisulfite ion and Bisulfite Ion to Form S3O5 -," Inorg. Chem. 21, water. It is believed that this is the dominant 103 (19B2); LBL-12272. mechanism for oxygen exchange. The two studies reported in the literature are in strong dis 2. I. Nagypa*!, I. Fabia*n, and R. E. Connick, agreement as to the rate. "NMR Relaxation Studies in Solution of Transition Metal Complexes, VII: Protonation of the Vanadyl In the present study the nuclear magnetic res Ion in Aqueous Solution," Acta. Chimica Academiae onance signal of oxygen-17 is being used to mea Scientiarum Hungaricae 110(4), 447 (1982). sure the exchoiige rate. The results so far are in agreement with one of the earlier studies as 3. R. E. Connick and T. G. Braga, "Kinetics of to rate, but appear to be yielding further in the Oxidation of Bisulfite Ion by Oxygen," ACS sights on the reaction. In the pH region around Symposium Series, No. 188, edited by J. L. Hudson 4, two oxygen-17 signals are observed arising and G. T. Rochell, 1982, p. 153-171; LBL-13259. Invited Talks *This work is supported by the Director, Office of Energy Research, Office of Basic Energy Sci 1. Robert E. Connick, "Computer Modeling of Sol ences, Chemical Sciences Division of the U.S. vent Exchange in the First Coordination Sphere of Department of Energy under Contract No. Metal Ions," Stanford University, Palo Alto, Chem DE-AC03-76SF00098. istry Department Seminar, January 12, 1982. 173

b. Catalytic HyrogmMtfon of CO: CaMyafs on WaH-Characterlzad Surtacaa*

Gabor A. Somorjai, Investigator

and

Catalyst* by Supported Metaia*

Alexis T. Bell, Investigator

Introduction. The purpose of this program is to develop an Understanding of the fundamental 1. C. S. Kellner and A. T. Bell, J. Catal. 67, processes involved in catalytic conversion of 175 (1931). ~~ carbon monoxide and hydrogen to gaseous and liquid fuels. Attention is focused on defining the factors that limit catalyst activity, selec 2. THE EFFECTS OF ADDITIVES ON THE Fe AND Re tivity, and resistance to poisoning, and the CATALYZED CO HYDROGENATION REACTIONS relationship between catalyst composition/ structure and performance. To meet these objec E. L. Garfunkel, J. Parmeter, and G. A. Somorjai tives, a variety of surface diagnostic techniques (LEED, AES, XPS, EELS, IRS, TPD) are used to Rhenium and iron foils have been studied as characterize supported and unsupported catalysts model Fischer-Tropsch catalysts in a high before, during, and after reaction. The informa pressure/low pressure apparatus. In addition to tion thus obtained is combined with detailed the clean metal surfaces, the effects of K, Na, studies of reaction kinetics to elucidate reac and 0 "promoters" and C and S "poisons" were tion mechanisms and the influence of modifica examined to learn more about the role of surface tions in catalyst composition and/cr structure additives. on the elementary reactions involved in carbon- monoxide hydrogenation. Using a 4:1 ratio of H2:C0 at 2 atm total pressure, activation energies for the production of methane were found to be 24 (Fe) and 28 (Re) kcal/mol. At 520 K, clean rhenium produced -95% 1. THE HYDROGENATION OF CO OVER RHODIUM FOIL, methane and -5% Cj (ethylene, ethane, pro AND RHODIUM COMPOUNDS, FeRh0 and Na2Rh0 pylene...), while clean iron produced -80% methane 3 3 and -20% CJ. On rhenium, submonolayers of Na M. Logan and G. A. Somorjai lowered the methanation rate and changed the selectivity to ~QQ% methane and ~20% Cj- On The hydrogenation of carbon monoxide has been iron the presence of alkali (Na or K) decreased studied over rhodium foil and rhodium-containing the overall rate. The changes in selectivity refractory oxides. We have determined product varied according to the degree of oxidation of the distributions, turnover frequencies, and activa substrate and alfcali overlayer, usually favoring tion energies for the reaction. We have found an c£ "ith alkali present. inverse deuterium effect on the rhodium foil, like that found on ruthenium by Kellner and Belli Oxidation of the rhenium surface, on the other with Rate(D2)/Rate(H?) * 1.4. The partial ires- r hand, increased both the total rate of reaction sure dependence of the reaction rate has al o and the selectivity toward methane (~98&). The been determined. For a -ate law of the form same effect was observed on iron surfaces. The

P th increased methanation rate upon oxidation was Rate = kP£o H » ® values x = -1 and y = +1 mainly because of an increased surface area as were obtained. The activation energy does not de monitored from CO thermal desorption peak area. pend on the total pressure of the reactant gases, The activation energies for the production of but it changes with the CO to H2 partial pressure ethylene were lower than those for methanation on ratio. This change in activation energy implies both surfaces. a change in the rate-determining step of the reaction. The cause for catalyst poisoning on both Fe and Re surfaces was found to be the irreversible Preliminary studies of rhodium oxides have build up of a "graphitic" carbon overlayer. Sul been performed on Na2Rh03 and FeRh03. The NagRh^ fur was also a poison, and it enhanced the rate was found to produce mainly alkanes and some of carbon build up during the reaction. Auger alkrnes and oxygenated molecules while FeRh03 and thermal desorption spectroscopies were used formed methane and alkenes (mainly ethene and to analyze the surfaces before and after propene) almost, exclusively. reactions.

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sci ences, Chemical Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. 174

3. THE PRODUCTION OF METHANOL FROM CO MO H2 5. THE INFLUENCE OF METAL-SUPPORT INTERACTIONS OVER THORIUM OXIDE CATALYST SURFACES ON THE SYNTHESIS OF METHANOL OVER PALLADIUM

J. Maj, C. Colmenares, and G. A. Somorjai R. F. Hicks and A. T. Bell

These studies are being carried out in the In a previous investigation, it was shown that Lawrence Livermore Laboratory where there are metal-support interactions strongly influence the extensive facilities for handling actinide ele activity and selectivity of Pd for the synthesis ments and their compounds that include thorium of methanol from CO and Hg. The present study oxide. High surface area oxide was synthesized was undertaken to elucidate the manner in which a fay precipitating thorium carbonate and then heat support influences Pd c«ialysts. . To date, the ing slowly up to 400'C. CO2 and toO are driven work has focused on determi ring the kinetics of off and the oxide with about 10 m^/gm area is methanol and methane synthesis over a series of produced. silica and lanthanum oxide-supported Pd catalysts. For a given set of reaction conditions, Pd/La203 Using a microreactor in the flow-mode,the catalysts exhibit methanol turnover frequencies CO/Hj reaction is carried out at 50 atm total ten to twenty times greater than those observed pressure and in 1:2 and 2:1 gas ratios. Under for Pd/Si02 catalysts. Quite surprisingly, the these conditions methanol is produced almost^ kinetics of methanol synthesis ?.re virtually the exclusively in the temperature range 250-350"C, same for silica and lanthanum oxide-supported Pd. with an ogtimum turnover frequency at 325*C. This equivalence is expressed by the close simi Above 400 C the catalyst slowly deactivates. larity of the activation energi 5 and the power law dependencies on Hj and CO partial pressures. Substantial differences occur, though, in the kinetics of methane synthesis on the two types of catalyst. The effects of metal dispersion on the specific activities for methanol synthesis are 4. CHARACTERIZATION OF CARBON DEPOSITS FORMED also different on the two supports. On silica, DURING CO HYDROGENATION OVER RUTHENIUM the specific activity is nearly independent of dispersion, whereas on lanthanum oxide the spe P. Winslow and A. T. Bell cific activity increases with increasing disper sion. For both supports, tha specific activity Transient response mass spectrometry and for methane synthesis increases monotonically Fourier-Transform infrared spectroscopy were used with decreasing dispersion. to study the nature of carbon species present on the surface of a silica supported ruthenium cata lyst during Fischer-Tropsch synthesis. Carbon The physical characteristics of Pd/Si02 and was found to exist on the catalyst surface as Pd/Ld203 are being determined through the use of linearly adsorbed CO and two forms of nonoxygen- XPS, infrared spectroscopy of adsorbed CO, and TPD ated carbon. The integrated absorption coeffi spectroscopy of adsorbed Hg and CO. Infrared cient of the linear adsorbed CO was determined by spectra of adsorbed CO indicate that the princi isotope dis1 .cement and found to be nonlinear pal planes exposed by supported Pd are 100 and with coveraijj. The two forms of nonoxygenated 111. For Pd/La203, CO adsorption is observed on carbon, a and e, were distinguished by their both 100 and 111 planes, the proportion depending relative reaction rates during titration of the on the dispersion of Pd. For Pd/SiOg, CO adsorp catalyst surface with deuterium. The a-carbon tion occurs primarily on 100 planes. Correlation was found to be very reactive and appears to be of the observed rate data with the infrared obser the primary form involved in Fischer-Tropsch syn vations for Pd/LajOs suggests that the 111 planes thesis. The B-carbon is much less reactive than of Pd are a factor of two less active than the 100 the a-carbon. It was established that under planes. helium flush, the $-carbon is gradually converted to the a-carbon. 1982 PUBLICATIONS AND REPORTS The influence of reaction conditions on the amounts of each carbon species was studied at Refereed Journals 473 K; the surface coverage by CO was independent of either CO or H2 partial pressure and corre 1. E. L. Garfunkel, J. E, Crowell, and G. A. sponded to about 0.9B of a Ru monolayer. The Somorjai, "The Strong Influence of Potassium on a-carbon coverage did not exceed 0.02 of a mono the adsorption of CO on Platinum Surfaces: A TDS layer, was independent of time for a given set of and HPEELS Study," J. Chem. Phys. 86, 310 (1982); conditions, and increased with increasing O2 pres LBL-13349. sure or decreasing CO pressure. By contrast, the B-carbon coverage increased monotonically in time, 2. M. Langell and G. A. Somorjai, "The Composi grohing to about 0.10 of a monolayer after 5 hr. tion and Structure of Oxide Films Grown on the The accumulation of e~carbon accelerates with in (110) Crystal Face of Iron," J. Vac. iu. Technol, creasing CO partial pressure. 21, 858 (1982); LBL-13203. 175

3. W. McLean, C. A. Colmenares, R. L. Smith, and 5. A. T. Bell, "Studies of the Mechanism and G. A. Somorjai, "Electron Spectroscopy Studies of Kinetics of Hydrocarbon Formation During Fischer- the Clean Thorium and Uranium Surfaces. The Tropsch Synthesis Over Ruthenium," Sohio Research Chemisorption and Initial Stages of Reaction with Center, Cleveland, Ohio, March 1982.

02, CO, and C02," Phys. Rev. B 25(1), 8 (1982); IJCRL-86167. 6. A. T. Bell, "Synthesis of Oxygenated Compounds from CO and H2," Sohio Research 4. P. R. Watson and G. A. Somorjai, "The Forma Center, Cleveland, Ohio, March 1982. tion of Oxygen-Containing Organic Molecules by the Hydrogenation of Carbon Monoxide Using a 7. A. T. Bell, "Fischer-Tropsch Synthesis Over- Lanthanum Rhodate Catalyst," J. Catal. 74, 282 Ruthenium. Studies of Reaction Mechanism, Kinet (1982); LBL-12969. ics, and Effects of Metal Dispersion," Central Research & Development Department, E. I. duPont 5. P. R. Watson and G. A. Somorjai, "The de Nemours & Co., Wilmington, Delaware, April Interactions of CO, CO2, and O2 with Rhodium 1982. Oxide (RH203'5HpO): Its Reduction tnd Cata lytic Stability," J. Phys. Chem. 86, 3993 (1982); 8. A. T. Bell, "The Role of CHx(x . 1-3) Species LB, -13524. in Fischer-Tropsch Synthesis," Symposium on Advan ces in Catalytic Chemistry II, Salt Lake City, 6. N. W. Cant and A. T. Bell, "Studies of Carbon Utah, May 1982. Monoxide Hydrogenation Over Ruthenium Using Transient Response Techniques," J. Catal. _73, 257 9. A. T. Bell, "Studies of the Mechanism of CO (1982); LBL-12598. Hydrogenaeion," First International Summer School on Advanced Coal Technologies, Cosenza, Italy, 7. C. S. Kellner and A. T. Bell, "Effects of July 1982. Dispersion on the Activity and Selectivity of Alumina-Supported Ruthenium Catalysts for the 10. A. T. Bell, "Mechanism and Kinetics of Hvdrogenation of Carbon Monoxide," J. Catal. 75, Fischer-Tropsch Synthesis Over Ruthenium 2S1 (1982); LBL-12429. — Catalysts," Engler-Bunte Institut, Universitat Karlsruhe, Karlsruhe, Germany, July 1982. 8. J. A. BaJcer and A. T. Bell, "Hydroslation of Carbon Monoxide Over Ruthenium. Detection of 11. A. T. Bell, "Mechanism and Kintics of Fischer- Surface Species by Reactive Scavenging," J. Catal. Tropsch Synthesis Over Ruthenium Catalysts," 78, 165 (1982); LBL-i3773. Institut fur Physikalische Chemie, Universitat Munchen, Mlinchen, Germany, July 1982. LBL Reports 12. A. T. Bell, "Applications of Fourier-Transform

1. A. T. Bell, "The Role of CHx(x = 1-3) Species Infrared Spectroscopy to Studies of Adsorbed Spe in Fischer-Tropsch Synthesis," LBL-14503. cies," Gordon Conference on Vibrational Spectros copy, Wolfboro, New Hampshire, August 1982. Other Publications 13. A. T. Bell, "Effects of Metal-Support Inter 1. A. T. Bell and L. L. Hegedus, "Catalysis actions on the Synthesis of Methanol over Palla Under Transient Conditions," ACS Symposium Series dium," China-Japan-USA Symposium on Heterogeneous 178, Am. Chem. Soc, Washington, D.C., 1982. Catalysis, Dalian, People's Republic of China, September 1982. Invited Talks 14. A. T. Bell, "Studies of CO Hydrogenation over 1. G. A. Somorjai, "Catalyzed Hydrogenavion of Supported Metal Catalysts," Department of Chemis Graphite and CO. Photocatalyzed Surface Dro- try, Nanjing University, People's Republic of cesses," Fudan University, Shanghai, China. China, September 1982. April 1982. 15. A. T. Bell, "Temperature Prograrmied Desorption 2. G. A. Somorjai, "Catalyzed Hydrogenation of of H2 and NO from a Rh/SiO? Catalyst. Determina Carbon Monoxide," Jilin University, Changchun, tion of Rate Parameters," 184th National Meeting China, April 1982. of the ACS, Kansas City, Missouri, September 1982.

3. A. T. Bell, "Fischer-Trops."h Synthesis Over 16. A. T. Bell, "Synthesis of Hydrocarbons and Ruthenium. A Case Study in the Analysis of Oxygenated Products Over Ruthenium and Palladium," Reaction Mechanisms," Research L'ivision, W. R. Department of Chemical Engineering, University of Grace & Co., Columbia, Maryland, January 1982. Minnesota, Minneapolis, Minnesota, October 1982.

4. A. T. Bell, "Fischer-Tropsch Synthesis Over 17. A. T. Bell, "Studies of Surface Reactions Ruthenium Catalysts," Tarrytown Technical Center, Under Transient Conditions Using Fourier-Transform Union Carbide Corp., Tarrytown, New York, March Spectroscopy," Annual AIChE Meeting, Los Angeles, 1982. California, November 1982. 176

c. Organometalllc Chemistry of Coal Convtrtlon* K. Peter Vollhardt, investigator

Introduction. The purpose of this work is to This reaction constitutes a new homogeneous model develop organic and organometallic methodology for C-C bond-forming and bond-breaking on sur concerned with furthering tiie understanding of faces. basic processes in coal conversion and related catalytic reactions. These include studies on the mechanism of the Fischer-Tropsch and other C-C bond forming reactions, the synthesis of homogeneous analogs of surface intermediates in the reduction of carbon monoxide, the crganome- tallic activation of thiophene with respect to sulfur extrusion, and the construction of novel binuclear transition metal complexes in order to establish their potential catalytic and stoichio metric chemistry.

1. BISCARBYNE CLUSTERS AS HOMOGENEOUS ANALOGS OF FISCHER-TROPSCH INTERMEDIATES ON SURFACES1"

Neal T. Allison,* John R. Fritch,§ David E. Van Horn,11 K. Peter C. Vollhardt, and Eric C. Walborsky

Biscarbyne clusters are being investigated as potential mimics of surface species thought to be '''Brief version of 0. Chem. Soc, Chem. Comm., 203 intermediates in Fischer-Tropsch reactions and (1982), LBL-13759, and of LBL-15413 and LBL-15414. the skeletal rearrangement of hydrocarbons as ^Present address: Dept. of Chemistry, University observed in platforming. This work should lead of Arkansas. to a better understanding of catalysis on sur ^Present address: Celanese Corporation, Corpus faces, the design of better catalysts, and the Christi, TX. discovery of new catalytic reactions* ^Present address: Dept. of Chemistry, Texas A & H University, College Station, TX. The approach used relies on the ready synthetic accessibility of trinuclear cobalt biscarbyne clusters reported by the Principal Investigator 2. TRANSITION METAL f^.DIATED THERMAL EXTRUSION in 1980. Work has been completed concerning the OF SULFUR DIOXIDE FROM THIOPHENE-1,1 DIOXIDES'1' potential nucleophilic character of these systems, which has led to the discovery of novel chemistry James S. Orage and K. Peter C. Vollhardt at the apical carbon, including hydrogen-deuter ium exchange reactions that can be considered as CpCo-r|4-2,5-dimethylthiophene-l,l-dioxide 3 models for such exchange processes on surfaces. was prepared by irradiation of the free heterocy- cle in the presence of CpCo(C0)2» Flash vacuum The x-ray crystallographic analysis of the pyrolysis leads solely to CpCo-n4-l,2,-dimethyl- parent compound reveals a crystal lographic 03!* cyclobutadiene 4 by SO2 extrusion. A crossover symmetry in the solid state with both experiment has shown that the complexes stay in u3fi*-bonded carbyne ligands lyincyclobutadienes, but only partially equilibrated starting materials. The While exploring the chemistry of the double observed data suggest as a reasonable mechanism deck cluster 1, an unprecedented rearrangement metal insertion into the thirphene ring followed was uncovered involving the simultaneous coupling by SO2 extrusion involving a deinsertion path and decoupling of carbyne fragments (1 —> 2). way.

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sci ences, Chemical Sciences Division of the U.S. Department of Energy under Contract No. 0E-ACQ3-76SFQ0098. 177

+4. B. C. Bern's and K. P. C. Vollhardt, "An Approach to Tricyclo[8.4.0.Dl,>7]-tetradecahepta- 1,3,5,7,9,11, 13-ene (benzo[l,2-a]cyclobuta[l,2- £]cyclooctatetra-ene): Unusual flfermal Rearrange ments in the C^Hin-Manifold," Tetrahedron 38, 2911 (1982).

*5. R. A. Earl and K. P. C. Vollhardt, "On the Synthetic Utility of Thermally Generated Imines: The Retro-ene Imino Diels-Alder Reaction," Hetero- cycles 19, 265 (1982).

+6. E. D. Sternberg and K. P. C. Vollhardt, "Co +Brief version of Organometallics 1, 1545 (1982), balt-Mediated r_2+2+2]Cycloadditions En Route to LBL-14977. Natural Products: A Novel Total Synthesis of Steroids Via the One-Step Construction of the B,C,D-Framework from an A-Ring Precursor," 0. 3. WORK iN PROGRESS Org. Chem. 47, 3447 (1982).

The scope and limitations of the reaction of +7. W. V. Dower and K. P. C. Vollhardt, "The trinuclear cobalt biscarbyne clusters with sulfur Thermal Conversion of 1,5,9-Triynes to Aromatic that leads to cluster degradation and the forma Compounds: [2+2-*-2]Cycloadditions or Sigmatropic tion of metalladithiolanes are being explored. Rearrangements?" Angew. Chem. 34, 712 (1982); Crossover-labeling experiments have shown that Angew. Chem., Int. Ed. Engl. 217 685 (1982); this reaction involves intramolecular carbyne- Angew. Chem. Suppl., 1545 (198?). carbyne coupling. 8. J. S. Drage, R. A. Earl, and K. P. C. A facile entry into fulvaiene dinuclear metal Vollhardt, "Deoxygenation of Allylic Carbinol- complexes has been found. Several complexes have amides and Related Alcohols by Acidic Sodium been analyzed by x-ray crystallography. Prelimi Cyanoborohydride: Scope and Limitations," J. nary investigations have led to the discovery of Heterocyclic Chem. W, 701 (1982). new organometallic transformations. Fulvalenedi- ruthenium tetracarbonyl has been shown to undergo +9. J. P. Tane and K. P. C. Vollhardt, "Cyclo- a photolytic (sunlight) isomerization to a new pentadienone Complexes as Synthons: Ring- and dinuclear cluster in which both the SP2-SP2 bonds Regiospecific Nucleophilic Additions to Cobalto- of the fulvaiene ligand as well as the metal-metal cinium Salts. Synthesis of Substituted Cyclo- bond have been cleaved. This process has been pentadienes and Cyclopentenones," Angew. Chem. shown to be thermally reversible, thus constitut 94, 642 (1982); Angew. Chem., Int. Ed. Engl. 21, ing a novel potential photochemical storage cycle. W7 (1982); Angew. Chem. Suppl., 1360 (1982).-

The chemistry of fulvalenedimolybdenum hexacar- +10. B. C. Berris, Y.-H. Lai, and K. P. C. bonyl is being investigated. Vollhardt, "A Cobalt Catalyzed Biphenylene Synthesis," J. Chem. Soc., Chem. Commun., 953 Exploratory work is concerned with synthetic (19B2). approaches to bisvinylidene complexes. 11. J. S. Drage and K. P. C. Vollhardt, "Thermal Extrusion of Sulfur Dioxide from (I>5_CJHE)CO-I,4- 1982 PUBLICATIONS AND REPORTS thiophene-l,l-dioxides: A New Organometallic Rea ction," Organometallics I, 1545 (1982); LBL-14977. Refereed Journals +12- W. V. Dower and K. P. C. Vollhardt, "Mechan 1. K. P. C. Vollhardt, "Cobalt Mediated Bond ism of the Isomerization of 1,5,9-Cyclododeca- Forming and Bond Breaking Reactions: Synthetic triyne to Hexaradialene: 1,2:3,4:5,6-Tricyclobu- and Mechanistic Perambulations," Chem. Aust. 49, 3 tabenzene Is Not an Intermediate," J. Am. Chem. (1982); LBL-13997. Soc. 1£4, 6878 (1982).

2. D. E. Van Horn and K. P. C. Vollhardt, "Some LBL Reports Remarkable Reactions of the Biscarbyne Clusters 1 5 f^ni-CRl] [u3n -CR2][n -C5H5)C0]3 with Electro- 1. V. W. Day, D. E. Horn, and K. P. C. philes," J. Chem. Soc, Chem. Cotimun. 203 (1982); 1 5 Vollhardt, "The Structure of [u3i, -CHj2[n -C5H5Co]3, LBL-13759. a Biscarbyne Cluster Derived by the Triple Bond Cleavage of Ethyne," LBL-15413. +3. D. J. Brien, A. Naiman, and K. P. C. Vollhar.'t, "Catalytic Co-Cyclisation of 2. N. T. Allison, J. R. Fritch, K. P. C. a,»-Cyanoalkynes With Alkynes: A Versa Vollhardt, and E. C. Walborsky, "An Unprecedented tile Chemo- and Regioselective Synthesis of Biscarbyne Cluster Rearrangement Involving Simul 2,3-Substituted 5,6,7,8-Tetrahydrtiquinolines taneous Coupling and Decoupling of Carbyne Frag and Other Cycloalka[l,2-b]pyridines," J. Chem. ments: A New Homogeneous Model for C-C Bond- Soc, Chem. Commun. 133 T1982). Forming and Bond-Breaking on Surfaces," LBL-15414. 178

Invited Talks Metals," University of Nice, Nice, France, June 1, 1982. 1. K. P. C. Vollhardt, "Transition Metal Medi ated [2+2+2]Cycloadditions: A Better Version of 13. K. P. C. Vollhardt, "Total Synthesis of Nat the Diels-Alder Reaction?" University of Minne ural Products Using Transition Metal Catalysts sota, Minneapolis, St. Paul, Minnesota, January and Reagents," Plenary Lecturer, Groupe d'Etudes 13, 1982. de Chimie Organometallique, He des Embiez, France, May 31-June 4, 1982. 2. K. P. C. Vollhardt, "Transition Metal Medi ated Carbon-Carbon Bond Formation," Iowa State 14. K. P. C. Vollhardt, "Biscarbyne Clusters as University, Ames, Iowa, January 14, 1982. Potential Homogeneous Models of Surface Species," Invited Lecturer, Second Homogeneous Catalysis 3. K. P. C. Vollhardt, "Mechanistic Investiga Research Conference^ Department of Energy, Uni tions in Cobalt Mediated Carbon-Carbon Bond-Making versity of Wisconsin, Madison, Wisconsin, June and Bond-Breaking Reactions," Hoffmann-LaRoche 7-9, 1982. Incorporated, NJtley, New Jersey, January 25, 1982. 15. K. P. C. Vollhardt, "Transition Metals in Organic Synthesis," Plenary Lecturer, Second 4. K. P. C. Vollhardt, "Transition Metal Catal China-Japan-USA Organometallic and Inorganic yzed Routes to Natural Products," North Jersey Chemistry Seminar, Shanghai, China, June 14-18, ACS Organic Chemistry Section, New Jersey, 1982. January 25, 1982. 16. K. P. C. Vollhardt, "Transition Metal Medi 5. K. P. C. Vollhardt, "Enyne Cyclizations in ated Routes to Natural Products," Universite Organic Synthesis," UC Irvine, Irvine, California, Louis Pasteur, Strasbourg, France, September 6, February 8, 1982. 1982.

6. K. P. C. Vollhardt, "Cobalt Mediated Cycliza 17. K. P. C. Vollhardt, Invited Lecturer (five tions in Organic Synthesis," University of West lectures), Utah Organometallic Chemistry Work Virginia, Morgantown, West Virginia, March 23, shop, Department of Chemistry, University of 1982. Utah, Salt Lake City, Utah, September 20-24, 1982.

7. K. P. C. Vollhardt, "Cobalt Mediated Cycliza- 18. K. P. C. Vollhardt, "Transition Metals in tions in Organic Synthesis," Bucknell University, the Total Synthesis of Natural and Unnatural Lewisburg, Pennsylvania, March 24, 1982. Products," Indiana University, Bloomington, Indiana, October 20, 1982. 8. K. P. C. Vollhardt, "Transition Metal Medi ated [2*2+2] Cycloadditions," Pennsylvania State 19. K. P. C. Vollhardt, "Remarkable Rearrange University, University Park, Pennsylvania, March ments in the Coordination Sphere of Transition 26, 1982. Metals," Indiana University, Bloomington, Indiana, October 21, 1982. 9. K. P. C. Vollhardt, "Remarkable Bond-Making and Bond-Breaking in the Coordination Sphere of 20. K. P. C. Vollhardt, "Transition Metal Catal Transition Metals," ACS Midland Section, Midland, yzed Routes to Natural and Unnatural Products," Michigan, April 13, 1982. Technische Hochschule Darmstadt, Darmstadt, West Germany, December 16, 1982. 10. K. P. C. Vollhardt, "Transition Metals in Total Synthesis," Pfizer Incorporated, Groton, 21. K. P. C. Vollhardt, "Transition Metal Catal Connecticut, April 15, 1982. ysis in Organic Synthesis," University of Marburg, Marburg, West Germany, December 17, 1982. 11. K. P. C. Vollhardt, "Transition M?tal Medi ated [2+2+2] Cycloadditions: A Better Version of the Diels-Alder Reaction?" DuPont Central Re search, Wilmington, Delaware, April 16, 1982. * * * 12. K. P. C. Vollhardt, "Remarkable Rearrange "^Supported in part by NIH. ments in the Coordination Sphere of Transition •Supported in part by NSF. 179

d. Synthetic ind Physical Chwntetry*

William L Jolly, Investigator

Introduction. The purpose of this project is However, for R * OCH3 and R . (((0)3)2, the core to use photoefectron spectroscopy to determine binding energies of the rCo(C0)3]3 cluster are the nature of the bonding 1n significant inorgan significantly lower than expected. These data, ic and organometallic compounds. By measuring and a combination of UPS and XPS data for the core electron binding energies of appropriate chloro and bromo compounds, indicate that groups transition metal compounds, it is possible to such OCH3, N(CH3)2, c1> aml Br act as * donors study the interaction of metal d electrons with toward the C[Co(CO)3]3 system. Binding-energy various ligands and to identify various modes of data indicate that the CH groups of HC[Co(C0)3]3 ligand-metal bonding that have analogs in the in and (HC)2[Co(C0>3]2 are negatively charged, with termediates of catalyzed organic reactions. Core the CH group of HC[Co(C0)3]3 more negative than binding energies can also be used, in conjunction those of (HC)2[Co(C0)3]2. The significantly lower with valence shell ionization potentials, to binding energies of [Co(C0)3]4 reflect the fact quantify the bonding or antibonding character of that three of the carbonyl groups in this compound molecular orbitals. are bridging.

1. AN X-RAY PHOTOELECTRON SPECTROSCOPIC STUDY OF 1 +Brief version of Organometallics 1, 699 (1982); THE c- AND n-ALLYL GROUPS " LBL-13320. A. J. Ricco, A. A. Bakke, and H. L. Jolly 3. AN X-RAY PHOTOELECTRON SPECTROSCOPY STUDY OF From a comparison of the atomic core binding TRANSITION METAL u-METHYLENE COMPLEXES AND energies of CH Mn(C0) , (n-C3H )Mn(C0)5, 3 5 7 RELATED COMPOUNDS* (o-C3H5)Mn(C0)5, and Mnj(CO)io, we conclude that the methyl, propyl, and c-allyl groups in the first three compounds are negatively charged. S. F. Xiang, H. W. Chen, C. J. Eyermann, M. L. Both the carbon Is binding energies and theoreti Jolly, S. P. Smit, K. H. Theopold, R. G. Bergman, cal considerations indicate an unusually large W. A. Herrmann, and R. Pettit relaxation energy associated with the ionization of the terminal carbon atom of the o-allyl group. Gas-phase core electron binding energies have been determined for [Fe(CO)4] CH , [CpMn(C0)2] CH , The H-C3H5 group in (ir-C3H5Mn(C0)5 has a rela 2 2 2 2 tively low electron density, undoubtedly because (CpCoCO^CHj, (CpRhC0)2CH2, and several structur it is a formal 3-electron donor group. The ally related compounds. The binding-energy data carbon Is data indicate that the C5H5 group in indicate that the CH2 groups in the 11-CH2 com {n5C5H5)MnfC0)5 is probably positively charged. plexes are highly negatively charged, especially in the manganese, cobalt, and rhodium compounds. Data for Fe(C0)4C2H4 indicate that the CH2 groups in this compound are negatively charged but less so than in the p-CH? compounds. Data for "Brief version of Organometallics 1, 91 (1982); Fe3(C0)i2 suggest the presence of both terminal LBL-12912. and bridging carbonyl groups.

2. AN X-RAY PHOTOELECTRON SPECTROSCOPIC STUDY OF THE BONDING IN (ALKYL1DYNE)TRIC08ALT NONACARBONYL tBrief version of Organometallics 1, 1200 (1982); COMPLEXES AND RELATED COMPOUNDS* LBL-14069. S. F. Xiang, A. A. Bakke, H. W. Chen, C. J. Eyermann, J. L. Hoskins, T. H. Lee, D. Seyferth, H. P. withers, Jr., and W. L. Jolly 4. JUSTIFICATION OF THE APPROXIMATION THAT SHIFTS IN NONBONDING VALENCE ORBITAL IONIZATION POTENTIAL ARE EIGHT-TENTHS OF SHIFTS IN CORE The core electron binding energy of the BINDING ENERGY* methylidyne carbon atom in RC[Co(C0)3]3 compounds is a function of the electronegativity of the R group. The core binding energies of the W. L. Jolly and C. J. Eyermann [Co(C0)3]3 cluster generally change similarly, but to a smaller extent, with changing R group. Empirical and theoretical data are cited to support the approximation that shifts in strictly nonbonding valence orbital ionization potential are eight-tenths of corresponding shifts in core binding energy. This approximation is shown to be useful in the quantification of the bonding and antibonding character of molecular orbitals. *This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division of the U.S. Department of Energy under Contract No. tBrief version of J. Phys. Chem. 86, 4834 (1982); 0E-AC03-76SF00098. LBL-14532. — ISO

5. WORK IN PROGRESS 4. W. L. Joly and C. J. Eyermann, "Justification of the Approximation that Shifts in Nonbonding We have just completed an XPS study of Valence Orbital Ionization Potential are Eight- volatile iron cluster compounds and a combined Tenths of Shifts in Core Binding Energy," J. XPS/UPS study of the nanqanese pentacarbonyl Phys. Chem. 86, 4834 11982); LBL-H532. halides. We are investigating the nature of the interactions of ethylene with the d orbitals of 18L Reports the iron atom in the complex FetCOJaC^H^. 1. W. L. Jolly, "The Use of Core Binding Energies in the Assignment of the Ultraviolet Photoelectron Spectra of the Manganese Penta 1982 PUBLICATIONS AND REPORTS carbonyl Halides," LBL-15161.

Refsreed Journals 2. D. B. Beach, J. L. Hosfcins, W. L. Jolly, S. P. Smit, and S. F. Xiang, "A Gas-?!:-«e XPS Study 1. A. J. Ricco, A. A. Bakke, and W. L. Jolly, of Iron Cluster Compounds," LBL-147yS "An X-Ray Phutoelectron Spectroscopic Study of the o- and u-Allyl Groups." Organoraetallics 1, 94 Invited Talks (1982); LBL-12912. 1. W. L. Jolly, "The Study of Organometallic 2. S. F. xiang, A. A. Bakke, H. W. Chen, C. J. Compounds by X-Ray Photoelectron Spectroscopy," Eyermann, J. L. Hoskins, T. H. Lee, D. Seyferth, Secoiii Homogeneous Catalysis Research Conference, H. P. Withers, Jr., and W. L. Jolly, "An XPS Madison, Wisconsin, June 7-9, 1982. Study of the Bonding in Alkylidynetricobalt Nonacarbonyl Complexes and Related Compounds," 2. W, L. Jolly, "Photoelectron Spectroscopy and Organoretallics 1, 699 (1982); LBL-13320. Inorganic Chemistry," Seminar at San Francisco State University, Chemistry Department, November 3. S. F. Xiang, H. W. Chen, C. J. Eyennann, 5, 1982. W. L. Jolly, S. P. Smit, K. H. Theopold, R. G. Bergman, W. A. Herrmann, and R. Pettit, "An *PS 3. W. L. ,?olly, "Core Binding Energies Aid the Study of Transition Metal ii-Methylene Complexes Interpretation of Valence Photoelectron Spectra," and Related Compounds," Organometallics 1, 1200 Symposium at American Chemical Society Meeting, (1982); LBL-14069. El Paso, Texas, December 1-3, 1982. e. Chemistry and Morphology of Coal UquefscHon*

Heinz Heinemann, Investigator, with Alexis T. Bell, James W. Evans, Richard H. Fish, Alan V. Levy, Eugene £. Petersen, Gabor A. Somor/ai, Theodore Vermeulen, and K. Peter Vollhardt, Investigators

(See Fossil Energy Section)

t. Electrochemical Systems*

John Newman, Investigator

1. MATHEMATICAL MODELING AND OPTIMIZATION OF where L^B is the length of the protruding elec LIQUID-JUNCTION PHOTOVOLTAIC CELLS* trode assembly, t is the thickness of the protrud ing e>etrode assembly, G is the halfwidth of the Mark E. Orazem and John Newman slot in the semiconductor assembly, and h is the separation between the electrode a-.d the upper The liquid-junction photovoltaic cell is an insulating wall. electrochemical system with semiconducting elec trodes. This system has been extensively studied The mathematical model w»s used to calculate as a means of converting solar energy to electri the effect of cell design on the performance of cal and chemical energy. an n-type GaAs semiconducting anode in contact

with an 0.8 M K2Se, 0.1 H KjSe2, 1.0 H KOH elec A mathematical model of the liquid-junction trolytic solution. The maximum power density of photovoltaic cell was coupled with primary the slotted-electrode cell is presented in Fig. .resistance calculations to predict the optimal 1.2 as a function of LAB'"- Tne optimal value performance of a photoelectrochemical cell with a for Lafi/h was 4, the maximum power density was slotted-semiconductor electrode. The cell resist 47.8 w7m?, and the maximum power efficiency was ance is a function of three geometric ratios, 5.4%. At maximum power the current density was chosen to he t/G, h/G, and Lfljj/h {see Fig. 1.1), 15 mA/cm? delivered at 477.6 i»V. -r T T

Gloss 100- Semiconductor- 5SS55SSS5ICE -Uujr- Currenl Collector- S .80 h= 0.5cm Counterelectrode

Gloss 3 Semiconductor-^c^ ^^ ^^ Current Collector^S SHDHS Electrolyte Counterelectrode -H^^^s\NX\SNNS^^^ ft) Fig, 1.1. Schematic diagram of the slotted- electrode photovoltaic cell. (XBl 831-7974) _1_ -1_ 0 2 4 6 8 10 L4 /n *This work was supported by the Director, Off'se B of Energy Research, Office of Basic Energy Fig. 1.2. Maximum power density as a function of Sciences, Chemical Sciences Division of the U.S. Lftg/h for the slotted-electrode photovoltaic cell Department of Energy under Contract No. (t - 0.1 cm, h = 0.5 cm, and G = 1.0 cm). DE-AC03-76SF0009B. (XBL 831-7g?5) 182 * * * be reduced by a factor of ten thousand in a single pass through the reactor at flow rates as high as f *?n bed volumes per hour. The results are very Brief version of LBL-15494. encouraging, and the system appears attractive as a potential treatment method. 2. ELECTROCHEMICAL REMOVAL OF MUkCURY FROM CONTAMINATED BRINE SOLUTIONS1" * * *

Michael Matlosz and John Newman +Brief version of LBL-14708. Aqueous solutions contaminated with heavy-metal ions may present serious toxic health hazards. The use of high-surface-area electrochemical re 1982 PUBLICATIONS AND REPORTS actors, such as flow-through porous electrodes, shows promise for the effective treatment of LBL Reports these solutions. 1. Michael Matlosz and John Newman, "Use of a A flow-through porous electrode consists of a How-through Porous Electrode for Removal of support material (such as carbon), which is per Mercury from Contaminated Brine Solutions," pre meable and electrically conducting. A solution, sented at the Electrochemical Society Conference, contaminated with a heavy-metal ion (mercuric Montreal, quebec, Canada, May 10, 1982, LBL-14708. ion, in this case), flows through the bed, while a small electric current is drawn through the 2. Mark E. Orazem and John Newman, "Primary support material. The heavy-metal ions are Current Distribution and Resistance of a Slotted removed from the solution by electrodeposition Electrode Cell," LBL-15494. (electroplating) onto thy packing material. Invited Talks The experimental porous electrode used in this study is 3 in. in diameter and 6 in. in heiglit, 1. W. H, Smyrl, "Metal Displacement Reactions," and consists of a cylindrical bed of carbon flakes Electrochemical Society Conference, Montreal, and chips. Typically, mercury concentrations can Quebec, Canada, May 12, 1982. 183

g. Surface Cherniary—Application of Coordination Principfw* Earl L Muetterties, Investigator

The establishment of coordination principles initiation proceed'oceei s by the reaction sequence: -col for the chemisorption of hydrocarbons and their Re2

{HRh[P(0-i-C3H7)3]2)2: Preparation, Dynamic NMR and X-Ray Crystal Structure of Thermal desorption and isotopic labeling [^-CH2C6(CH3)5l-Rh[P(0-i-C3H7)332," Organo- studies have indicated that cycloheptatriene after metallics j., 188 (1982). chemisorption on ato^ically flat nickel and plat inum surfaces is dehydrogenated below ~90*C to 2. H. W. Choi and E. L. Muetterties, "The yield a C7H7 species. On Ni(lQO)., a substantial fraction of the implicated C7H7 surface species Synthesis and Chemistry of Binary Zerovalent is converted to benzene at temperatures of about Transition Metal Phosphite Complexes," J. Am. lOO'C. Tht isomeric molecule, norbornadiene, is Chem. Soc. H>4, 153 (1982). also partially converted to benzene at 225-250"C on Pt(lll) and Pt(100). Labeling studies estab 3. V. W. Day, I. Tavanaiepour, S. S. Abdel- lished that the carbon atom lost in the benzene Meguid, J. F. Kirner, L.-Y. Goh, and E. L. formation is the CH2 carbon atom. Cyclooctene Muetterties, "Modes of Phosphite Reactions with and cyclooctadienes were partially converted to Transition-Metal Complexes. Crystal Structures of (n5-C H5)Cr[P(0)(OCH )23(CO)2[P(OCH )3] and cyclooctatetraene on Pt(lll) at elevated temper 5 3 3 {[(CH H0y PMo[P(C0H3)3]|l(PF -),M Inorg. Chem. atures. 3 2 5 21, 657 (1982).

+ The postulated surface reaction of c-CnH2n_2m 4. R. M. wexler, M.-C. Tsai, C, M. Friend and M(surface) »M(surf )-c-C H + H{sur7)-H „2m n n n E. L. Muetterties, "Pyridine Coordination Chemis appears to have some general applications wiLuin try of Nickel and Platinum Surfaces," J. Am. Chem. the metal surface chemistry of cyclic olefins and Soc. 104, 2034 (1982). polyenes. The studies are being extended to other cycloalkenes and cyclopolyenes such as cyclobutene +5. M.-C. Tsai and E. L. Muetterties, "Platinum and cyclononene. Metal Surface Chemistry of Benzene and Toluene," J. Am. Chem. Soc. _104, 2534 (1982); LBL-13628. The absence of metal-metal bond scission in the course of RejfCOJip ligand substitution re +6. M.-C. Tsai, C. M. Friend, and E. L. actions has been definitively established.2 185 187 Muetterties, "Dehydrogenation on Nickel and Samples of pure Re2(CO)io and Re2(CO)io Platinum Surfaces. Conversion of Cyclohexane, were prepared front the isotopically pure metals. Cyclohexene and Cyclohexadiene to Benzene," 0. Ligand substitution reactions with CO and with Am. Chem. Soc. KI4, 2539 (1982); LBL-13629. triphenylphosphine were effected at 150*C with a mixture of 185Re2(CO)iO and lt;7Rfi2(CO)xo» and the products were analyzed by mass spectrometry. No 7. E.-B. Meier, R. R. B:irch, E. L. Muetterties cross labeled (l85Rel87Re) product was detected. and V. W. Day, "A Dinuclear Rhodium Complex with Ligand substitution in Re2(CO)io under thermal an Octahedral Rhodium(III) and a Square Planar Rhodium(I) Center," J. Am. Chem. Soc. 104, 2661 (1982).

8. E. L. Muetterties, J. R. Bleeke, Z.-Y. Yang, *This work was supported by the Director, and V. W. Day, "Complexity in the Reductive Office of Energy Research, Office of Basic Energy Reaction of CoClj in the Presence of Phosphites. Sciences, Chemical Sciences Division of the U.S. Isolation of Stable, Noninterconvertible

Department of Energy under Contract No. Co[P(0CH3)3]4 and Co2[P(0CH3)3]8 Molecules," J. DE-ACO3-76SF00098. Am. Chem. Soc. 104, 294C (1982). 184

+9. M.-C. Tsai, J. Stein, C. M. Friend* and E. L. Invited Talks Huetterties, "Chemistry of Cyclic Olefins and Polyenes on Nickel and Platinum Surfaces," 3. Am. 1. E. L. Muetterties, "Hydrocarhon Reactions at Chem. Soc. 1M, 3533 (1982); LFL-14860. Metal Centers," Centenary Lecture of the Royal Chemical Society, London, Hay 13, 1982. 10. Tv. R. Burch, E. L. Muette-ties, R. G. Teller, and J. M. Williams, "Selective Formation of Trans- 2. E, L. Muetterties, "Cluster Chemistry," Olefins by a Catalytic Hydrojenation of Alkynes Stanford Research Institute, June 1982. Mediated at Two Adjacent Me'.al Centers," J. Am. Chem. Soc. \0A, 4257 (1982). 3. E. L. Muetterties, "Metal Surface Chemistry," American Vacuum Society Meeting, IBM Research 11. E. L. Muetterties, "The Organometallic Laboratories, June 1982. Chemistry of Metal Surfaces," Proceedings of the Xth International Conference on Organometallic 4. E. L. Muetterties* "Cluster Chemistry," Chemistry, 9-14 August, 1981, Pure and Applied Stanford University, February 1982. Chemistry 54, 83 (198?). 5. E. L. Muetterties, Plenary Lecturer, Inter f12. M.-C. Tsai, C. M. Friend, and E. L. national Conference on Inorganic Stereochemistry, Muetterties, "Dehydrogenation of Cyclohexane, University of Reading, England, 1982. Cyclohexene and Cyclohexadienes to Benzene on Nickel and and Platinum Surfaces," J. Va. Sci. * * * Technol. _20, 533 (1982); LBL-13450. fThis work was supported by the Director, Office 13. E. L. Muetterties, "Metal Clusters," C&E News of Energy Research, Office of Basic Energy Sci 60, No. 35, 28 (1982). ences, Chemical Sciences Division of the U. S. Department of Energy under Contract No. Other Publications DE-AC03-76SF00098.

1. E. L. Muetterties, R. R. Burch, and A. M. All other publications were funded by the Stolzenberg, "Molecular Features of Metal Cluster National Science Foundation under grants Nos. Reactions," Ann. Rev. Phys. Chem. ^3, 89 (1982). CHE-79-03933 and CHE-6000038.

i 185

h. High-Energy OxkJer* and Dek>caliz«f-Electron SoNdt*

Neil Bartlett, Investigator

Introduction. This research group is concerned carbon in KelF, thus also indicating that the F with the electron oxidation of aromatic molecules in CXF is highly negative. These findings and and-other electron-delocalized materials. A major the apparent preservation cr the planarity of the interest is graphite intercalation.* The fac carbon atom sheets (remarked upon in the previous tors that are important in bringing about inter report) indicate that the F atoms in CXF may be calation are being assessed as are the changes in linked to the C atoms two at a time, one F atom the properties (particularly the electv"cal con above and one below the C atom in a carbon-atom ductivity) which accompany the intercalation. sheet. The bonding orbital in such a three-center Since bands of the carbon-atom layers serve as four-electron F-C-F bond has the symmetry appro the source (valence band} of electrons or sink priate for w bonding to its graphite environment. (conduction band) for electrons, and substantial Thus the remarkable constancy of the in-plane C-C electron-oxidation or reduction can occur without distance over the entire CXF composition range disruption of the graphite-sheet structure, graph {see Table 1.1) is accounted for. Also the occu ite intercalation compounds offer the prospect of pied nonbonding orbital has no carbor^-orbital com appreciable electrochemical oxidation (or reduc tion) without catastrophic structural change. ponent and thus should bestow high negative charge on the F ligands. This model accounts for all of the observed properties, but it remains to be es For a clear understanding of intercalation, tablished. (Attempts to obtain J-resolved 13C NMR and its scope, it is essential to know the nature spectra that are in progress may provide the proof.) of the guest species (especially their charge), their concentration and, if possible, their dis Another indicator of unusual bonding of fluo position with respect to the carbon atoms of the rine to carbon comes from the finding that the infinite graphite sheet galleries within which intercalation of graphite by fluorine in the they are contained. The mobility of the species presence of HF is reversible. The intercalation within the graphite galleries is also of interest. can be reversed chemically or electrochamically, Efforts are being made to determine how quickly when x in CXF exceeds 2.3. By using a large and reversibly electrochemical oxidation and re excess of graphite as the reducing agent, a duction of the graphite salts can be carried out. high-stage graphite hydrofluoride is obtained How far the graphite can be oxidized before struc but electrochemical reduction provides for com turally destructive and irreversible changes c cur plete conversion back to graphite: is also being investigated.

CXF + e~ > xC + F-

Material of composition CXF may also be syn ]. For recent review see LBL-13751. thesized electrochemically to x * 2.6 (below which

value of x the CX r" becomes highly resistive).

1. AN ELECTROCHEMICALLY REVERSIBLE INTERCALATION OF GRAPHITE BY FLUORINE IN THE PRESENCE OF HYDRO

GEN FLUORIDE* Table 1.1. Some Physic;*/ Properties of CKF.

Tom Mallouk and Neil Bartlett

a0 c0 p XPS spectra, of representative samples of the new graphite fluoride CXF (5 > x > ?) reported C/F ratio (A) (A) (-Q - cm) last year, have been obtained in collaborative studies with Dr, K. 0. Bomben ami Professor W. L. 5.22(5)a 2.456(3)a 5.22(2)* >8 x 10"3 Jolly. The spectra show that tha carbon, even in the fluorine rich material of composition C2/5F, 3.67 2.459 5.36 8 x 10~* is graphite-like. The F Is binding energies show, however, that the fluorine is more negatively 3.20 2.456 5.45 3 x 10° charged than in Teflon or carbon monofluoride. although less so than the fluorine in LiF. 13c 2.70 2.460 5.71 2 x 10l NMR studies, in collaboration with the Colorado State University NMR Regional Cent°r, also show 2.42 2.459 6.02 1 x 103 that much of trie carbon of CXF remains graphite like, and that the remaining carbon (presumably 2.15 2.468 6.22 1 x 107 that bound to F) is chemically shifted beyond 1.94 2.464 6.45 2 x 10?

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sci aNumerals in parentheses are estimated standard ences, Chemical Sciences Division of the U.S. deviations for the last place quoted. The e.s.d. Department of Energy under Contract No. for each set of numbers in a vertical column is DE-AC03-76SF00098. approximately constant. 186

Such syntheses have used lead difluorlde (which Since some ASF5 can be retrieved [although is a good F- ion conductor) as the source of F~ always accompanied by AsF3, formed according to and HF/NaF solution as electrolyte. Hence, the (1)3 from first stage compounds made from graphite

system CXF |HF-NaF|M, where M is a metal not and AsFij, it appears that the conversion according oxidized by K+ (e.g., Pb, Ag, Cu, Hg), affords to (1) is not complete in the first stage materi a secondary battery. Open circuit voltages of al. It is therefore probable that the electron

CXF against pb|PbF? have been determined (x in affinity of ASF5 [according to half reaction parentheses): (3.7), 2.03; (2.7), 2.20; (2.5), (1)] is close to threshold. Clearly the corre 2.38 volts. sponding electron affinity for the phosphorus analogue must lie below such a threshold. These electron affinities have been evaluated. The Thus, CXF p j.nises to exhibit novel F bond ing to carbon (with perhaps five coordinate car threshold electron affinity for graphite inter bon) and also is a highly reversible and powerful calation by species similar in size and charge to oxidizing electrode material. PFg" must be greater than 86 kcal mole"* and per haps close to the value of 121 V.cal mole"* observed for the AsFg~ case.

^Based on LBL-13815 and L8L-15173.

fBased on LBL-15495. 2. A THERMODYNAMIC THRESHOLD FOR THE INTERCALA 1. B. W. McQuillan, Ph. 0, thesis, University of + TION OF GRAPHITE BY HEXAFLUOROSPECIES MF6" California, Berkeley, 198T». 2. B. W. McQuillan and Neil Bartlett, "Graphite Guy L. Rosenthal and Neil Bartlett Chemistry," in Intercalation Chemistry, edited by M. Stanley Whittingham and Allan J. 3acobson, Previous work in these laboratories**? had Academic Press, New York, June 1982, p. 19-53. indicated that the intercalation of graphite 3. N. Bartlett, R. K. Baigioni, B. W. McQuillan, by hexafluorides required an oxidizing poten A. S. Robertson and A. C. Thompson, 0. C. S. tial greater than that afforded by ReFg but Chem. Comm., p. 200 (1978). less than that of liexafluorides such as OsFg, IrFs, and PtFg. The electron affinity thresh old appeared to be close to 120 kcal mole-1, but that this was a thermodynamic threshold 3. INTERCALATION OF GRAPHITE BY SILICON TETRA- and not a kinetic one was not determined. Stud FIU0R10E AND FLUORINE TO YIELD A SECOND-STAGE SALT ies of the hexafluoroarsenate and hexafluoro- C24S1F5t phosphate salts of graphite have now establishert such a thermodynamic threshold. G. L. Rosenthal, T. E. Malli'uk, and Neil Bartlett The finding-* that graphite intercalate by Assessment of the fluoride ion affinity of SiF4 arsenic pentafluoride is associated wiih electron- by Beauchamp and Murphyl places this affinity as oxidation of the graphite according to the half slightly inferior to that of BF3. Since the latter reaction: is intercalated readily by graphite in the pres ence of fluorine, it appeared probable on thermo + 3 AsF5 + 2e" * 2 AsF6- AsF3 (1) dynamic grounds that SiFjj. would be similarly in tercalated in the presence of elemental fluorine. and that graphite was not similarly intercalated Such intercalation does occur at ~40"C with 1:1 by phosphorus Dentafluoride, which is physically SIF4IF2 mixture (-50 atm) to yield a second-stage similar to ASF5, suggested that graphite inter compound [an = 2.46(1), cQ = 11.29(1) A] of calation by such fluorides depended primarily on composition C~24SiF5. This product interacts with the oxidizing potential of the fluoride. Indeed excess PF5, with quantitative displacement of SiF4, 2 earlier studies in these laboratories had es to yield a first-stage fluoijphosphate [a0 = tablished the synthesis of graphite hexafluoro- 2.46(1), c0 =* 7.65(1) A] according to the equa + tion: phosphates Cx PFg~ by exploiting the very favor able energy of formation of PF^~ via the reaction:

C24SiF5 + 2 PF5 » C24PF6-PF5 + SiF4 (1) + PF5(g) + 1/2 F2(g) e- » PF6-(g) . (2) This first-stage fluorophosphate falls to a sec In the present work second and higher stage c +pf: ond-stage salt [aD = 2.46(1), c0 = 10.87(1) x 6~ salts have been reduced to graph A] under vacuum: ite by phosphorus trifluoride:

PF + 3 PF + 2e C PF -PF i£Xc PF + PF (2) 3(g) 2 PF6"(g) * 5(q> ~ • W 24 6 5 24 6 S These reductions proceed spontaneously at 20°C and x-ray powder photographs of the reduced prod The second stage fluorophosphate can be prepared uct are indistinguishable in d_ spacings, and al directly, but it is harder to obtain a pure sec most as sharp as the photographs of the starting ond-stage material than via the Cp^SiFs salt. graphite. Clearly the phosphorus equivalent of c24SiF5» like C24PF6 tsee E(l- (2)J is reduced to reaction (1) does not occur because the free-ener graphite by PF3, at 20°C, thus indicating that the gy change for PFg- and PF3 formation is much less original C24SiF5 synthesis does not involve exten favorable than for arsenic species. sive C-F bond formation. 187

The ease of displacement of S1F4 by superior or M. Stanley Whittingham and Allan J. Jacobson, less volatile fluoroacids makes C24S1T5 a valuable Academic Press, New York, 1982, P. 19-53; reagent for the production of graphite salts, some of LBL-13751. which are not otherwise accessible. Thus, the flu- orophosphorane C6F5PF4 cannot be directly inter 2. Neil Bartlett, "Electron-Oxidation of Aromatic calated by graphite in the presence of fluorine be Molecules, Layer-Form Boron Nitride and Graphite," cause it is fluorinated by elemental fluorine to in Thg Chemical Industry, edited by D. H. Sharp yield PF5 and CgFs. When added to C24SiF5, only and T. F. West, Ellis Harwood Ltd., Chichester, S1F4 is observed as a volatile rnd the fluoro- England, 1982, p. 292-305; LBL-12475. phosphorane is intercalated: 3. Neil Bartlett, "Rado," in Encic.jpedia della

SiF5- + C6F5PF4 » C6F5PF5- + SIF4 Chimica, Vol. IX, 1982, p. 312-3H, USES Edizioni Scientifiche, Firenze, Italy. Thus, C24SiF5 acts as a mildly oxidizing fluoride source and should find wider application in graph ite salt synthesis. Invited Talks

* * * 1. Neil Bartlett, "Electron Oxidation of Aromatic Molecules and Other Electron Delocalized Systems," teased or, LBL-15457. Oalton Division, Annual Chemical Congress, Royal 1. M. K. Murphy and J. L. Beauchamp, J. Am. Society of Chemistry, University of Aston, Chem. Soc. 99, 4992 (1977). Birmingham, England, March 31, 1982.

2. Neil Bartlett, "Stabilizing High Oxidation 1982 PUBLICATIONS AND REPORTS States," National Main-Group Chemistry Workshop, Keystone, Colorado, June 1, 1982. LBL Reports 3. Neil Bartlett, "Heats of Formation of Fluoro- 1. G. L. Rosenthal, T. E. Mallouk, and Neil Am'ons and Their Relationship to Graphite Inter Bartlett, "Intercalation of Graphite by Silicon calation," 183rd American Chemical Society Na Tetrafluoride and Fluorine to Yield a Second-Stage tional Meeting, Kansas City, Missouri, September

Salt C24SiF5," LBL-15457. 12-17, 1982.

2. Thomas Mallouk and Neil Bartlett, "Reversible 4. Neil Bartlett, "Stabilizing High-Oxidation Intercalation of Graphite by Fluorine: A New Bi- State Cations," 10th International Symposium on fluoride, CJ2HF2, and Graphite Fluorides CXF Fluorine Chemistry, University of Bricish Co umb- (5 > X > 2)," LBL-13815. ia, Vancouver, Canada, August 1-6, 1S52.

Other Publications 5. Neil Bartlett, "Graphite Intercalation by Fluorides and Fluorine," Max-Planck-Institut fiir 1. B. U. McQuillan and Neil Bartlett, "Graphite FestkBrperforschung, Giessen, Germany, October Chemistry" in Intercalation Chemistry, edited by 29, 1982. 188

I. Transition Metal Catalyzed Conversion of CO, NO, H2, and Organic Molecules to Fuels and Petrocnemteate*

Robert G. Bergman, Investigator

Introduction. The focus of current work on Recent results have (a) shown that intermedi this project is the elucidation of the mechanisms ate 2 has astonishingly wide C-H insertion by which metals induce the formation and cleavage reactivity, (b) provided information about the of carbon-hydroger. (C-H) bonds. In one group of mechanism of the reaction, (c) uncovered a ther studies, a new set of C-H bond forming processes mal method for carrying out the C-H activation involving two metals has been found; some of this reaction, (d) provided information about the work was summarized last year. More recently, relative rates of reaction of 2 with different the remarkable discovery of an organometallic types of hydrocarbons, and (e) allowed development system in which the metal inserts into the C-H of a method for functionalization of the hydrido bonds of completely saturated hydrocarbons, lead alkyl complexes 3. ing directly to hydridometal alkyl complexes, has been made. Despite much investigation, this is The breadth of reactivity of this system has the first such system to be reported, and current been demonstrated by carrying out the irradiation efforts are directed at exploration of the de of 1 in a wide range of solvents. So far, every tailed chemical properties of this system and solvent investigated has proven to be reactive. elucidation of the factors which make it work. Not all of these have been studied in detail, but competition experiments with several have allowed measurement of the relative rates at which the in 1. ACTIVATION OF C-H BONDS IN SATURATED HYDROCAR termediate 2 reacts with different types of C-H BONS ON PHOTOLYSIS OF (ri5-C5Me5){PMe3)IrH?. RELA bonds. Relative to cyclohexane (1.0), these are: TIVE RATES OF REACTION OF THE INTERMEDIATE WITH benzene (4.0), cyclopropane (2.65), cyclopentane DIFFERENT TYPES OF C-H BONDS, AND FUNCTIONAL- (1.6), neopentane (1.14), cyclodecane (0.23), cy- IZATION OF THE METAL-BOUND ALKYL GROUPS1" clooctane (0.09). Intramolecular relative reac tivity studies have also been carried out; for Andrew H. Janowicz and Robert G. Bergman example, the aromatic hydrogens in p-xylene (1,4-dimethylbenzene) react 3.7 times faster than Irradiation of iridium dihydride 1 in hydrocar the methyl hydrogens. This type of experiment has bon solvents neopentane and cyclohexane gives! the provided evidence against a radical mechanism for corresponding hydridoalkyl complexes 3. These are the reaction, which should favor attack at the methyl group, generating the more stable benzylic apparently formed by photochemical extrusion of Hg, radical. This mechanistic conclusion is rein producing reactive iridium intermediate 2; this forced bi experiments using isotopically Tabeled complex then undergoes oxidative addition into the solvents, and crossover experiments which demon C-H bond in the hydrocarbon, leading to stable strate that the hydrogen and alkyT group found on products 3a and 3b (see Scheme 1).

+RH

[(C5Me5)(PMe3)lr] T~^ (C5Me5)(PMe3)lr( 110°

-RH 3a, R = C6H,, 3b, R = CI -> tBu

.CH2CH2CH2CH2CH3

11 • (CsMesKPMe^lrtHKCsH,,)- ^—(C5Me5)(PMe3)ir: 4,5,6,7 4 (4 isomers)

*This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division of the U. S. Department of Energy under Contract No. DE-AC03-76SF00098. 189

each molecule of product 3 were associated with one another in the starting hydrocarbon. A radi * * * cal mechanism seems especially unlikely in view TBrief version of LBL-14421 and LBL-15145. of the reactivity of the C-H bonds in cyclopro 1. A. H. Janowicz and R. G. Bergman, J. Am. Chem. pane, which have very high bond energy (106 Soc. 104, 352 (1982). kcal/mole).

The dihydric'e 1 is quite stable thermally. 2. WORK IN PROGRESS However, heating a given, hydridotlkyl complex 3 to 110" causes reductive elimination of hydrocar On the iridium system summarized above, re bon, regenerating 2 which is then able to insert search continues aimed at understanding the fac into the C-H bond of other hydrocarbons. In this tors which make the system uniquely reactive toward way, the hydridoalkyl complexes may be used as intermolecular attack on saturated hydrocarbons. starting materials for thermal C-H activation re Investigation of the reactions of intermediate 2 actions. This thermal reaction has also allowed with a wider range of organic substrates is being us to investigate the differences between kinetic explored, and special attention is being paid to and thermodynamic products formed in these reac those (e.g., methanol and certain dienes) which tions. For example, as shown in Scheme 1 irra seem to give unusual products. Analogs of 1 diation of 1 in n-pentane at 0* gives four which contain phosphine ligands other than PMe3 products (4-7), derived from insertion of 2 have been synthesized, and their hydrocarbon ac into each of the different types of C-H bonds in tivation reactions are being studied. Some of the hydrocarbon (two diastereomers are formed on these ligands have electronic properties very insertion into tfe C-H bonds at C-2). Heating different from those of PMe3 and PPh3- In this mixture to .10", where reversible elimina ethers longer alkyl chains, capable of both tion and C-H readdition occur, results in conver inter- and intramolecular reaction, are present. sion to the thermodynamic product, which is solely Finally, a successful method for preparing the the primary hydridoalkyl complex 4. Thus, quite corresponding rhodium dihydride (n^-CsMes)- selective activation of a primary C-H bond in a (PMe3)RhH2 has been developed. It, too, effects linear hydrocarbon can be achieved. C-H activation reactions of completely saturated hydrocarbons, although in this case the products are stable only at low temperatures. This system Functionalization of the alkyl group of com is now being explored in detail. plexes 3 has been carried out using the multi- step sequence illustrated in Scheme 2. Conver sion of 3 to the corresponding bromoalkyl com plexes 8 is effected smoothly using CHBr3. Treatment of this material with HgCl2 results in transfer of the alkyl group to mercury; halo- genation of the resulting alkylmercurial 9 1982 PUBLICATIONS AND REPORTS delivers the corresponding alkyl halide 10 in good yield. This sequence therefore provides an Refereed Journals overall method for stoichiometric conversion of a hydrocarbon into an alkyl halide, using a method 1. A, H. Janowicz and R. G. Bergman, "C-H Acti which avoids free radical intermediates. vation in Completely Saturated Hydrocarbons: Di rect Observation of M + R-H » H(R)(H)," J. Am. Chem. Soc. 104, 352 (1982); LBL-13402. Scheme 2 +2. K. H. Theopold, W. H. Hersh, and R. G. Berg man, "BinucTear Metallacycles: OrganometaTlic CHBr, Ring Systems Containing Two Metal Centers," Isr. / J. Chem. 22, 27 (1982). (C5Me5)(PMe3)K •(C5Me5){PMe3)l / 3 H 8 Br +3. K. H. Theopold and R. G. Bergman, "Carbon-to- Carbon Migration of the Dimetallic Group in Dinu- clear Cobalt Alkylidene Complexes," Organometal- lics 1., 219 (1982). ,Br HgCU /" £ *4. K. H. Theopold, P. N. Becker, and R. G. Berg 8 —^- -(C5Me5)(PMe3)lr' +RHgCI man, "Asymmetric Induction in Reactions EmDloying CI 9 Enolates Generated from Cyclic Organotransition- Metal Acyl Complexes," 0. Am. Chem. Soc. 104, 5250 (1982).

*5. K. H. Theopold and R.G. Bergman, "Synthesis, Crystal and Molecular Structure, and Chemistry of 9—'•R-Br+HgCIBr (g-Trimethylene)bis(n-cyclopentadienyl)bis-(p-car~ bonyl)dicobalt, a Five-Membered Dicobaltacycle," 10 Organometallics ^, 1571 (1982). 190

LBL Reports Metallac.ycles," Gordon Research Conference on Stereochemistry, Ptymoutfi State College—North, 1. A. H. Janawicz, Ph. 0. Thesis, "A Mechanistic Plymouth, New Hampshire, June 29, 1982. Study of the Formation and Cleavage of C-H Bonds: Hydrogenolysis of M-C Bonds/C-H Bond Activation 6. R. G. Bergman, lectures on: (a) Migratory of Saturated Hydrocarbons," L8L-14421. Insertion Reactions, (b) The Oxidative Addition Reaction, and (c) Metallacycles, University of 2. A. H. Janowicz and R. G. Bergman, "Activation Utah, Organometallic Chemistry Workshop, Salt of C-H Bonds in Saturated Hydrocarbons on Photol Lake City, Seotember 21-24, 1982. 5 ysis of (n -C5Me5)(PMe3)IrH2. Relative Rates of Reaction of the Intermediate with Different Types 7. R. G. Bergman, "Transformations of Organic of C-H Bonds, and Functionalization of the Metal- Compounds Induced by Transition Metal Complexes," Bound Alkyl Groups," LBL-15145. Department of Chemistry, Oberlin College, Oberlin, Ohio, November 8, 1982. fnvited Talks 8. R. G. Bergman, "The Use of Organotransition 1. R. G. Bergman, "Formation of New Bonds to Metal Complexes in the Formation of Carbon-Nitro Carbon Using Organotransition Metal Complexes," gen Bonds," Dyson Perrim Laboratory, University Department of Chemistry, University of North Car of Oxford, England, November 29, 1982. olina, January 14, 1982; Department of Chemistry, University of Arizona, Tucson, Arizona, March 15, 9. R. G. Bergman, "C-H Activation of Saturated 1982; Department of Chemistry, University of Wis- Hydrocarbons Using Soluble Iridium Complexes," ccr.sin at Madison, April 2, 1982; and Department Meeting of the Royal Society of Chemistry—Dalton of Chemistry, University of California, Riverside, Division, London, England, November 30, 1982 and October 13, 1932. Institut de Chemie des Substances Naturelles, Centre National de la Recherche Scientifique, 2. R. G. Bergman, "Homogeneous Intermolecular Gif-sur-Yvette, France, December 3, 1982. Oxidative Addition of Iridium to Single C-H Bonds in Completely Saturated Hydrocarbons," Shell De 10. R. G. Bergman, "Intermolecular Activation of velopment Company Westhollow Research Center, C-H Bonds in Saturated Hydrocarbons Using Soluble Houston, Texas, March 24, 1982; 65th Chemical In Iridium Completes," Table Ronde Roussel Uclaf, stitute of Canada Conference, Toronto, Canada, Direction des Relations Scientifiques, Paris, June 1, 1982; 28th Stanford University Industrial France, December 2-3, 1982. Affiliates Symposium on Homogeneous Catalysis, StanFord University, California, July 1, 1982, 11. R. G. Bergman, "Activation of C-H Bonds in and Microsymposium on Kinetics and Mechanism, 3rd Completely Saturated Hydrocarbons Using Soluble International Symposium on Homogeneous Catalysis, Iridium Complexes," Institut de Chimie, University Milan, Italy, September i, 1982. Louis Pasteur de Strasbourg, France, December 6, 1982 and Laboratoire de Chimie de Coordination 3. R. G. Bergman, "C-H Activation," Catalytica Organique, University de Rennes, France, December Associates Inc., Santa Clara, California, April 8, 1982. 19, 1982.

4. R. G. Bergman, general lectures on Reaction Mechanisms, A. C. S. Intensive Refresher Course * * * in Organic Chemistry, University of Wisconsin, ^Supported by the National Science Foundation Madison, Wisconsin, June 23-25, 1982. (Grant No. CHE79-Z6291).

5. R, G. Bergman, "Asymmetric Induction in Car 'Supported by the National Institutes of Health bon-Carbon Bond Forming Reactions Using Cobalt (Grant No. GM-25459). 191

5. Chemical Engineering Sciences

a. High-Pressure Phase Equilibria in Hydrocarbon-Water (Brine) Systems*

John M. Prausnitz, Investigator

Introduction. The need for new sources of in a constant-temperature air bath. After equi energy has produced interest in recovery of libration, small samples of each phase (less than natural gas from aquifers in Louisiana, Texas, 100 yl each) are removed from the 165-ml cell and the Gulf of Mexico Region. These aquifers under carefully controlled conditions to avoid contain large amounts of natural gas (mostly changes in composition. Samples of the vapor and methane) in contact with water or brine. It is liquid phases are taken at separate times to dis estimated that at least a 50-year supply of turb the equilibrated phases as little as possi natural gas is recoverable at current annual U.S. ble during sampling. The sample of the liquid consumption rates of natural gas.1 phase is flashed completely to form a vapor. The high-pressure, vapor-phase sample is expanded to Pressures in the aquifers may be as high as low pressure. The pressure on each sample after 150U bar. Temperatures may be as high as 270"C. these operations is in the range 10-40 psia. At present, it is not economic to mine these Subsequent to the expansion-flash step, the reservoirs but, in view of the large deposits, samples are analyzed using a gas chromatograph there is much incentive to make such mining equipped with a gas-sample valve. attractive. The purpose of this project is to obtain some of the fundamental physicochemical We have measured high-pressure solubilities of information needed to design such mining opera methane in water at 140 and 160*C and found the tions. For efficient recovery of natural gas data to agree with those of Sultanov et al.1 from aquifers, high-pressure, vapor-liquid equi Experimental work continues for the methane/water librium data are required. In addition, these system, toward extension to the methane/water/salt data are useful for estimating how much natural system. gas is present in the aquifers. Our goals are twofold: First, we seek to study experimental * * * high-pressure, vapor-liquid equilibria pertinent to natural-gas aquifers. Second, we want to represent the phase equilibria with a molecular- 1. R. G. Sultanov, V. G. Skripka, and A. Yu. thermodynamic model. Namiot, Gazov. Prom. U_y 6 (1972).

2. MODELING OF HIGH-PRESSURE PHASE EQUILIBRIA

1. R. A. Kerr, Science ^07, 1455 (1980). Eldon R. Larsen and John M. Prausnitz

For low-molecular-weight, nonpolar fluids 1. EXPERIMENTAL HIGH-PRESSURE VAPOR-LIQUID (e.g., light hydrocarbons), simple equations of EQUILIBRIUM state correlate vapor pressure and some volumetric properties reasonably well. Polar fluids (notably Jack Wong, Gabriele Di Giacomo, Eldon R. Larsen, water) cannot be treated so easily. For mixtures, Georg Roessling, and John M. Prausnit2 the equation of state must be written as a (non- obvious) function of composition. Experimental high-pressure, phase-equilibrium data for natural-gas/brine mixtures are scarce. We use a method that allows superposition of We have designed and built a high-pressure equi the residual thermodynamic properties of pure librium cell foropressures to 2000 bar and tem methane and of pure water. This method employs peratures to 400°C. The cell is fabricated of the theorem of corresponding states with molecu INC0NEL (a high-strength, corrosion- resistant, lar shape factors. These shape factors are con nickel-chromium alloy); all other wetted compo stants for simple fluids, but for polyatomic nents are cold-worked 316-stainless steel. At fluids, they may be functions of temperature and/ present, we are studying the methane/water sys or density. We apply reasonable mixing rules to tem. The methane/water mixture is stirred with a the superimposed properties to obtain residual chromium-plated, cylindrical, magnetically driven properties for the mixture. From these proper mixer. The cell and related tubing are enclosed ties, we calculate phase equilibria.

The shape factors for methane are constants. For water, one of the shape factors is constant, one varies with temperature, and one varies with temperature end density. Using reasonable mixing *This work was supported by the Director, Office rules, we are able to model well phase equilibria of Energy Research, Office of Basic Energy for the water/methane system to high pressures Sciences, Chemical Sciences Division of the U.S. and temperatures. This suggests that a useful, Department of Energy under Contract No. first basis is now available for calculating DE-AC03-76SF00098. phase equilibria for natural-gas aquifers. 192 1982 PUBLICATIONS AND REPORTS Invited Talks Refereed Journals 1. D. Dimitrelis, and J. H. Prausnitz, "Thermo dynamic Properties of Strongly Nonideal Fluid 1. W. B. Whiting and J. H. Prausnitz, "Equations Mixtures From an Extended Quasi-Chemical Theory," of State for Strongly Nonideal Fluid Mixtures: Annual Meeting of American Institute of Chemical Application of Local Compositions Toward Density- Engineering, Los Angeles, California, November Dependent Mixing Rules," Fluid Phase Equilibria 1982. 9, 119 (1982); LBL-14012 and LBL-14013). 2. D. Dimitrelis, R. J. Topliss, and J. M. \. G. M. Lobien and J. M. Prausnitz, "Infinite- Prausnitz, "High-Pressure Vapor-Liquid Equilibria Dilution Activity Coefficients From Differential in Ternary Systems Containing Two Miscible Liquids Ebulliometry," Ind. Eng. Chem. Fund. 21, 109 and One Supercritical Gas," Industrial Physical (1982). Chemistry Group Meeting of the Royal Society of Chemistry, Faraday Division, Cambridge, United *3. G. M. Lobien and J. H. Prausnitz, "Correlation Kingdom, September 1982. for the Ratio of Limiting Activity Coefficients for Binary Liquid Mixtures," Fluid Phase Equilib 3. E. R. Larsen, "Molecular Thermodynamics of ria 8, 149 (1982). High-Pressure Phase Equilibria for the Methane/ Water System," Department of Chemical Engineering 4. V. Brandani and J. M. Prausnitz, "Two-Fluid Colloquium, University of California, Berkeley, Theory and Thermodynamic Properties of Liquid California, June 1982. Mixtures: General Theory," Proc. Natl. Acad. Sci. (USA) 79(14), 4506 (1982). 4. E. R. Larsen, "High-Pressure Phase Equilibria for the Methane/Water System," Shell Research 5. V. Brandani and J. M. Prausnitz, "Two-Fluid Co., Houston, Texas, March 1982; Exxon Production Theory and Thermodynamic Properties of Liquid Research Co., Houston, Texas, March 1982; Union Mixtures: Application to Hard Sphere Mixtures," Carbide Corp., Charleston, West Virginia, March Proc. Natl. Acad. Sci. (USA) 79(16), 5103 (1982). 1982; and CONOCO, Ponca City, Oklahoma, June 1982. 6. V. Brandani and J. M. Prausnitz, "Two-Fluid 5. J. M. Prausnitz, "Molecular Thermodynamics Theory and Thermodynamic Properties of Liquid for Chemical Process Design," Chemical Engineering Mixtures: Application Simple Mixtures of Non- Department, Cornell University, Ithaca, New York, slectrolytes," Proc. Natl. Acad. Sci. (USA) December 1982; Chemical Engineering Department, 79(18), 5729 (1982). State University of New York, Buffalo, New York, April 1982 (Union Carbide Lecture); and Chemical *7. E. M. Pawlikowski, J. Newman, and J. M. Engineering Department, University of Texas, Prausnitz, "Phase Equilibria for Aqueous Solu Austin, Texas, April 1982 (van Winkle Lecture). tions of Ammonia and Carbon Dioxide," IEC Proc. Des. Oev. 21, 764 (1982). 6. J. M. Prausnitz, "Recent Developments in Phase Equilibria for Petroleum Process Applica 8. R. Rittman, H. Knapp, and J. M. Prausnitz, tions," Chemical Engineering Department, Shell "Enthalpy and Dew-Point Calculations for Aqueous Development Co., Houston, Texas, December 1982; Gas Mixtures Produced in Coal Gasification and and Chemical Engineering Department, Texaco Similar Processes," IEC Proc. Des. Dev. 21, 695 Research Co., Houston, Texas, December 1982. (1982). 7. J. M. Prausnitz, "The Generalized van der '9. E. C. Bishop, W. Popendorf, D. Hanson, and Waals Model for Dense Fluids and Fluid Mixtures," J. M. Prausnitz, "Predicting Relative Vapor Joint US and Chinese Meeting of American Insti Ratios for Organic Solvent Mixtures," Am. Ind. tute of Chemical Engineering, Beijing, People's Hyg. Assoc. J. 43(9), 656 (1982). Republic of China, September 1982. 8. S. I. Sandler and J. M. Prausnitz, "The Generalized van der Waals Theory," Annual Meeting Other Publications of American Institute of Chemical Engineering, Los Angeles, California, November 1982. 1. E. M. Pawlikowski, J. Newman, and J. M. Prausnitz, "Vapor-Liquid Equilibrium Calculations 9. G. T. Caneba, D. S. Soong, and J. M. for Aqueous Mixtures of Volatile, Weak Electro Prausnitz, "Diffusion and Sorption of Organic lytes and Other Gases for Coal Gasification Pro Volati les in SBS Block Copolymers and SBR Random cesses," Chem. Eng. Thermodynamics 1982, edited Copolymers," Annual Meeting of American Institute by Stephen A. Newman, Ann Arbor Science of Chemical Engineering, Los Angeles, California, Publishers. November 1982. 2, N. Knaup, P.. Doering, L. Oellrich, 10. J. M. Prausnitz, "Generalized van der Waals U. Ploecker, arm J. M. Prausnitz, "Vapor-Liquid Theory as a Basis for Phase-Equilibrium Calcula Equilibria for Mixtures of Low Boiling Substan tions in Chemical _.Sneering," American Society ces," DECHEMAJ^hejnist^^ Vol. VI, for Engineering Education, Santa Barbara, 1982. California, August 1982. 193

* * * §This work supported by the Humboldt Foundation. ^This work supported by a grant from the +This work supported by a grant from the National Operational Safety and Health Administration. Science Foundation. *This work supported by a grant from the National Science Foundation and a Hertz Fellowship. Nuclear Sciences

i 195

A. Low-Energy Nuclear Science

1. Heavy Element Chemistry

a. Actlnkfe Chemistry*

Norman M. Edttlstein, Richard A Andersen, Neil Bartlett, John G. Conway, Kenneth N. Raymond, Glenn T. Seaborg, Andrew Streitwieser, Jr., David H. Templeton, and Alan Zalkin, Investigators

Introduction. The central purpose of the pro- Specific Sequestering Agents for the Actinides ject in heavy element chemistry is to study lanthanide and actinide materials in order to provide the basic knowledge necessary for their safe and 1. LIPOPHILIC ENTEROBACTIN ANALOGUES. TERMINALLY economic use in present and future technology. N-ALKYLATED SPERMINE/SPERMIDINE CATECHOLCARBOXA- The work encompasses related applied problems in HIDES1* actinide chemistry. F.T. Welti, K. N. Raynond, and P. W. Durbin The program includes the prepp-'ation of new gaseous, liquid, and solid phases and studies of Linear polycatecholcarboxamide (LICAH) ligands their physical and chemical properties. Tech and their sulfonated (LICAMS) or carboxylated niques for characterization include x-ray dif (LICAHC) derivatives are very effective in remov fraction, optical and vibrational spectroscopy, ing Pu(IV) from mice, when administered intrave magnetic resonance, and magnetic susceptibility. nously or intraperitoneally. In order to increase Equilibrium and kinetic data for complex forma the lipophilicity of such compounds and thus alter tion are measured. From these complementary their distribution in vivo, a number of N-alky- studies, new insights into the structural and lated LICAM derivatives have been prepared. chemical principles of actinide compounds are obtained with which to design new synthetic The selective alkylation of the terminal schemes to produce new materials. nitrogen of spermine and spermidine have been accomplished by reaction of the amine with an Specific sequestering agents for the actinides appropriate aldehyde or ketone to form a Schiff continue to be developed and tested. Similari base. The latter was catalytically reduced with ties in the coordination chemistry, biological hydrogen. Reaction of the resulting alkylated transport, and in vivo distribution properties of amine with 2,3-dimethoxybenzoyl chloride and sub Fe(III) and Pu(lV), coupled with the observation sequent deprotection was carried out using previ that microbes produce specific and highly effec ously reported procedures (Fig. 1.1). tive sequestering agents for Fe(III), have led to the preparation and characterization of a number The effects of these bulky group-, on the ki of synthetic, biomimetic sequestering agents that netics and thermodynamics of complex formation, specifically complex Pu(IV) and other actinide(IV) in vivo organ distribution, and toxicity are cur ions. rently under investigation. A significant pre liminary result is that the N-alkylated LICAH The fundamental chemistry of organoactinide, derivations are primarily cleared via a hepatic and related organolanthanide compounds, their pathway, in contrast to the renal clearance of reactions, structures and bonding, are being more polar chelating agents. explored with the development of new materials, catalysts and reagents as the objective. De * * * tailed spectroscopic studies are continuing on these new materials, on actinide ions diluted in "fBrief version of LBL-12140; J. Org. Chera. 46, host single crystals, and on the free atoms and 5234 (1981). ™~ free ions of the actinide series in order to un derstand their elec nic structure and to com nhis work was partially supported by the National pare the properties of the f transition series Institutes of Health. with the more thoroughly studied d transition series.

This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sci ences, Chemical Sciences Division of the U. S. Department of Energy under Contract No. DE-AC03-76SF00098. 196

Potentiornetric titrations were used to deter mine the stabilities of Ca(II), Mg(II), Cu(II), I2(CH?]3NHICH2|4N> N II ft i% ParC. 3 Zn(II), Nf{II}, and Co(II) Kith several sulfonated R ICH lj (CH ] F 2 2 4 catechoylamide ligands: a bis(catechoylamide), U-e, 2a-c l,6-bis(Z,3-dihydroxy-5-sulfoben2oyl)-l,6-diazahex- ane (4-LICAHS); a tris(catechoylamide), 1,3,5- tris(2,3-dihydroxy-5-sulfobenzoyl)tris(aminomethyl) no. R R' benzene (HECflHS); a tetrakis(catechoylamide), 1,5, 10,14-tetrakis(2,3-dihydroxy-5-sulfobenzoyl)-l,5, Is (CH,),CH (CH.LCH 10,14-tetraazatetradecane (3,4,3-LICAMS). Struc lb CH,(CH,), CH,(CH,)t tural formulas for these ligands are shown in Fig lc C.H.CH, C.H.CH, ure 2.1.

Id C,H„ C.H„ For all ligands studied the titrations le CH,(CH,), CH,(CH,), 2« (CH,|,CH Zn(II) >Ni{II), Co(II) :• 2c C.H„ (CH,),NHC.H„ Hg(II) > Catll). These poly(catechoylamide) li gands possess great selectivity for ions of high charge to ionic radius ratios such as Fe(lII) and Pu(IV); their selectivity is similar to that shown by desferoxamine B, the current chelating agent ('or ion overload, and is greater than that demonstrated by DTPA, the chelating agent most p} ja often used for plutciium and other heavy-metal ion decorporation.

'''Brief version of LBL-14680; Inorg. Chem. 21, 3437 (1982). *This work was partially supported by the National 3|.,R = R' MCHjj.CH Institutes of Health. 3b, R •= R' = CH.ICH,), 3c, R = ft - C.H.CH,

3d, R = R'= CtH1L

3e, R = R' = CH,(CH3)T

4a, R = (CH1)1CH;R' - (CH,),N-CO- ' £-~HB 0 (a) 3 (or 4) equiv of DMBCI followed by 6 (or 8) equiv b of NEtj/THF. Excess BBr,/CUl« or CH,Cla followed by hydrolysis. Fig. 1.1. Preparation of N-alkylated spermine/ spermidine catecholcarboxamides. (XBL 831-7601)

2. FERRIC ION SEQUESTERING AGENTS. SELECTIVITY OF SULFONATED POLY(CATECHOYLAHIDES) FOR FERRIC

lON+t OH / Nc

3. GALLIUM AND INDIUM IMAGING AGENTS"*"* 4. SYNTHESIS AND STRUCTURAL CHEMISTRY OF TETRAKIS(THI0HYDROXAMATO)HAFNIUM(IV) IN S. M. Moerlein,§ M. J. Welch,§ V. L. Pecoraro, G. Hf(CH3C6H4{S)N(O)CH3)4-C2H50Ht* B. Wong, and K. N. Raymond K. Abu-Oari and K. N. Raymond 67Ga and Ulln have been used extensively as tumor imaging agents. Because these are group Determination of the coordination geometry of I118 elements with charges and coordination chem the unconstrained tetrafcis(bideitate)metalate(IV) istry similar to Fe(III), the catecholamide se complexes is a fundamental component in the de questering agents developed for that ion [and sign of an octadentate chelating agent that in Pu(IV)] h.;ve also been investigated as Ga- and corporates four such functionalities to form an In-binding radiopharmaceuticals. optimum metal coordination environment.

The solution equilibria for the reactions of W/ii'le we have prepared thiohydroxamate com Ga(III) and In(IIX) with the hexadentate ligands plexes of Th(lv), no crystals suitable for struc N,N',N"-tris(2,3-dihydroxy-5-sulfanatobenzyol)- ture analysis have been obtained. Instead, we l,3,5-tris(aminomethyl)benzene (MECAMS) and report the synthesis and structural characteriza N,N',N"-tris-(2,3-dihydroxy-5-sulfonatobenzoyl)- tion of the hafnium complex, the title compound. 1,5,10-triazadecane (3,4-LICAMS), and the bidentate catechol N,N-dimethyl-2,3-dihydroxy-5- The structure of the compound tetrakis- sulfonatobenzamide (DMBS) have been determined by (N-nethyl-p-thiotolylhydroxamato)hafnium(IV) dis spectrophotometry and potentiometric titrations. plays a bicapped trigonal prismatic coordination The effect of 3,4-LICAM-C (see Fig. 3.1) on the polyhedron, a polyhedron not observed for the biodistribution and clearance of "Ga was de catecholato and hydroxamato complexes studied to termined in Sprague-Dawley rats. date (see Fig. 4.1),

Both Ga(III) and In(III) are coordinated by three catechol ate groups at high pH and have formation constants of the order $HQ = +Brief version of LBL-13173; Inorg. Chem. 21, 1()38M-1. AS the acidity of the medium is 1676 (1982). — increased, the metal complexes of the hexadentate *This work was partially supported by the National sequestering agents undergo protonation reactions. Institutes of Health. In contrast, protonation of the M^^DMBSJs complexes results in dissociation of a catechol moiety to form MIII(DMBS)2- LICAM-C complexed °'Ga in vivo and hastened the renal clearance of the nuclide. The gallium concentration was decreased in all organs, with exception of the liver and spleen, where we suggest that hydroxide precipitates interfere with gallium sequestration by 3,4-LICAM-C. The gallium in abscess tissue was only slightly affected, giving rise to an increase in the °'Ga abscess-to-soft-tissue concentration ratio when 3,4-LICAM-C is adminis tered. Dosimetry calculations show that the siderophore decreases the radiation burden from 67Ga citrate.

+Brief version of Nucl. Med. 23, 501 (1982), and inorg. Chem. 21, 2029 (1982). *This work was partially supported by the National Institutes of Health. §The Edward Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110.

H CH^CHJCHJ^ CHtCH,CH,CHr SN N I I CO CO <§C <§C <§C Fig. 4.1. Perspective view and atom numbering Fig. 3.1. Chemical structure of 3,4-LICAM-C. scheme for tetrakis(N-methyl-p-thiotolylhydrox- (XBL 831-7602) amato)hafnium(lV). {XBL 799-11358) 198 Synthetic and Structure Studies of Actinides and Other Compounds

I. 0RGAN0URAN1UM COMPLEXES OF PYRAZOLE AND PYRAZOLATE. SYNTHESIS AND X-RAY STRUCTURES OF

U(C5Me5)2Cl2 (C3H4N2}, U(C5He5)2Cl(C3HiiN2). AND

U(C5Me5)IC3H3H2y2* C. W. Eigenbrot, Jr. and K. N. Raymond

As part of our effort to create, examine and explain structural and magnetic probes of the bonding in organolanthanide and actinide com pounds, we have sought the synthesis and magnetic characterization of an appropriate dimeric urani um complex. Our recent report of the synthesis and structure of UCp3(pz-) (pz- = pyrazolate) re vealed that our attempt to form a diroer (based on a precedent in titanium chemistry, [TiCp2(pz")2l) resulted instead in the formation of a monomeric species, allowing us to characterize a new mode of pyrazolate bonding. To investigate what role, if any, steric factors played in the formation of the monomeric compound and to learn mr/re about the pyrazolate ion as a ligand, we have adjusted the size and number of the CpfCsHs) ligands. Ws anticipated that a reduction in the total steric bulk of the other ligands might lead to the for mation of one or more dimeric species. Fig. 1.1. ORTEP drawing of the molecular unit The compound UCp2"Cl2 (Cp" = C^Mes) has proven of: al UCp?Cl2(pz); b) UCpjiCKpz-); and to be a useful starting material for other studies c) UCp2(pz-) . (XBL 831-7603) but does not produce dimers. Instead, the com 2 pounds U(C5Me5)2n(pzw) and UfCsMesJjipz-^ are formed by the reaction between UfCsMesJgC^ and stoichiometric amounts of Na(pz~). In the course 2. SYNTHESIS AND CRYSTAL STRUCTURES OF THE of this study, an adduct of neutral pyrazole, J TETRAKIS(METHYL-TSIHYDROBORATO) COMPOUNDS OF U(C^t le^)2^2(pz) (pz = pyrazole) was also char ZIRCONIUM(IV). THORIUM (IV), URANIUK(IV) AND acterized (Fig. 1.1). NEPTUNlUMflVF

The *H NMR, spectrum of UCpg"Cl2(pz) reveals R. Shinomoto, E. Gamp, U. M. Edelstein, 0. H. a fluxionality of the pyrazole ligand. The mag Templeton, and A. Zalkin netic behavior of both UCp^'Cljtpz) and UCp2"{pz-) is as one expects for U^+ ions. However, Actinide(IV) borohydrides are of considerable UCp2"(P2~)2 does not exhibit simil?r magnetic be interest because of their high volatilities which havior. Instead of decreasing witn increasing could prove useful for the separation of various temperature from an initial high value as the elements or for the separation of isotopes of the others, the susceptibility of UCp2"(pz~)2 has its same element. These compounds exhibit two minimum at low temperature and increases as the structural types. The first type, M(BH^)^ where temperature increases, until it becomes relatively M = Th, Pa, U, is a polymeric solid at room tem invariant with temperature. The crystal struc perature with markedly different volatilities for tures are illustrated in Fig. 1.1. various H, i.e., (U(BH4.)4 readily sublimes un der vacuum at 25*C vs -150*C for ThfBH^. The •*• * * second type of compound, where H = Np, Pu, is a volatile, chemically unstable liquid at room tem +BrieT version of LBL-13073; Inorg. Chem. 21, perature, aid a monomeric solid at ~10*C. In the 2653 (1983). second type the local symmetry about the metal 199

ion is tetrahedral and is like that found in +he structures consist of a body-centered packing of Zr and Hf borohydrides; however, the Np and Pu molecules. The coordination in these two com compounds crystallize in a different space group pounds is similar to that found in their boro 1 than the Zr and Hf compounds. Schlesinger, hydrides. The Zr-B distances in Zr{BH3CH3)4 and et al. have reported the synthesis and isolation Zr(BH4)4 are 2.335(3) and 2.34(3) A, respec of two methyl derivatives of uranium boronydride, tively; the Np-B distances in Np(BH3CH3)4 and the mono and tetra(methylborohydride) derivatives, Np(BH4)4 are 2.487(6) and 2.46(3) A, respectively. The Th and U complexes are very near to being U(BH4)3(BH3CH3) and U(BH3CH3)4-2 The mono(methyl borohydride) derivative and the tetra(methylboro- crystallographically isomorphous. The uranium hydride} derivative were expected to be monomeric compound is in a monoclinic space group, but in and of interest for spectroscopic and magnetic ths Th compound the b axis is inclined to the a__c measurements. We have prepared and investigated plane by about 2*, wftieh results in a triclinic space group. Whereas in the uranium compound the the properties of some methylated borohydrides unit cell contains two crystallographically dif and report in this article the synthesis and ferent but chemically identical molecules; the crystal structure of M(BH CH )4, H * Zr, Th, U, 3 3 thorium compound contains four. Within these and Np. structures the M-B bond lengths deviate less than 2a (for U) and 3o (for Th} from their respective The following synthesis gave satisfactory average, and the B-M-B angles in both structures yields. are all within 3o of being tetrahedral. chlorobenzene MC1 + 4LiBH CH > The(BH3(^3)4 sublimes easily under vacuum at 4 3 3 ~40"C which makes it the most volatile compound The reaction described above was also carried out of thorium known to date. in ether and THF. These solvents were satisfac tory for Zr(BH3CH3)4; but for U(BH3CH3)4 and Th{BH CH3)4, adducts with the solvent were formed. •''Brief version of LBL-15090. 3 1. R. H. Banks, N. M. Edelsteir,, B. Spencer, 0. Pure U(BH3CH3)4 prepared in ether could be sub limed from its adduct, but Th(BH3CH3)4 could not H. Templeton, and A. Zalkin, J. Am. Chem. Soc, be sublimed adduct-free. Use of chlorobenzene as 102, 620 (1980). TT H. I. Schlesinger, H. C. Brown, L. Horvitz, a solvent eliminated this problem. Np(BH3CH3)4 was prepared only in chlorobenzene. A. C. Bond, L. D. Tuck, and A. 0. Walker, J. Am. Chem. Soc., ]S, 222 (1953).

Zr(BH3CH3)4, NpfBh^O^, Th(BH3CH3)4, and

U(BH3CH3)4 are monomolecular in the crystalline state. The metal atom is tetrahedrally coordina 3. TERTIARY PHOSPHINE COMPLEXES OF THE f-BLOCK ted to the four methylborohydride groups of the METALS; PREPARATION OF PENTAMETHYLCYCLOPENTADIENYL- molecule. Twelve hydrogen atoms from the BH3 TERTIARY PHOSPHINE COMPLEXES OF YTTERBIUM (II AND entities are in close contact to the metal atom, III) AND EUROPIUM (II). THE CRYSTAL see Fig. 2.1. The Zr(BH:Cn3)4 and Np(BH3CH3)4 STRUCTURE OF Yb(Me5C5)2Cl(Me2PCH2PMe2)'t'

T. D. Tilley, R. A. Andersen, and A. Zalkin

As a continuation of our synthetic studies on the phosphine complexes of the f-block metals, we have studied the reaction of bidentate phosphines with the divalent metallocenes, MfMesCs^OEtg) where M is Eu or Yb. These studies were under taken with the view toward studying Lewis acid- base equilibria in these f-metal systems to pro vide a sound experimental i^asis for understand ing the bonding. This is ov considerable interest since tertiary phosphines were previously thought to be unable to form bonds to the f-elements.

The metallocenes M(Me5C5)2(0Et2) react with Me2PCH2CHoPMe2 to give hydrocarbon insoluble

H{Me5C5)2?Me2PCH2CH2PMe2)» M = Eu or Yb. These complexes are sparingly soluble in EtgO, but dissolve in tetrahydrofuran (THF) with displace ment of the phosphine giving M(Me5Cs)2(thf). The insoluble nature of the phosphine complexes sug gests that they are polymeric, the phosphine acting as a bidentate, bridging ligand rather than as chelating liyand. Consistent with this hypothesis, reaction of M(Ke5C5)2(0Et2) with Me2PCH2PMe2 gives the hydrocarbon soluble com

plexes M(Me5C5)2(Me2PCH2PMe2). The Yb complex may be oxidized by YbCl3 giving the trivalent

complex, Yb(Me5C5)2CliHe2PCH2PMe2)- The crystal Fig, 2.1. ORTEP drawing of Zr(BH3CH3)4. structure (Fig. 3.1) shows that the phosphine is (XBL 812-8217) 200

4. PKLPARATION AM) CRYSTAL STRUCTURE OF BIS- [BIS(PENTAHETHyLCyCLOPENTADIENyL>yTTERBRlUHtlII)]UN DECACARBONYLFERRATE, [{MesCsbYbMFejtCOhiJ: A COMPOUND WITH FOUR ISOCASBONYL (Fe-CO-Yb) INTERACTIONS*

T. D. Tilley and R. A. Andersen

We have continued our synthetic and bonding studies on Yb(Me5C5)2(0Et2) to act as a single electron-transfer reagent toward organometallic compounds. These studies are aimed at activating coordinated carbon monoxide by coordination of the Lewis acid, Yb(Me5C5)2, to the oxygen atom of carbon monoxide followed by electron transfer to the lowest unoccupied molecular orbital of carbon Fig. 3.1. ORTEP view down the centroids of the Cp monoxide. These two processes will lengthen and rings. (X6L 823-8224) weaken the carbon-oxygen triple bond and activate the ligand for further reaction with reagents, such as, hydrogen. These studies will provide data that might be useful for modeling the acting as a monodentate ligand, with Yb-P, Yb-Cl, heteronuclear activation of carbon monoxide. and Yb-C (ave.) bond distances of 2.94, 2.53, and 2.65 * 0.03 A, respectively. The cluster compound, Fe3(CO)i2, reacts with YbfMesCsMOEtp) to give the paramagnetic species •

It is of interest to note that Me2PCH2PHe2 is (n = 3.91 B.K. per Yb (III)), [yb(He5C5)2]2- displaced by diethyl ether in the divalent com [Fe3{C0)ij] which has CO stretching frequencies plexes showing that the coordinative affinity of In the infrared that are significantly lower in the divalent lanthanides toward phosphine is energy than found in the parent Fe3(C0)i2- Tnis rather poor relative to diethyl ether. This is fact suggests that coordination and electron in contrast to the observations in tetravalent transfer weakens the carbon-oxygen bond in the uranium in which the phosphines are not displaced complex. The crystal structure of the complex by oxygen or nitrogen donors. (Fig. 4.1) shows that it contains four bridging Yb-OC-Fe groups. The averaged Yb-C and Yb-0 dis tances are 2.57(1) and 2.243(3) A, respectively. The carbon-oxygen bond lengths in the Yb-OC-Fe unit are lengthened by 0.05 A relative to tBrief version of LBL-14367. ca.

cm -- ci2o

CIDl —Clio

Fig. 4.1. An ORTEP drawing of [Me6C5)2Yb]2[Fe3(C0)7(g-C0)4]. (XBL 815-9793) 201

normal bridging carbtfn-oxygen bond lengths, as the x-ray study. The hydrogen atoms are point expected on th* basis of the infrared data. ing away from the ytterbium atom, precluding any substantial Yb..,H interaction. The close Yb...C * * * approach could be because of a direct Yb...C in teraction, an unprecedented event, or because of +Brief version of LBL-13612. an interaction of the ytterbium atom with the electron pair in the C-H bond. In order to de scribe the bonding in a more precise fashion, a 5. TERTIARY PH0SPH1NE COMPLEXES OF THE f-BLOCK neutron diffraction study is planned so that the

METALS: CRYSTAL STRUCTURE OF Yb[N(SiMe3)2]2 hydrogen atoms may be located with high accuracy. [MejPCHoCHjPMe?]: EVIDENCE FOR A YTTERBIUM-Y- Nevertheless, the C-H bond activation observed is CARBON INTERACTIONt a useful model for the intramolecular activation of C-H bonds. T. D. Tilley, R. A. Andersen, and A. Zalkin .* * * We have extended the study of phosphine coordination complexes to the divalent silylamide +Brief version of LBL-14025. complexes, MLWSiMeo^]?, where M is Eu or Yb, in order to probe the effect of the nature of the anionic ligand relative to their ability to change the electron density on the metal atom. Since the 6. STEREOCHEMISTRY OF BIS(CARBOXYLATO)BIS MesCs ligands are more electron-donating relative (CHLORO)BIS(TERTIARY PHOSPHINEJ DIMOLYBDENUM to silylamide ligands, the former should afford COMPLEXES; CRYSTAL AND MOLECULAR STRUCTURE OF TWO more election rich compounds. Thus, silylamide ISOMERS Or (Me3CC02) Cl (PEt3)2MO2+ compounds should form thermodynamically stronger 2 2 bonds to phosphine donor ligands. John D. Arenivar, Vera V. Mainz, Helena Ruben, Richard A. Andersen, and Allan Zalkin The phosphine, Me2PCH2CH2PMe2, reacts with NaM[N(SiMe3)?]3 where K is Eu or Yb, or Compounds of the type MO2X2(PR3>2(02CR)2 Yb[N(SiMe3)2]2(0Et2)2 to give provide a potentially rich area for investigating

YbiN(SiMe3)2]2-(Me2PCH2CH2PMe2) or stereochemical phenomena in these quadruply Eu[N(SiMe3)2]2(Me2PCH2CH2PMe?)i.5. The coordina bonded, binuclear molecules since a variety of ted phosphine cannot be displaced by diethyl isomers are possible. Tetrachlorotetra(tri- ether, but the phosphine can be displaced by ethylphosphine)dimolybdenum reacts with two molar the stronger base, tetrahydrofuran. The crys equivalents of pivalic acid, Me3CC02H, to give tal structure (Fig 5.1) of the ytterbium com air-stable dichlorobis(triethylphosphine)- plex fhows that the Yb-P and Yb-B distances are bis(pivalato)dimolybdenum (A). In contrast, 3.012(4) and 2.331(13) A, respectively. More reaction of tetra(pivalato)dimolybdenum with significantly, a -y-carbon atom of the Me3Si triroethyl chlorosilane and triethylphosphine groups on each (Me3Si)2N-ligand is closer to the gives an air-stable compound (B) of the same ytterbium atom (3.04 A) than the sum of the van empirical formula as (A) but it is a different der Waals distance of Yb (II) and a methyl group geometrical isomer (Fig. 6.1). The crystal (3.7 A). As a consequence of this interaction, structures of both isomers have been determined the three hydrogen atoms on the y-carbon atom by conventional x-ray diffraction methods. The are locked in position and they were located in isolation of two isomers, beginning from differ ent starting materials, has not been observed in quadruply bonded molybdenum systems.

An interesting feature of isomer A is that the two oxygen atoms of each of the carboxylate groups are trans to two different ligands. This type of stereochemistry allows a comparison of the molyb denum-oxygen bond lengths as a function of the

CMe, CMe3

IP? MvtosssMo s o

CI PEt3 CMe3

(b) (a) Fig. 5.1. An ORTEP diagram of Fig. 6.1. Structural formulas for isomers A and B.

Yb[N(SiMe3)2]2 (dmpu). (XBL 8110-7070) (XBL 831-7557) trans-ligands within the same molecule. The av ture parameters for sodium praseodymium ethylene- erage molybdenum-oxygen bond distance trans to diaminetet**aacetate octahydrate and the isomor- chloride is'0.07 A (8c) shorter than the average phous samarium and gadolinium sal'.t. These salts molybdenum-oxygen bond trans to phosphine. This and several others crystallize according to the difference indicates that phosphine lies higher orthorhombic space group R!d2.3 This samarium than chloride in a trans-influence series in salt was used by Koetzle and Hamilton^ to meas Mo(IlI) chemistry. A structural comparison be ure anomalous neutron scattering. We repeated tween the two isomers is revealing since isomer A the determination of Sm using x-rays so that the has chloride ligands trans to a csirboxylate group synchrotron experiments could be analyzed with whereas isomer B has chloride ligi-.nds trans to atomic form factors identical {apart from anom triethylphosphine. The average molybdenum- alous scattering terms) with those used in the chloride bond length in isomer A is 0.02 A (flo) structure determination. Crystals that we have shorter than ths average molybdenum-chloride dis tested of the dysprosium compound, and also the tance in isomer B. This suggests that phosphine holmium one, are monoclinic, but with a struc lies higher on a trans-influence series than a ture very nearly the same as the orthorhombic carboxylate group. Combining this result with one. The rare earth oxide was dissolved in HC1 the one developed above, two inequalities may and mixed with a hot solution of the edta salt

be written: Et3P > Ke^CCOz and Et3p > CI. In a and crystals were grown by slow cooling or slow similar fashion, comparison of molybdenum-oxy evaporation. The x-ray diffraction data for the gen bond lengths between the two isomers yields three compounds were measured using MoKa x-rays. the inequality Me3CC02 > CI. Thus a trans- Crystal data and other details are listed in series, based upon bond length changes in the two Table 7.1. isomers, may be written Et3p > Me3C02 > CI. The trial structures for refinement were de rived directly or indirectly from Koetzle's5 coordinates for the Sm salt, but modified by var •tfirief version of LBL-13381. ious transformations of setting. With R value in the range 0.024 to 0.037 this work achieved its primary objectives of obtaining parameters which 7. ANOMALOUS SCATTERING BV PRASEODYMIUM, SAMARIUM fit x-ray diffraction intensities accurately AND GADOLINIUM AND STRUCTURES OF ETHYLENEDIA- enough to be used to analyze our synchrotron ra MINETETRAACETATE SALTS1" diation experiments cited above. A second result is the experimental values of f" for these three Lieselotte K. Templeton, David H. Templeton, r&re earth elements for MoKa radiation (Table Allan Zalkin, and Helena W. Ruben 7*1). Like our earlier results for Cs (Ref. 6) and Co and CI (Ref. 7) the agreement is excellent To measure anomalous scattering of x-rays by with the values calculated by Cromer and Liber- rare earth elements in experiments with synchro man^ for this wavelength remote from the ab tron radiation,1»2 we needed the crystal struc sorption edges. This is in contrast to huge

Table 7.1. Crystal and Diffraction Data, NaLn(edta)-8H20.

Ln Pr Sm Gd

a(A) 29.589(3) 19.503(11) 19.409(3)

b(R) 35.763(5) 35.596(17) 35.477(4)

c(S) 12.121(2) 12.119(5) 22.119(1)

U(A3) 8491.5 8413.4 8344.8

Dx(Mg m-3) 1.865 1.913 1.950

M, MoKa (mm-1) 2.38 2.90 3.29 unique reflections, F2 > o 3449 3368 3386

R = S ji |/E|F0 | 0.037 0.030 0.024

f'', exper. 2.67(11) 3.64(10) 3.91(9)

f'', calc. 2.82^ 3.442b 3.904°

aCromer and Liberman (1981). "Cromer and Liberman (1970). 203

differences observed in the immediate regions of 8. DIPOTASSIUMO BIS-([8]ANNULENE)YTTERBIUM(II) absorption edges. The crystal structure itself, AND BIS-([8]ANNULE»E)-CALCIUMt which has already been described by earlier authors cited above, needs little comment here. S. A. Kinsley and A. Streitwieser, Jr. The principal differences among these isomorphous crystals are the results of the different sizes The nature of the carbon-metal bonding in of the lanthanide ions. Corresponding distances organolanthanide compounds remains a matter of for our three structures tend downward consis continuing interest, lanthanides generally have tently with increasing atomic number, with an a stable +3 oxidation state, but several (e.g., average decrease of 0.061 A from Pr to Gd; the europium and ytterbium) also form divalent com ionic radii calculated from oxide and chloride pounds. The comparison of such compounds with structures9 decrease 0.075 A in th« same in those of the alkaline earth elements (e.g., cal terval. There is nothing novel obout the bond cium) is of especial interest because of the high structure of the 3dta moiety, but the redundancy ionic character of these systems. of these three determinations permits averaging of from 3 to 12 independent measurements to get accurate average values for each chemical type Many di-[8Jannulene compounds are known for +3 of bond distance and angle. These averages are lanthanides, but only a single such compound has shown in Fig. 7.1. been reported for the +2 state.1 We have now prepared and compared K2[VD(C8H8)2] and

Both compounds have identical IR s-jectra and •fBrief version of LBL-13866. similar x-ray power patterns. The infrared spec 1. L. K. Templeton, D. H. Templeton, and R. K tra strongly suggest a sandwich structure. Con Phizackerley, J. Am. Chem. Soc. WZ 1185 (1980). sequently, both compounds probably have identical 2. L. K. Templeton, 0. H. Templeton, R. P. crystal structures and bond character. These re Phizackerley, and K. 0. Hodgson, Acta. Cryst. sults further emphasize the lack of importance of A38, 74 (1982); T. Ueki, A. Zalkin, and D. H. the 4f orbitals in ytterbium(II) chemistry, e.g., Templeton, Act Cryst. 20, 436 (1966). the ring-metal interaction in these compounds is 3. J. L. Hoard, B. Lee, and M. D. Lind, J. Am. undoubtedly wholly ionic. Chem. Soc. 87, 1612 (1965). 1. T. F. Koetzle and W. C. Hamilton, Anomalous Scattering, edited by S. Ramaseshan and S. C. Abrahams, Munksgaard, Copenhagen, (1975), p. 498. TBrief version of LBL-15018. 5. T. F. Koetzle, private communication (1978). 1. A. Greco, S. Cesca, and G. Bertolini, J. 6. L. K. Templeton and D. H. Templeton, Acta Organometal. Chem. 113, 321 (1976). Cryst. A34, 368 (1978). 7. D. H. Templeton, A. Zalkin, H. W. Ruben, and L. K. Templeton, Acta Cryst. B35_, 1608 (1979). Physical and Spectroscopic Properties 8. D. T. Cromer and D. Liberman, 3. Chem. Pnys. 53, 1891 (1970); D. T. Cromer and D. Liberaan, 3cta Cryst. A37, 267 (1981). 1. OPTICAL SPECTROSCOPY AND ELECTRON PARAMAGNETIC 1 D. H. fempleton and C. H. Dauben, J. Am. Chem. RESONANCE OF Pa4+ IN ThBra AND ThCl4 CRYSTALS ' Soc. 76, 5237 (1954). J. C. Krupa, S. Hubert, M. Foyentin, E. Gamp, and N. Edelstein

Thorium tetrabromide and thorium tetrachloride are new host lattices for spectroscopic studies of tetravalent actinide ions, and' in some cases trivalent lanthanide ions. At room temperature 19 both crystals have a Dt^ tetrago.ial structure isostructural with UCI4. In this structure, the Th4+ ions are at a site of D2d symmetry and other tetravalent actinide ions can substitute into this site. Single crystal neutron diffraction experiments on ThBr4 revealed that the low Q fj\ 109-6(11 VN / \ 1.246 IB „ temperature structure is incommensurate with a i-soei6) modulation along the four-fold a.xi^.l Below the 'l-265(2> transition temperature, the sinusoidal distortion which modulates the Br ion positions reduces the actinide ion site symmetry from Dgd to Dj. How ever, it has been shown from spectral singulari ties of U'l+:ThBr4 by absorption spectroscopy that some of the impurity ions pin the phase of the mod ulation and are in Dgd sites. Studies of Pa*+ in Fig. 7.1. Bond distances (A) and angles (deg) in ThBro by optical spectroscopy have been undertak the edta moiety, averaged for the 3 to 12 chemi en to further study the crystal field effects of cally equivalent bonds in the Pr, Sm, and Gd the incommensurate structure on the 5f* config salts. (XBL 8112-13065) uration and to compare the derived parameters with earlier work on Pa4+ in ThCl4.2 Electron

paramagnetic resonance (EPR) studies described in 4 ThBf4 i Pti * this article provide information about the ground T.KHC j.3/2 state of Pa4+ diluted in ThCl^ and ThBr4. The re sults of these measurements will be presented. . The absorption and emission spectra of 4+ ' \-l Pa :ThBr4 closely resembled the spectra 4+ 2 r previously reported for Pa :ThCl4. At 77 K, four absorption bands were observed between 1480 nm and 1870 nm for Pa4*:ThCl4 and between 1540 nm 4+ and 1870 nm for Pa :ThBr4. The peculiar line Tna» ,Po*v<) shapes observed for the zero-phonon transitions 4 can be explained by the incommensurate structure of the host crystal, ThBr^, below 95 K. In the pure material, the sinusoidal modulation of the Br ion positions along the four-fold high symmetry axis reduces the metal ion site symmetry from 4+ D2tj to D2. In the diluted crystal, the Pa °v impurity forces the local symmetry (at some Pa^+ rK sites) to remain DM. Therefore the symmetry at the Pa^+ sites vanes from 0?^ at one extreme to the maximum D? distortion at the other. The line Fig. 1.2. (A) Experimental EPR spectrum for shape 'chan follows a continuous variation which Pa4+:ThBr*. (B) Calculated EPR spectrum foi reflects the shift of the energy levels as the Pa4n.a+.TLn+:ThBr^ tvnt(XBL Oi831-7600l -len.W) symmetry changes. This variation which is shown in Fig, 1.1 for the IT spectra (E || C), can be described as a continuum of absorption lines found for these samples which suggest that the deviations from D j symmetry do not greatly between two sharp edges. Similar peak shapes 2t were obtained for Pa^+:ThCl4 which confirms the affect the magnetic properties of the g-ound state. Nevertheless, the experimental'spectra, postulated modulated structure for this host ma 4+ terial as determined by nuclear quadrupole res especially Pa :ThCl4, show a marked anisotropy onance spectroscopy.3 of the line width which increased when the mag netic field is perpendicular to the highest sym metry axis. The increase in line width in this 4+ plane could be because of the decrease in sym The EPR spectra of powders of Pa :ThBr4 (Fig. D 4+ metry from D d to for the modulated struc 1.2) and Pa :ThCl4 are almost identical and 2 2 ture which should split into g and g«. Single clearly show that the g and A tensors are almost gL x isotropic. Relatively narrow line widths are crystal EPR data for the x,y-plane are necessary to confirm the above hypothesis.

Th &4 : Pa* •* 4 2 K CTs;id TI polomed spectra tBrief version of LBL-15084. 1. L. Bernard, R. Currat, P. Delamoye, C. Zeyen, S. Hubert, and R. de Kouchkovsky, J. of Physics C, in press. 2. J. C. Krupa, M. Hussonnois, M. Genet, and R.

Guillaumont, J. Chem, Pnys. 77_y 154 {1982). 3. C. Khan Malek, A. Peneau, L. Guebe, P. Delamoye, and M. Hussonnois, J. Molec. Struc., in press.

2. FOURIER TRANSFORM SPECTROMETRY OBSERVATIONS OF THE ACTINIDES

J. G. Conway, E. F. Worden, •). Brault, R. Hubbard, and J. Wagner As part of a continuing national effort rn the classification of the free ion spectra of the actinide elements, the spectrum of uranium in the wavelength region of 2 to 5 H in a water-cooled hollow cathode source has been analyzed. Over 5000 lines have been assigned to transitions be tween known energy levels of U I and U II. The tolerance between the observed and calculated Fig. 1.1. Influence of the incommensurate struc levels is 0.005 cm-1. About 4000 lines remain ture of ThBr4 on the Pa4"1- absorption band shapes unassigned. Uranium has also been observed in at 4.2K. The shaded peak i", typical. the wavelength region from 2500 A to 2 u in the {XBL 831-759Q) same source. 205

The spectra of Z40pUj 241flm, 242mAm> and 244ftn t9. 0. H. Templeton and L. K. Templeton, "X-Ray have also been measured in the wavelength region Oichroism and Polarized Anomalous Scattering of of 1 u to 2500 A using an electrodeless discharge the Uranyl Ion," Acta Cryst. A38, 62 (1982);

lamp. The spectrum of 243/^ nas already been LBL-12477. measured by Frank Tomkins of Argonne National Laboratory and is available for analysis. +10. L. K. Templeton, D. H. Templeton, R. P. Phizackerley, and K. 0. Hodgson, "L3-Edge All measurements were obtained on the Kitt Anomalous Scattering by Gadolinium and Samarium Peak National Observatory Fourier transform Measured at High Resolution with Synchrotron Ra optical spectrometer using a variety of beam diation," Acta Cryst. A38, 74 (1982): LBL-12825. splitters. The intensity response of the spectrometer was determined with standard 11. T. D. Tilley, R. A. Andersen, A. Zalkin, and radiance lamps and calibrated argon miniarcs. D. H. Templeton, "Bis(pentamethylcyclopentadienyl)carboxylato and Dithiocarbamato Derivatives of Neodymium(III) and Ytterbium (III). Crystal Structure of Bis(pentamethylcyclopentadienyl)- Diethyldithiocarbamato Ytterbium(III)," Inorg. Chem. 21, 2644 (1982). 1982 PUBLICATIONS AND REPORTS 12. T. D. Tilley, R. A. Andersen, B. Spencer, and Refereed Journals A. Zalkin, "Crystal Structure of Bis(pentamethyl- cyclooentadienyl) Bis(Pyridine)-Ytterbium(II)," 1. T. D. Tilley and R. A Andersen, "Preparation Inorg. Chem. 21, 2647 (1982). and Crystal Structure of Bis[bis(pentamethylcyclopentadienyl)ytterbium(III)] Undecacarbonyl- 13. i. L. Robbins, N. Edelstein, B. Spencer, and triferrate, [(Me5C5)2Yb]2[Fe3(C0)xi]; A Compound J. C. Smart, "The Synthesis and Electronic Struc with Four Isocarbonyl (Fe-CO-Yb) Interactions," tures of Decamethylmetallocenes," J. Am. Chem. J. Am. Chem. Soc. 104, 1772 (1982); LBL-13612. Soc. 104, 1882 (1982).

2. T. 0. Tilley, R. A. Andersen, and A. Zalkin, 14. K. Abu-Dari and K. N. Raymond, "Spe "Tertiary Phosphine Complexes of the f-Block cific Sequestering Agents for the Actinides.

Metals; Crystal Structure of Yb[N(SiMe3)2]2- 8. Synthesis and Structural Chemistry of [MejPCHjCHjPMe?]: Evidence for a Ytterbium-r- Tetrakis(thiohydroxamato)hafnium(IV) in

Carbon Interaction," J. Am. Chem. Soc. 104, 3725 Hf(CH3C6H4(S)N(0)CH3)4-C2H50H," Inorg. Chem. (1982); LBL-14025. 21, 1676 (1982); LBL-13173.

3. A. Zalkin, D. H. Templeton, W. D. Luke, and *15. V. L. Pecoraro, G. B. Wong, and K. N. A. Streitwieser, Jr., "Synthesis and Structure of Raymond, "Gallium and Indium Imaging Agents. Dicyclopentanouranocene, U[C8Hs(CH2)3]2," Organo- 2. Complexes of Sulfonated Catechoylamide metallicsj., 618 (1982); LBL-13216. Sequestering Agents," Inorg. Chem. 21, 2209 (1982). — 4. D. L. Perry, A. Zalkin, H. Ruben, and D. H. Templeton, "Synthesis, Characterization, and *16. C. W. Eigenbrot, .>. and K. N. Raymond, Structure of a Uranyl Complex with a Disulfide "Organouranium Complexes of Pyrazole and Ligand, Bis(di-n-propylammonium)adisulfidobis Pyrazolate. Synthesis and X-Ray Structures of

(di-n-propylmonothiocarbamato)Dioxouranate(vT)," U(C5Me5)2Cl2(C3H4N2), U(C5Me5)2Cl(C3H4N2), and

Inorg. Chem. 2J_, 237 (1982); LBL-10654. U(Ci;Me5)-(C3H3N2)2," 'norg. Chem. 21, 2653 (19d2); LBL-13070. — 5. A. Zalkin, H. Ruben, and D. H. Templeton,*&ft "The Structure of Nickel Uranyl Acetate Hexa- 17. C. W. Eigenbrot, Jr. and K. N. Raymond, hydrate," Acta Cryst. B38, 610 (1982); LBL-12551. "Crystal and Molecular Structure of

[Nd(tren)2(CH3CN)](C104)3," Inorg. Chem. 6. J. 0. Arenivar, V. V. Mainz, H. Ruben, R. A. 21, "S67 (1982); LBL-13075. Andersen, and A. Zalkin, "Stereochemistry of Bis(carboxylato)Bis(chloro)8is(tertiary phos *18. S. M. Moerlein, M. J. Welch, and K. N. phine) Dimolybdenum Complexes; Crystal and Mo Raymond, "Use of Tricatechol amide Ligands to lecular Structures of Two Isomers of (Me3CC02)2 Alter the Biodistribution of Gallium-67: Concise

(PEt3)2M02," Inorg. Chem. 21, 2649 (1982); Communication," J. Nucl. Med. 23, 501 (1982). LW.-13381. *19. M. J. Kappel and K. N. Raymond, Verric Ion 7. T. Hayhurst, G. Shalimoff, J. G. Conway, Sequestering Agents. 10. Selectivity of Sul N. Edelstein, L. A. Boatner, and M. M. Abraham, fonated Poly(catechoylamides) for Ferric ion," "Optical Spectra and Zeeman Effect for Pr3+ and Inorg. Chem. 21, 3437 (1982); LBL-14680. Nd3+ in LUPO4 and YPO4," J. Chem. Phys. Ti, 3960 (1982); LBL-13388. *20. S. R. Cooper, Y. B. Koh, and K. N. Raymond, "Synthetic, Structural, and Physical Studies of 8. L. K. Templeton, D. H. Templeton, A. Zalkin, Bis(triethylammonium) Tris(catecholato)vana- and H. Ruben, "Anomalous Scattering by Praesody- date(IV), Potassium Bis(catecholato)oxovana- mium, Samarium and Gadolinium, and Structure of date(IV), and Potassium Tris(catecholato)- Ethyldiamminetetraacetate Salts," Acta Cryst. B38, vanadate(III)," J. Am. Chem. Soc. 104, 5092 2155 (1982); LBL-13866. (1982). 206

LBL Reports 2. R. A. Andersen, "Phosphine Complexes of the Actinide Metals," University of California, Davis, 1. R. Shinomoto, E. Gamp, N. Edelstein, D. H. California, October 17, 1982. Templeton, and A. Zalkin, "Synthesis and Crystal Structures of the Tetrakis{methyltrihydn»orato) 3. D. H. Templeton, "Anomalous X-Ray Scattering," Compounds of Zirconium(IV), Thorium(IV), Urani- a series of six lectures, University of Lausanne, um(IV) and Neptunium{IV)," submitted to Inorg. Switzerland, October 27-December 1, 1982. Chem., LBL-15090. 4. D. H. Templeton, "Anomalous Scattering of 2. T. D. Til ley, R. A. Andersen, and A. Synchrotron Radiation," University of Paris, Zalkin, "Tertiary Phosphine Complexes of the France, October 5, 1982; University of Berne, f-Block Metals; Preparation of Pentamethylcyclo- Switzerland, November 19, 1982; University of pentadienyl-Tertiary Phosphine Complexes of Yb(II Neuchatel, Switzerland, November 29, 1982; and and III) and Eu(II). The Crystal Structure of Federal Technical University, Zurich, Switzerland, YblMesCcJjCHMejPCHjPMe?)," submitted to Inorg. December 9, 1982. Chem., LBL-14367. 5. N. M. Edelstein, "Measurement of Formation 3. S. A. Kinsley and A. Streitwieser, Jr., "Di- Constants and Solubilities of Actinide Ions in potassium Bis-([8]Annulene)-Ytterbium(II) and Neutral Solution," Institute for Inorganic Chem Bis-([8]Annulene) Calcium, LBL-15018. istry, Free University, Berlin, U. Germany, June 3, 1982. 4. R. P. Planalp, R. A. Andersen, and A. Zalkin, "Oialkyl Bis[Bis(Trimethylsilylamideo] Group IV A 6. N. M. Edelstein, "Synthetic and Spectroscopic Metal Complexes; Preparation of Bridging Carbene Studies^on Actinide Halides and Borohydrides," Complexes by y-Elimination of Alkane. Crystal Centre Etudes Nucle"aires, Saclay, France, June

Structure of {ZrCHSi(Me)2NSiMe3-[N(SiMe3)2]2 } 2," 30, 1982. LBL-14754. 7. J. G. Conway, "Atomic Spectroscopy of Actin 5. N. M. Edelstein and J. Goffart, "Magnetic ide Elements," Institute of Atomic Energy, Beij Properties of the Actinides," to be published in ing, China, April 6, 1982; Institute of Modern The Chemistry of the Actiniae Elements, J. J. Physics, Lanzhou, China, April 12, 1982; and Katz, G. T. Seaborg, and L. R. Morss, Eds., institute of Nuclear Research, Shanghai, China, Chapman and Hall Ltd., London, LBL-14195. April 16, 1982.

Other Publications 8. J. G. Conway, "Laser Spectroscopy of Rare Earths and Actinides," Institute of Atomic 1. Actinides in Perspective, N. M. Edelstein, Energy, Beijing, China, April 7, 1982. Ed., Pergamon Press, Oxford, 19B2. 9. J. G. Conway, "Absorption Spectra of Actinide 2. K. N. Raymond and T. P. Tufano, "Coordination Ions in Crystals," Institute of Atomic Energy, Chemistry of the Siderophores and Recent Studies Beijing, China, April 7, 1982. of Synthetic Analogues," in The Biological Chem istry of Iron, H. B. Dunford, D. Oolphin, K. N. 10. J. G. Conway, "Spectroscopy in China," Raymond, and L. Seiker, Eds., D. Reidel Publishing Northern California Section, Society for Applied Company, Dordrecht, Holland, 1982, pp. 85-105. Spectroscopy, University of California, Berkeley, September 16, 19B2. 3. K. N. Raymond, M. J. Kappel, V. L. Pecorai-o,

W. R. Harris, C. J. Carrano, F. L. Weitl, and R. 11. A. Streitwieser, Cir.t "New Developments in W. Durbin, "Specific Sequestering Agents for Ac Uranocene Chemistry," University of Wisconsin, tinide Ions," in Actinides in Perspective, N. H. Sprague Lectures, Madison, Wisconsin, May 7, Edelitein, Ed., Pergamon Press, Oxford and New 1982; Tel Aviv University, Tel Aviv, Israel, York, 1982, pp. 491-507. Sackler Lectures in Chemistry, October 26, 1982; and Ben Gurion University of Negev, Beersheva, 4. K. N. Raymond, V. L. Pecoraro, W. R. Harris, Israel, October 27, 1982. and C. J. Carrano, "Actinide Coordination and Discrimination by Human Transferrin," in Environ 12. K. N. Raymond, "The Coordination Site and mental Migration of Long-Lived Radionuclides, In Fe(III) Exchange Processes for Transferrin and ternational Atomic Energy Agency, Vienna, 1982, Siderophores," 65th Canadian Chemical Conference pp. 571-577. and Exhibition, Toronto, Canada, May 30-June 2, 1982. 5. G. T. Seaborg, "The Plutonium Story," in Actinides in Perspective. N. M. Edelstein, Ed., 13. K. N. Raymond, "Synthesis and Properties of Pergamon Press, 1982. Iron(III) and Actinide(IV) Specific Sequestering Agents," 37th Annual Northwest Regional Meeting Invited Talks of the American Chemical Society, Eugene, Oregon, June 17-18, 1982. 1. R. A. Andersen, "Electron Transfer Properties of Lanthanide(II) Complexes," 2nd Homogeneous 14. K. N. Raymond, "The Iron Coordination Site Catalysis Research Conference (DOE), Madison, and Metal Ion Exchange Kinetics of Transferrin Wisconsin, June 7-9, 1982. and Lactoferrin," ACS Pacific Conference on Chem- 207

istry and Spectroscopy, San Francisco, California, sity of Southern California, Los Angeles, Cali October 27-29, 1982. fornia, October 5, 1982.

15. K. N. Raymond, "Coordination Chemistry of 17. G. T. Seaborg, "40 Years of Plutonium Chem Biological Iron Transport Compounds," Oregon istry: The Beginnings," Meeting of the American Graduate Center, Beaverton, Oregon, February 1, Chemical Society, Kansas City, Missouri, September 1982; University of Texas, Austin, Texas, April 13, 1982. 22, 1982; University of Houston, Houston, Texas, April 23, 1982; Princeton University, Princeton, 18. G. T. Seaborg, "The Transuranium Elements," New Jersey, April 28, 1982; Columbia University, Symposium on 50th Anniversary of the Discovery of New York, New York, April 29, 1982; Yale Univer the Neutron, Cambridge University, Cambridge, sity, New Haven, Connecticut, April 30, 1982; England, September 16, 1982. Harvard University, Cambridge, Massachusetts, May 3, 1982; and Polaroid Corporation, Cambridge, * * * Massachusetts, May 4, 1982. tpartially supported by the National Science Foundation. 16. K. N. Raymond, "Microbial Iron Chelating (•Partially supported by the National Institutes Agents—Their Recognition and Transport," Univer of Health. Fossil Energy 209

Fossil Energy a. Electrode Surface Chemistry* Phillip N. Ross, Jr., investigator

Introduction. Commercialization of phosphoric acid fuel ceil technology requires a capital cost reduction and an extension of power plant life PIC I 115 compared to currently available technology. Sig nificant capital cost reduction can be achieved if an oxygen reduction catalyst that is catalytically more active than platinum can be developed. The objective of the present research is to de velop the physical and chemical understanding of the oxygen-platinum surface interactions necessary for the rational selection of alloying ligands that modify the basic catalytic properties of platinum. It is felt that the platinum-oxygen bond energy will be changed when ligands are bonded to the surface plati-umi atoms and that, by the use of appropriate ligands, an optimal bond energy will result in enhanced catalytic activity relative to the pure platinum surface. ptciee? Previous work in this program has shown that supported bimetallic catalysts employing Ti, Zr or Ta in addition to Pt produced enhanced activi ty for oxygen reduction. It was not clear in that work how the Pt and the base metal were associated on the support, although there was some evidence by x-ray diffraction of alloy for mation. The focus of the present research is to determine the manner in which the base metal mod ifies the catalytic properties of Pt by the use of ordered (single crystal) intermetallic solid electrodes well-characterized by the techniques of contemporary surface science (LEED, AES, XPS). 575 675 775 875 TEMPERATURE CfO 1. HIGH COVERAGE STATES OF OXYGEN ON Pt{001) AND Fig. 1.1. Thermal desorption spectra for Pt(lll) (lll)t and Pt(100) after: {a} high pressure, high temperature dosing; (b) room temperature dosing. G. Derry and P. N. Ross, Jr. Scale for (100) reduced by a factor of 2. (XBL 831-7641) Oxygen chemisorption on the Pt(lll) and Pt(001) surfaces was studied for various surface temperatures and oxygen pressures. These studies were carried out in an ultrahigh vacuum chamber ture near ambient (<370 K), a dissociated adsorbed with capabili+y for x-ray and uv photoelectron species forms on both the Pt(lll) and Pt(100) spectroscopy, and thermal desorption spectros crystal faces. Saturation coverage on Pt(lll) copy. The electron spectrome+er is of the angle- was ~0,25 ML, somewhat greater than for Pt(100) resolving hemispherical type, allowing variable (-0.2 ML). The thermal desorption of the low surface sensitivity by varying the take-off angle. temperature species on both surfaces can be repre sented by second order Arrhenius kinetics. Expo Thermal desorption results for several typical sure at elevated surface temperature (~570 K) and exposures are presented in Fig. 1.1. If the oxy higher oxygen pressure (-10"3 Pa) resulted in gen pressure is ~10-5 Pa and the surface tempera- the formation of higher coverage states (both conditions are necessary). The saturation cover age on Pt(lll) increased by about a factor of 2, and the desorption lineshape developed an asym metry on the low temperature side. For Pt(100), -This work was supported by the Assistant the saturation coverage increased by a factor of Secretary for Fossil Energy, Office of Coal Fuel 4-5 and the desorption lineshape developed a com Cells, Advanced Concepts Divi'"on of the U.S. plex structure. Arrhenius kinetics no longer Department of Energy under Contract No. describe these thermal desorption spectra. XPS OE-AC03-76SF00098 through the Fuel Cell Project indicated the binding energy of the 01s core Office, NASA Lewis Research Center, Cleveland, Ohio. level was 0.4 eV lower for the higher coverage 210

state on Pt{100) than for the low coverage state. of the annealed ZrOx on Pt surface appears to be For oxygen on Pt(lll), the 01s binding energy was analogous to the SMSI effect reported1 for Pt the same for both high and low coverage. UPS dispersed on T1O2. from the valence band was consistent with these 01s XPS results. The new features that appear in the Pt,valence band upon adsorption of oxygen on Pt(lll) differed only in magnitude between the +Brief version of LBL-15294. high coverage and low coverage states. The high *This work was also supported by the Director, coverage state on Pt(lOO), however, produced a Office of Energy Research, Office of Basic Energy new feature in the UPS spectrum just below the Sciences, Materials Sciences Division of the U.S. Fermi level which was not observed for the low Department of Energy under Contract No. coverage state. DE-AC03-76SF00098. 1. S. Tauster and S. Fung, J. Catal. 55, 29 From these data, we deduce that the high (1978). coverage state of oxygen on Pt(lOO) is a new state chemically distinct from the low coverage state. On Pt(lll), however, the low coverage and 3. ADSORPTIVE AND CATALYTIC PROPERTIES OF f high coverage states are chemically the same. POLYCRYSTALLINE Pt3Ti Variable take-off angle 01s spectra indicated that the high coverage states are still on the surface, U. Bardi, P. N. Ross, Jr., and G. Somorjai not below the surface. Our observation of both high and low coverage states forming under differ Polycrystalline Pt3Ti was prepared by arc ent conditions of temperature and pressure recon melting the pure metals in an argon atmosphere. ciles previously contradictory reports in the A clean surface, defined by Auger electron spectra literature for oxygen adsorption on Pt{100). {AES) that show only lines characteristic of Pt and Ti, could be produced by ion bombardment and thermal annealing in ultrahigh vacuum. Analysis of AES Pt/Ti peak height ratios indicated that "•"Brief version of LBL-15231. the clean vacuum annealed surface is enriched in Pt. Thermal desorption (TDS) studies of carbon monoxide and hydrogen were conducted on the clean 2. ADSORPTIVE AND CATALYTIC PROPERTIES OF annealed surface, and on the same surface covered ZIRCONIUM OVERLAYERS ON Pt(001)ft by an evaporated Pt overlayer. As shown in Fig. 3.1, the carbon monoxide TDS peak from the Pt3Ti U. Bardi, P. N. Ross, Jr., and G. Somorjai surface was shifted ca. 60 K lower in temperature, with about 60-70% of the coverage, from the peak Metallic zirconium was deposited on a [001] for the pure Pt surface. This shift is inter oriented substrate by electron beam evaporation preted as a ligand effect on the Pt because of in UHV conditions. LEED and AES were used to the strong intermetallic bonding that occurs in characterize the surface structure and composi this intermetallic compound. Qualitatively simi tion, thermal desorption was used to obtain lar effects were observed in hydrogen thermal information on the adsorbed species, and low desorption spectra. Essentially no chemisorption pressure (P = 10~5, 10~6 torr) catalysis experi of either hydrogen or carbon monoxide was observed ments were used to characterize the catalytic when the surface was pre-treated in oxygen at properties of the surface. The zirconium overlayer was observed to grow on the Pt surface at room temperature by the layer-by-layer mechanism. Zirconium on platinum was found to react readily with oxygen, carbon monoxide, and hydrocarbons COexposuraHOL forming overlayer oxides on carbides, respective ly. Thermal annealing in UHV at T > 900 K caused I Pt decomposition of these overlayers and dissolution of zirconium into the bulk. A surface that was annealed after metallic zirconium deposition 3Pt Ti oxidized reacted more slowly with oxygen, but eventually 3 equilibrated to form the same surface phase as obtained by annealing the oxide overlayer. Sev eral ordered structures were observed by LEED after annealing, which depended on the amount of zirconium deposited and the oxygen content in the surface. The presence of these ordered structures E indicates that the Pt-Zr interaction remains O strong even when the zirconium is oxidized, pro bably indicative of the formation of a Pt-ZrOx surface compound. The adsorptive properties of these surface compounds were observed using CO and O2 as "probe" molecules. The TDS results 300 400 500 600 700 800 indicated that: (a) the Pt-ZrO surface has a Pt x Temperature (K) enriched top layer with a ZrOx underlayer; (b) a ligand effect from the Pt-Zr bond reduces the Fig. 3.1. Thermal desorption spectra for CO on Pt-CO and Pt-0 bonding interactions. The behavior polycrystalline Pt3Ti relative to polycrystalline Pt. (XBL 8211-4657) 211

elevated temperature. Based on these TDS observa 2. U. Ejrdi, P. N. Ross, Jr., and G. Somorjai, tions, one would expect dramatically different "Structure and Composition of Annealed Zirconium behavior of Pt3Ti than for pure Pt in CO/H2 reac Overlayers on Pt(OOl)," submitted to J. Vac. Sci. tions. In oxidizing environments, however, Pt3Ti Tech., LBL-15294. appears to have only negative characteristics relative to pure Pt. 3. U. Bardi, p. N. Ross, Jr., and G. Somorjai, * * * "Ligand Effects in CO Chemisorption on Poly- crystalline PtjTi," submitted to J. Catal., ^This work was also supported by the Director, LBL-15603. Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy under Contract No. 4. U. Bardi, G. Somorjai, and P. N. Ross, Jr., DE-AC03-76SF00098 "Adsorption and Catalysis on Zirconium Overlayers on Pt(OOl) Surfaces," LBL-15604.

1982 PUBLICATIONS AND REPORTS Other Publications LBL Reports 1. P. N. Ross, Jr., "Studies of Adsorption at 1. G. Derry and P. N. Ross, Jr., "High Coverage Well-Ordered Electrode Surfaces Using LEED," in States of Oxygen Adsorbed on Pt(OOl) and (111) Chemistry and Physics of Solid Surfaces IV. Surfaces," to be published in Surf. Sci., edited by R. Vanselow and R. Howe, Springer- LBL-15231. Verlag, 1982, p. 173-200. 212

b. Studies of Material* Erosion/Wear In Coal Convention System!*

Alan V. Levy, Investigator

1. THE HIGH TEMPERATURE EROSION OF DUCTILE weight for 310SS. A roughly parabolic curve is ALLOYS7 shown for the 30* impingement angle tests with a flat portion of 0.4 x 10-4 g/g occurring up to Jennifer Patterson and Alan Levy a temperature of approximately 400*C. A similar result was obtained for^304SS with a minimum Erosion tests were conducted in inert gas occurring at 0.51 x 10"^ g/g. Above 400*C the atmospheres at elevated temperatures in order to erosion rate increased rapidly for both alloys. determine the effect of temperature on the erosion At an impingement angle of 90 , the 310SS curve process in metals without corrosion also occurring. shows a decrease in the erosion rate with temper The interpretation of combined erosion-corrosion ature to a minimum at 400*C. The behavior of the data from elevated temperature exposures is aided alloy at both impingement angles can be explained by the erosion-only data developed in this task. by the platelet mechanism of erosion. At 800*C, the erosion rate was determined for several veloc The materials tested were 304 and 310SS. The ities and was found to increase with erodent par materials were eroded by 300 gm of 55 ym silicon ticle velocity. carbide particles at a velocity of 30 m/s. Nitro gen was used as the carrier gas. The tests were conducted at 25"C through 90O°C and 90' and 30° "^Brief version of LBL-15655. particle impingement angles.

In Fig. 1.1, the steady state erosion rate is 2. METHODS FOR CHARACTERIZATION OF EROSION BY presented as a function of erodent particle GAS-ENTRAINED SOLID PARTICLES1" Jennifer Patterson and Alan Levy 0.2 ! 1 The experimental techniques used in the 310 SS incremental type of erosion testing of ductile _ 0.18 240/wm SiC metals have been studied in order to optimize V= 30 mps them. The areas addressed in this investigation 1 0.16 were specimen preparation, erosion testing, and Run data analysis. Criteria for the preparation of '• 1 metal specimens used in gas-solid erosion testing if 0.14 D 2 / were established. The detailed steps in erosion o 3 testing were assessed and standardized. The var < /a=30° ious measurements of solid particle velocity were -CT 0.12 O 4 evaluated. An analysis was made of characteristic errors in erosion rates measurement and methods of Y o.i - reducing these errors were developed. o Identical erosion experiments using two clean x 0.08 ing methods, wiping with a tissue and ultrasonic -S? 0 cleaning in alcohol, resulted in a 38* lower ero o / sion rate using the tissue cleaning method because 2 0.06 Ao/ of residual erodent on the specimen surface that c protected it from subsequent erosion exposures. •§ 0.04 ztL^y•, A a=90° Because of inherent small errors in measurement /m of weight differences of <1 mg that occur in in ^0.02 cremental erosion testing, a method of handling ^^**aft*_^-^» j» *A \4 a T^-K^ • the data was developed that did not utilize finite i 1 difference of before and after weights. A differ °-°0 200 400 600 800 1000 entiation of the curve of incremental weight of the specimen vs the amount of eroding particles results in incremental erosion rate curves which Temperature (°C) have markedly less scatter than those generated using the finite difference method. Fig. 1.1. Erosion rates of 310SS at elevated temperatures. (XBL 827-7092) +Brief version of LBL-15017. *Research sponsored by the Department of Energy under DOE/FEAA 15 10 0, Advanced Research and Technical Development, Fossil Energy Materials Program, Work Breakdown Structure Element LBL-3.5 and U.S. Department of Energy under Contract Nn D5-AC03-76SF00098. 3. EFFECT OF PARTICLE VELOCITY OK THE PLATELET the erosion rate of the 1020 steel increased from MECHANISM OF EROSION^ 0.2 x 10"5 cc/g to 9.5 x 10-5 cc/g because much larger platelets were formed and removed. A num Mostafa Aghazadeh and Alan Levy ber of steel and aluminum alloys responded simi larly to AI2O3 and SiC erodent particles. Larger The erosion of ductile metals in gas-solid platelets were formed at a 30" impingement angle particle streams varies exponentially with parti than at a 90* angle with a corresponding increased cle velocity. This effect has been reported in erosion rate. the literature for many years and used in erosion mechanism models. The validity of the platelet mechanism of erosion was determined over a range of velocities. "f*Brief version of LBL-15656. Increasing the velocity from 30 to 130 m/s was found to increase the size of the craters and 4. EROSION OF BORIDE COATINGS1" resulting platelets formed while the mechanism remained the same. Figure 3.1 shows the cross Mostafa Aghazadeh and Alan V. Levy section of 1020 steel after being eroded at 30 m/s and 130 m/s with silicon carbide particles. Over The operation of metal surfaces subjected to the relatively large range of test velocities, severe abrasive or sliding wear has been aided by the application of hard materials to the wear surface. The potential of protection of sub strates by hard facing materials in erosive wear was investigated using a family of Ni-Cr-B alloys with large percentages of hard, second-phase boride particles in the nickel matrix.

The erosion of the hard facing alloys was determined as a function of composition, morphol ogy, and method of application on a mild steel substrate. Several important relationships were determined between the material variables and their erosion rates. Unlike abrasive wear v-fiere the eroding particles are held in position as they translate across the eroding surface, in gas-solid particle impact erosion, the quantity of boride hardening phase in the alloy (»40£ to 40%) and the resultant hardness have very little effect on the erosion rate. Tfie addition of hard tungsten carbide particles to one of the alloys to further harden it even resulted in a signifi cant increase in the erosion rate.

The erosion rate was determined to increase with increasing random porosity in the coating. Figure 4.1 shows the cross sections of a nickel- boron alloy deposited on the mild steel surface by three different processes. The dense, braze- coat alloy had an erosion rate of 5.37 x 10-6 cc/g. The same alloy in the flame sprayed form had an erosion rate of 6.08 x 10-6 cc/g, while the most porous form of the alloy, the plasma sprayed coating, had an erosion rate of 6.44 x 10-6 cc/g. Much knowledge is being developed by these tests that will aid alloy selection and

I0i.m_ refinement for service in erosive environments. * * * Fig. 3.1. Cross section of eroded 1020 steel surfaces at V = 30 and 130 m/s.

Flame Spray Plasma Spray

50 urn 50 urn Fig. 4.1. Cross sections of uneroded nickel alloy, AMS 4779 Ni-B. (XBB 827-6203)

5. EROSION-CORROSION OF STEELS IN A BURNER DUCT was exposed to the erosive-corrosive environment TEST DEVICE1" at 900 C.

Elliot Slamovich and Alan Levy At the test conditions used, corrosion was the dominant mechanism. The individual crystals The combined erosion-corrosion of low alloy shown in both the corroded and eroded-co.-roded and stainless steels in air was determined using photos were identified as iron oxide by Raman the ACES exhaust gas burner facility at the Sandia spectroscopy. The great difference in the mor National Combustion Research Center. The purposes phologies of the two sides is indicative of the of the project are to: (1) determine the morphol complexity of the combined erosion-corrosion ogy of the eroded-corroded surfaces compared to mechanism. The enhancement of crystal growth as only corroded and only eroded surfaces, (2) deter the result of a selective removal of the iron mine the mechanism of simultaneous erosion- oxide crystals by the erosion process is clearly corrosion, and (3) examine the conditions under seen as is the erosion of the tops of the crys which corrosive or erosive attack on the alloy tals to form a point. The same effect was also dominates. observed in the other chromium bearing alloys tested. The ability of the brittle iron oxide Tests have been run on cubes of several steels crystals to resist being completely removed by ranging in chromium content from 0-18%. They the impact of the eroding particles and to grow to such a large size compared to the corroded- were eroded by 5 vm diameter fly ash at 15 m/s in an oxygen rich, combusted propane-air stream at only side crystals indicates that new mechanisms 700 to 1000°C. The samples were mounted to expose of erosion of brittle scales must be considered. two faces of the test cube to the particle flow and two faces to just the corrosive gases. Thus, corrosion behavior was determined simultaneously with the combined erosion-corrosion behavior in a +Br1ef version of LBL-15657. single specimen. The 410SS specimen (Fig. 5.1) 215

Corroded Eroded-Corroded 10 um 20 um

Corroded Eroded-Corroded 3 pm 3 pm

Fig. 5.1. Surface of corroded and eroded-corroded 410SS. (X8B 8210-9325)

6. EROSION OF METALS IN LIQUID SLURRIES1" steels. The 4340 has a tensile strength of 100 ksi and an elongation of 25% while the 1020 Paul Yau and Alan Levy steel has a lower tensile strength of 57 ksi and a higher elongation of 36%. Both steels eroded The erosion of low alloy steels was determined similarly at the higher impact angles while the at 25°C over a range of velocities and impingement less ductile 4340 eroded somewhat more at the angles using 30 wt.% -200 mesh coal in kerosene lower impact angles. The reason for the differ slurries. The slurry and test conditions simu ence in the relative amount of erosion between lated part of the conditions that exist in the the alloys at lower and higher impingement angles slurry mixing area of a direct coal liquefaction was related to the lubricating nature of the non process plant. aqueous fluids in the slurries.

4340 steel was tested at 3oheat treat conditions: as-quenched, 200"C temper, and r i ~i r i spheroidize annealed. 1018 plain carbon steel was tested in the hot-rolled and spherodize- * Spherodizid 4340 steel annealed conditions. It was determined that, in o Spherod.ied 1020 steel general, the greater the ductility of the heat 30 wt*/. coal, 200 mesh , in kerosene treated alloy, the lower the erosion rate. The Velocity 13 mps 4340 in the as-quenched condition with an elonga Temp 25° C tion of 8% tiroded 3 to 4 times as much as 4340 in the spheroidize-annealed condition with an elonga tion of 25£, depending on the impingement angle. The effect of velocity on the erosion rate of hot-rolled 1018 steel was determined for a range of velocities from 10 to 30 m/s. aThe velocity exponents varied from 2.0 at a 2U° impingement angle to 1.6 at a 90° impingement angle. Angle of impingement (deq) Figure 6.1 shows the effect of impingement Fig. 6.1. Erosion rate of spheroidized 4340 and angle on erosion for spberoidized 4340 and 1020 1020 steel in coal-kerosene slurry. (X8L 8211-7300} 216

3. A. Levy and 6. Hickey, "Surface Degradation * * * of Metals in Simulated Synthetic Fuels Plant Environments." Paper no. 154, NACE Corrosion 8?. +8rief version of LBL-15658. Houston, Texas, March 1982.

7. CORROSION OF METALS IN OU SHALE RETQRTS+ 4. M, Landkof, D. Boone, D. Whittle, and A. Levy, "Protective Coating Systems for Use in Combustion Elliott Slamovich and Alan Levy Gases," Paper no. 287, NACE Corrosion 82, Houston, Texas, March 1982. An investigation of metallic corrosion in the oxidizinq and sulfidizing environments of oil 5. A. Levy and E. Slamovich, "Elevated Tempera shale retorts has been completed. Both the cor ture Corrosion of Steel Alloys in Oil Shale rosion environments of underground in-situ and Retorting Environments," Proceedings of Electro above-ground retorts were investigated. Test chemical Society Conference on Corrosion/Energy samples were exposed in large retorts of both Technology, Paper no. 113, ECS Annual Fall Meet types. The effect of chromium content in commer ing, Detroit, Michigan, October 1982. cial steel alloys exposed to in-situ retorting environments was determined using a small labora LBL Reports tory crucible containing Green River shale at a test temperature of 980 C. 1. J. Patterson and A. Levy, "Elevated Temperature Erosion of Alloys," L8L-15655. It was determined that different patterns of corrosion, external and internal, occurred for 2. J. Patterson and A. Lrvy, "Methods for each alloy exposed to the same test conditions. Characterization of Erosion of Gas-Entrained Higher chromium content alloys had lower external Solid Particles," LBL-15017. corrosion. However, the presence of chromium promoted internal corrosion. The chromium free, 3. M. Aghazadeh and A. Levy, "The Effect of 1018-mild steel had extensive external corrosion Particle Velocity on the platelet Mechanism of but no internal corrosion. The 2 l/4Cr and 5Cr Erosion," LBL-15656. cintaining steels formed internal iron sulfides wi.T IO the 9Cr and austenitic stainless steels 4. A. Levy, T. Bakker, E. Sholz, M, AghazaJeh, were internally oxidized. The occurrence of the "Erosion of Hard Metal Coatings," LBL-15293. oxiaus and sulfides on each alloy was explained reasonably well, using tie appropriate thermo 5. E. Slamovich and A. Levy, "Erosion-Corrosion dynamic equilibrium stabi ity diagrams. of Steels in a Burner Duct Test Device," LBL-15657. Test; were performed on alloys containing 0-25rt Cr to determine the nature of the corrosion 6. A. Levy, P. Tom, and P. Yau, "Erosion Mecha problem in above-ground retorts that were retort nism of Steels in Liquid Slurries," LBL-15658. ing Green River shale where the operating temper atures are typically 50O-550°C« Only the 1018 7. A. Levy and E. Slamovich, "Erosion of Metals plain carbon steel showed mild corrosion (20 mil/ in Oil Shale Retorts—Final Report," LBL-13809. year) after 400 hours of exposure. These results indicate that there will be little or no corro Invited Talks sion problem in such retorts as long as tempera tures remain in the 500 - 550*C range. 1. A. Levy, "Erosion-Corrosion Behavior of Mater ials in Synthetic Fuels Processes," ASME Energy * * * Technology Conference, New Orleans, Louisiana, March 1982. l"8rief version of LBL-13809. 2- A. Levy and J. Patterson, "Elevated Temperature Erosion of Ductile Alloys in Neutral 1982 PUBLICATIONS AND REPORTS Gases," AIME-TMS Meeting, St. Louis, Missouri, October 1982, Other Publications 3. A. Levy and P. Tom, "Mechanism of Erosion of 1. A. Levy, "Metal Corrosion in Oil Shale Steels in Non-Aqueous Liquid Slurries," AIME-TMS Retorts," Proceedings of Conference on Corrosion- Meeting, St. Louis, Missouri, October 1982. Erosion-Vlear of Materials in Emerging Energy Systems, NACE, Berkeley, California, January 1982. 4. A. Levy, "Slurry Erosion of Alloy Steels at Elevated Temperatures," AIME-TMS Meeting, St. 2, A. Levy, "Erosion of Ductile and Brittle Louis, Missouri, October 1982. Materials," Proceedings of Conference on Corrosion-Erosion-Wear of Materials in Emerging 5. A. Levy, "Erosion Testing Using a Jet Nozzle Energy Sy^'^ems, NACE, Berkeley, California, Test Device," ASTM G2 Workshop, Williamsburg, January 1982. Virginia, December 1982. 217

c. Chemistry and Morphology of Coal Liquefaction*

Heinz Heinemann, Investigator, with Alexis T. Bell, James W. Evans, Richard H. Fish, Alan V. Levy, Eugene E. Petersen, Gabor A. Sormorjai, Theodore Vermeulen, and K. Peter Voilhardt, investigators

Introduction. This program is concerned with ied in a well-stirred autoclave. The product a basic understanding of the chemistry and physics distribution changes with time and approaches a of coal liquefaction and with coal gasification Schulz-Flory distribution asymptotically. Each as a preliminary step to liquefaction. It has product approaches the steady-state distribution brought together a team of organic, physical, and with a time constant that depends on the molecu organometallic chemists, chemical engineers, and lar weight and Henry's Law constant of the pro materials scientists, some of whom have had exten duct in the paraffin wax used to suspend the cat sive industrial experience. Accomplishments of alysts. A mathematical model of the evolution of the past year are presented in the reports of the the product distribution was found to describe six tasks involved. the observed results very successfully and to ex plain many anomalies in the published literature. Task 1-. SELECTIVE SYNTHESIS OF GASOLINE RANGE The dependence of the synthesis rates on Hg COMPONENTS FROM SYNTHESIS GAS+ and CO partial pressures, and temperature has been determined. The H2 dependence is unity A. T. Bell, Investigator with R. Dictor and for all products. The CO dependence is -0.42 J. Canella for methane and increases to zero for C4. This suggests that the formation of light hydrocarbons The research carried out during the past year can be reduced at low HJJ/CO ratios and high to has been aimed at three principal objectives. tal pressures. The activation energies for all The first was to develop a capability for com products were nearly the same, lying between 26 plete on-line analysis of the products produced and 29 kcal/mole. At low conversions the primary during Fischer-Tropsch synthesis. The second ob C2+ hydrocarbons are a-olefins, and the primary jective was to determine the influence of reac oxygenates are Cp+ aldehydes. As conversion tion conditions on the synthesis of hydrocarbons increases, the olefin to paraffin ratio decreases and oxygenated products over an iron catalyst con slightly, and the aldehydes are converted in tained in a well-stirred slurry. The third ob creasingly to alcohols. Very little methanol jective was to establish whether olefins, pro is produced at any conversion level. duced as a primary product of Fischer-Tropsch synthesis, undergo significant further chain growth and whether the recycle of olefins can be Experiments were conducted to test whether used to obtain non-Schulz-Flory product distribu the feedback of olefins could be used to alter tions. the product distribution. For these runs, a fixed bed reactor was operated at 305 *C and 5 atm, using a MvO/CO of 2 in the feed gas. Proper analysis of reaction products is es To simulate olefin feedback, 5% off ethylene, sential to understanding the effects of catalysis propylene, or cis-2-butene was added to the composition and reaction conditions on the kinet synthesis gas feed. It should be noted that ics of Fischer-Tropsch synthesis. For the pur the concentration of added olefin is much poses of the present task, a gas chromatographic greater than that pr'-sent due to synthesis system was developed that permits a complete on alone. The addition of ethylene causes a 60S line analysis of all products to be performed in increase in the production of propylene and no about an hour. A 1/8 in. x 9 ft stainless steel more than a 10% increase in the production of column packed with Chromsorb 106 is used to sep butenes. The balance of the product is unaf arate CO, COg, Ci through C5 hydrocarbons, fected by ethylene addition. The addition of as well as acetatdehyde and acetone; C4 through propylene causes a 15% increase in the forma C30 hydrocarbons and oxygenates are separated tion of butenes and a slight increase in the on a 50 m glass capillary column coated with 0V formation of ethylene, but has no other ef 101. The identity of the major and many of the fect. The only effects of cis-2-butene addition minor products have been established by GC/MS. are a 40% increase in propylene formation and a slight increase in ethylene formation. In each The synthesis of hydrocarbons over a fused Fe of the cases examined, the proportion of the catalyst, promoted with potassium, has been stud- added olefin converted to products of greater chain length is only a few percent. From these results, it is concluded that small olefins do *This work was jointly supported by the Director, not enter into the chain growth process very ef Office of Energy Research, Office of Basic Energy ficiently, and in fact may undergo hydrogenolysis Sciences, Chemical Sciences Division and the to produce lower molecular weight products. Assistant Secretary for Fossil Energy, Office of Coal Research, Liquefaction Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098 through the University Contracts Management Division of the Pittsburgh Energy Technology Center, Pittsburgh, Pennsylvania. tpartially covered by LBL-14964. 218

Task 2: ELECTRON MICROSl/)PE STUDIES*

0. W. Evans, Investi 'ator, nrith D. J. Coates

Controlled atmosphere electron microscopy (CAEM) has been used to examine high density pyrolytic graphite during the course of reaction with water vapor in argon, catalyzed by potassium and sodium hydroxide. Thin specimens of highly oriented pyrolytic graphite were mounted on grids and dipped into 0.38 M potassium hydroxide solu tion. After drying, the specimens were mounted on a heating 'jtage and placed into a Gatan "en vironmental cell" within a Hitachi 650 keV trans mission electron microscope. Argon, at approxi mately 1 attn pressure was bubbled through water at room temperature, giving an Ar/HgO ratio of about 40/1, and then introduced into the environ mental cell to give a pressure of 50 Torr. The specimens were heated in the flowing gas mixture and periodically observed. At 500*C the potass ium hydroxide was dispersed as particles 0.1 0.5 jjm in diameter on the surface of the graphite. With increasing exposure time, gasification was evident as the particles at the edges of the graphite crystals began moving toward the crys tal centers leaving channels in their wake.

Figure 2.1 shows two micrographs recorded 11 min apart taken from a sequence showing the chan nel growth at 500°C. Channels are evident in two adjacent graphite crystals emanating from the edges of the crystals, each channel with a parti cle at its head. The interface between the par ticles in the channels and the graphite shows a hexagonal, faceted morphology. As the reaction continues the particles move and the length of the channels increase, as can be seen by the par ticles arrowed. The channels remain roughly par allel-sided, indicating that there is little ef Fig. 2.1. {XBB 824-3397) fect of uncatalyzed reaction at the channel edges or of wetting of the channel sides by catalytic material. Initially particles lying on the sur face of the graphite crystals do not contribute to the catalytic gasification of the carbon. At a later stage, however, faceted pits in the graph ite are evident at the former positions of these Task 3: CATALYZED LOW TEMPERATURE HYDROGENATION particles. The catalyst particles are present OF C0ALT within, and at one edge of, the pits. In some cases channeling by these particles away from G. A. Samorjai, Investigator, with A. Cabrera and the original pits is evident. R. Casanova

The purpose of these studies is to produce Similar observations have been noted at 600*C. high molecular weight hydrocarbons by the catal At this temperature, however, no "incubation" per yzed depolymerization and hydrogenation of car was noted for the catalytic reaction involv iod bonaceous solids (graphite, char, etc.). ing the particles dispersed on the surfaces of the graphit: crystals and widespread channeling due to gasification was observed from outset. a. Methane Production From the Alkali Hydroxide These studies show that potassium hydroxide is Catalyzed Reaction of Graphite with Water Vapor effective in catalyzing the steam gasification of at Low Temperatures (50Q-600~KT graphite and that the mode of the catalyzed at tack is a channeling one with each channel being A. Cabrera headed by a particle of potassium compound. Sim ilar observations of the catalysis by sodium and The production of gaseous CH4 and CO2 (or calcium compounds have been made in the Berkeley CH4 and CO) from graphite occurs rapidly in the microscope. temperature range 500-650 K with low activation energy (10 * 3 kcal) in the presence of alkali * * * compounds. KOH, K2CO3, LiOH, CsOH, and NaOH all ^Partially covered by LBL-14463; Journal of Cat appear to catalyze both the reduction of C to CH4 alysis, in press. and its oxidation to CO? or CO. 219

b. Calcium Oxide Catalyzed Low Temperature hydrocarbons is obtained. However, the nature of Methane Production From Graphite the major products reported varied greatly in the early experiments, and the accuracy of the struc R. Casanova ture assignments might be held in doubt because of insufficient separation and characterization Calcium oxide catalyzes the transformation of of the product mixtures. A detailed analysis of graphitic carbon to an active form of carbon in the volatile components of the reaction has never the presence of water vapor: been performed.

CaO, H20 Heating benzene and A1C13 in a glass pres

(graphite) > r(dCtive). sure vessel under various conditions furnished alkybenzenes in addition to a variety of other This transformation could be monitored by x-ray products. Application of pressure, however, photoelectron spectroscopy, and its activation reduced the number of products (resulting in energy is 16.3 kcal/mole. Methane formation only cleaner GC traces) and their overall yield. occurs in the presence of hydrogen at the active carbon is gasified with an activation energy of A typical GC trace of the reaction of benzene 25.5 kcal/mole: with AICI3 shows the four major products being toluene, ethylbenzene, tetralin, and biphenyl. CaO + ^"(active) 2H2 > CH4. The reaction always yields some polymeric ma terials, believed to contain polyphenyls. The monitored reaction also shows an initial build c. Study of Potassium Intercalated Graphite up of polynuclear aromatic hydrocarbons such as methylphenanthrenes, methyl anthracenes, and Potassium-intercalated graphites CgK and C24K phenylnaphthalenes which are known to undergo have been employed for our reaction studies using Scholl-type polycondensation reactions in the water vapor. The rate of methane production is presence of A1C13. much lower for the intercalated samples than when KOH was on the external surface of the pure graph In order to minimize polymerization and con ite sample. It appears that alkali catalyst in densation reactions, several experiments were tercalation plays no important role during carried out under hydrogen in the presence of a gasification. catalytic amount of PtOj. Hydrogen consumption was fairly rapid, and as expected, the reaction was much cleaner. d. Reaction Rate Studies of the Structure Sensitivity of Graphite Gasification" Several labeling experiments were performed. Reaction of C6D5 gave completely labeled prod Reaction rate studies were carried out using ucts. Not unexpectedly, a 1:1 mixture of CQHQ different surface area and thickness graphite and D$0$ gave complete scrambling. Therefore, samples. While increasing the basal plane area an equimolar mixture of C.6H6 and 13C6Hg (90% en of graphite did not increase the reaction rate, riched) was exposed to AICI3 [Ng (1 atm), 160*C, increasing the thickness (edge area) increased 48 hr]. Surprisingly, 13C-I2C exchange (ca. 5%) the methane production rate in proportion. was observed in recovered "unreacted" benzene and additional scrambling in all other volatile prod * * * ucts as analyzed by GC/MS. The mass spectral peak patterns indicate substantially intact in Martially covered by LBL-15067. corporation of alkyl chains derived from the original benzene ring. Thus, the connectivity of the initial carbon arrays is extensively pre served in the alkybenzenes (including annulated Task 4: SELECTIVE HYOROGENATION, HYDROGENOLYSIS, and cycloalkylbenzenes) formed. The mechanism by AND ALKYLATION OF COAL AND COAL RELATED LIQUIDS which label exchange occurs is not understood at BY ORGANOMETALLIC SYSTEMS* present.

K. P. C. Vollhardt, Investigator An extension of our investigation involved the AlCl3-induced cracking of some cycloalkanes and a. Finalizing Studies on the Reaction of Benzene polynuclear aromatic hydrocarbons under hydrogen- with Aluminum Chloride ation conditions as models for the hydroliquefaction of coal and/or heavy petroleum hydrocar Y.-H. Lai and L. S. Benner bons. The results are summarized in the schemes below. In these reactions there was insubstantial The reaction of benzene with aluminum tri polymer formation, in contrast to the other stud chloride has been studied under many different ies. The reaction of larger cycloalkanes gives conditions, and generally a complex mixture of mainly ring contraction products. 220

Aid, Cr*0 a IQJ 160', 4.5 h -3S'A

Q0 • -HHIWIWI (^3_

0w5&r*wCr«Q -CT-OQ (CH,J

I60M2I. »•«-« «=HS>„ \ *-0-2

(-70% convtriion} -5%

n>4-6 o-oOO -11% -?% -9% -9»A -17%

It is clear that many of the reactions de proposal has prompted an investigation of the scribed will play a significant role in any thermal and photolytic chemistry of transition process that attempts to liquefy coal or heavy metal diene and triene complexes, models for the petroleum hydrocarbons in the presence of Lewis last two species in (1). acids. It appears that the use of Lewis acid alone leads to polymerization and subsequent We have found that CpCo-n^-cyclohexa-l,3-diene catalyst deactivation. On the other hand, sim (Cp = rfi-CsHtj) is remarkably stable thermally with ultaneous application of a platinum hydrogenation respect to ring opening, but that it undergoes catalyst and hydrogen> although successfully min relatively rapid intramolecular hydrogen shifts imizing polymerization, results in secondary re via intermediate metal hydrides. Moreover, on actions, such as premature hydrogenation competing laser irradiation one can observe the desired favorably with the cracking of hydrocarbons. A ring opening to CpCo-n^-l,3,5-hexatriene, successful method for hydroliquefaction of coal albeit with low quantum efficiency. would seem to depend on the search for a Afunc tional catalyst having complementary properties To probe the potentially adverse thermodynam of Lewis acid and hydrogenation activity. ics of the postulated ring opening, it was planned to test the thermal behavior of CpCo-n^-cis-1,3,5- hexatriene. For this purpose the complexation b. Diene Cobalt Complexes as Models for Hydro chemistry of the ligand under irradiative condi genous is of and Hydrogenshifts ij Coa1_|Unsatu tions was subjected to detailed scrutiny. A rates range of products was observed, including some of the desired cis-complex, but also a substantial We have postulated the theoretical feasibility amount of the trans-isomer. The latter is the of aromatic hydrocarbon hydrogenolysis by a route major compound on prolonged irradiation. We have involving an initial arene—dihydroarene step established the mechanism of this isomerization followed by a metal promoted ring opening to a through the investigation of labeled butadiene- complexed oligoene: CpCo.

Proposal (1) The reactions uncovered in this work consti tuted novel potential pathways by which hydrocar bons may transform on surfaces and in homogeneous catalytic hydrogenative and reforming systems. They also provide useful models for the possible chemistry of coal liquids when exposed to transi tion metal catalysts for the purposes of hydro & genation, desulfurization, and rearrangement.

If successful, this could provide a long sought and unique method for coal hydrogenolysis. This "•Brief version of LBL-15606, in press. 221

Task 5: CHEMISTRY OF COAL SOLUBILIZATION1 Task 6:. COAL CONVERSION CATALYSTS: DEACTIVATION 'STUDIES1, R. H. Fish and T. Vermeulen, Investigators, with A. D. Thormodsen A. V. Levy and E. E. Petersen, Investigators, with M. West and M. C. Smith We have demonstrated with model coal compounds, which include polynuclear aromatic and polynuclear Catalysts used to hydrodesulfurize coal-derived heteroaromatic nitrogen compounds, that transition liquids and petroleum residua are deactivated by metal carbonyl hydrides, generated catalytically the trace metals these liquids contain. The ti under a wide variety of conditions, selectively tanium in coal liquids and the vanadium in residua reduce the nitrogen heterocyclic ring in polynu deposit on the external and internal surfaces of clear heteroaromatic nitrogen compounds. More the catalyst, thus both blocking access to the over, we discovered that (foP^RhCl or Wilkin interior 01 the catalyst and covering active sur son's catalyst will also selectively reduce the face sites. Our objective is to examine this metal deposition process and how it affects de- nitrogen containing ring in polynuclear nitrogen sulfurlzation activity. We have approached the heterocyclic compounds under extremely mild con problem three different ways: we have measured ditions (80*C, 300 psi H2, for 2 hr). local metal deposition rates under realistic but experimentally manageable conditions; we have de With the latter catalyst (03P)3RhCl, we also veloped an extensive computer model describing found a dehydrogenation reaction with a saturated the deactivation of a single catalyst pellet by nitrogen heterocyclic compound, g-10-dihydrophen- metal deposits, and we have developed a technique anthridine, which provided the first example of a to measure directly the decreased diffusivity of transfer hydrogenation using quinoline as the ac a catalyst containing metal deposits. ceptor molecule.

The use of deuterium gas (Dg) in place of H2 A comprehensive set of experiments using has given important insights into the hydrogena vanadium naphthenates as a model compound and a tion reaction with phenanthridine and quinoline sour gas oil as a model liquid was completed dur as substrates. The position alpha to the nitrogen ing the past year. Stirred autoclave runs were in both dihydrophenanthridine (Co) and quinoline made from 325 to 400'C at vanadium levels of 100 (Cj) were deuterated. Additionally, exchange of to 400 ppm under 800 psig hydrogen and up to 48 an aromatic hydrogen for deuterium implicates cy- hr in length. Catalysts samples were withdrawn clometallation reactions in both cases (Schemes 1 periodically and analyzed for local metal con and 2). centration with KEVEX x-ray microanalyzer across a polished cross section. Radial concentration profiles of vanadium in catalysts samples taken at 8, 24, 32, and 48 hr are shorn in Fig. 6.1.

(al3P)3RhCI

500 psi D2 IOO°C for 3hr 10:1 substrate to metol ratio

(*3P)3RhCI

500 psi D2 m> 80°C for 48 hr

Initial competition experiments under hydro genation conditions revealed several interesting facts: Quinoline in the presence of thiophene, with (03P)3RhCl as catalyst, provided tetrahydro- quinoline with no apparent inhibition by thio phene. However, quinoline in the presence of pyridine was not hydrogenated implicating basicity as a criterion for reactions to occur. Possibly, pyridine acts, as CO did, by binding to rhodium and preventing quinoline from coordinat ing to the metal center. 10 20 PENETRATION,

••"Partially covered by LBL-13735. Fig. 6.1. (XBB 831-7572) 222

The temperature was 325"C and the vanadium con is evidenced by the vanadium-rich sludge that centration 200 ppm as naphthenate. Increased settles out of diluted gas oil samples. exposure time increases the airount of metal de posited and increased the eposit penetration. A model has been developed to simulate the These profiles are indicative of a diffusion- deactivation of a catalyst pellet during the controlled reaction. Deposition continues long desulfurization and demetallation of a heavy oil. after a monolayer of vanadium sulfide is depos The objective of the modeling is to examine the ited demonstrating that vanadium sulfide is resistance of different pore size distributions itself an active catalyst for demetallation. to deactivation so that catalyst improvements can be identified. Because of diffusion limitations, vanadium deposits preferentially at the outside of the cat The model is based on the solution of the dif alyst eventually building up a monolayer or more ferential equations for diffusion and reaction in of sulfide and covering the active molybdenum- a catalyst pellet. The main feature of the moJel cobalt sulfide surface. This layer of vanadium is the calculation of the model parameters from sulfide is still active toward demetallation so the pore size distribution of the catalyst as the deposition continues but at a slower rate than pore sizes are altered during the lifetime of the f.esh catalyst. catalyst.

Figure 6.2 shows smoothed radial concentration * * * profiles of vanadium from catalysts run at four different temperatures and otherwise similar con i"Brief version of LB1.-15432. ditions. As expected for a diffusion-controller1 reaction the apparent effectiveness factor de creases with increasing temperature, i.e., the profiles penetrate less deeply. However, the maximum demetallation rate at the outside edge 1982 PUBLICATIONS AND REPORTS where diffusion is not important decreases with increasing temperature instead of increasing as Refereed Journals crre^ted. The most plausible explanation for tfm phenomenon is that homogeneous demetallation 1. A. L. Cabrera, Heinz Heinemann, and 6. A. in the bulk liquid produces vanadium sulfide par Somorjai, "Methane Production from the Catalyzed ticles which reduces the concentratirn of vanadi- Reaction of Graphite and Water Vapor at Low Tem un naphthenate in the bulk solution, and the net peratures," J. Catalysis ^5, 7 (1982). result is a decreased overall demetallation rate on the catalyst. Homogeneous demetallation is 2. Richard H. Fish, A. D. Thormodsen, and 5. A. minimal at 325°C, but is extensive at 400°C and Cremer, "Homogeneous Catalytic Hydrogenation I," 0. Am, Chem, Soc. 104, 5234 (1982). LBL Reports

1. A. T. Bell and R. A. Pictor, »ftn Explanation for Deviation of Fischer-Tropsch Products from a Schulz-Flory Distribution;" submitted to I & EC Process Design and Development, LBL-14964.

2. R. Casanova, A. L. Cabrera, H. Heinemann, and G. A. Somorjai, "Calcium Oxide and Potassium Hydroxide Catalysed Low Temperature Methane Pro duction from Graphite and Water. Comparison of Catalytic Mechanisms," submitted to Fuel, LBL-15067.

3. Richard H. Fish and A. D. Thormodsen, "Selective Catalytic Reductions of Polynuciear Heteroaromatic Nitrogen Compounds, Using Both Homogeneous and Heterogenized Forms of Chorotris (Triphenylphosphine) Rhodium I," LBL-14958.

4. M. West, M. C. Smith, E. E. Petersen, A. V. Levy, and H. Heinemcin, "Hydrodeinetallation of Model Compounds of a Cobalt-Molybdenum Catalyst," LBL-15432,

Other Publication;

0 10 20 30 40 50 1. D. J. Coates, J. W. Evans, A. L. Cabrera, G. A. Somorjai, and Heinz Heinemann, "An Electron PENETRATION DEPTH. MM Microscopy Study of the Low Temperature Catalyzed Steam Gasification of Graphite," J. Catalysis, in Fig. 6.2. (XBB 831-7570) press. 223

2. V.-H. Lai, L. S. Benner, and K. P. C. 4. R. H. Fish, "Selective Catalytic Reductions Vollhardt, "Studies on the Reaction of Benzene of Polynuclear Heteroatomic Nitrogen Compounds," and Other Hydrocarbons with Aluminum Chloride. N. V. Academy of Science Conference on Catalytic The Effect of Catalytically Activated Hydrogen," Transition Metal Hydrides, New York, November Fuel, in press. 1982.

Invited Talks 5. K. P. C. Vollhardt, "Remarkable Bond-Making and Bond-Breaking in the Coordination Sphere of 1. Heinz Heinemann, "Alkali Catalyzed Low Temp Transition Metals," ACS Midland Section, Midland, erature Gasification of Graphite," Kurt Wohl Michigan, April 13, 19821. Memorial Lecture, University of Delaware, April 15, 1982. 6. K, P. C. Vollhardt, "Remarkable Rearrangements in the Coordination Sphere of Transition Metals," 2. Heinz Heinemann, "Heat and Mass Transfer University of Nice, Nice, France, June 1, 1982. Phenomena in Fischer-Tropsch Slurry Reactors," International Coal Conversion Conference, Pretor 7. K. P. C. Vollhardt, "Remarkable Rearrangements ia, South Africa, August 19S?. in the Coordination Sphere of Transition Metals," Indiana University, Bloomington, Indiana, October 3. Heinz Heinemann, "The Past 40 Years of Chemi 21, 1982. cal Industry," 5th Roermond Conference on Catal ysis, Roermond, Netherlands, July 1982. 224

d. Materials Characterization in Fossil Fuel Combustion Products*

Donald Boone and Alan V. Levy, Investigators

Introduction. The purpose of this study is to All of the coatings were brittle with a high ero develop an understanding of materials behavior in sion peak occurring at the start of each test with combustion zone environments by evaluating the a subsequent drop to a relatively low steady state behavior of specific material systems in engine erosion rate, which was much greater at 90* than tests and in appropriate laboratory simulations. at 30*. Coatings with a thickness <90 ym failed Development of a basic understanding of the cause almost immediately. Above a hardness of 3000 VHN, and effect relationship between material perform hardness did not affect the erosion rate. Below ance and the processing techniques used in their 3000 VHN the erosion rate increased significantly fabrication is an additional goal of this program. with decreased hardness. The CNTD SiC coating Particular interest has been focused on the diesel was superior to the standard CVD SiC coating, es engine and the combustion of lower grade fuels, pecially at 90* where the standard CVD SiC failed alternate fuels, and the direct combustion of immediately. coal. As a consequence, material performances have been determined by erosion, wear, hot cor The key to the erosion resistance of the CNTD rosion, oxidation and thermal fatigue resistance SiC is the extremely fine grain size deposited by testing. the continual renucleation of the grains as they are formed. The oriented, columnar growth of An additional aspect of this program has been standard CVD SiC is replaced with uniform, essen the correlation of national coating deposition tially equi-axed, extremely small grains in the research efforts, mainly in the area of high tem CNTD SiC, on the order of 1000 A or less (stand perature erosion resistant systems and ceramic ard CVD coating grain sizes can approach a mil11- thermal barrier systems, with laboratory and field meter diameter with large L/D ratios). The result testing both in diesel and gas turbine engines. is an erosion mechanism of very fine cracking and chipping of material around small surface craters. The lower erosion rates are due to the very small 1. EROSION OF SiC HARD COATING MATERIALS1- chips of material that are removed from the surface. Eric Scholz, Donald Boone, and Alan Levy * * * Silicon carbide is known to be an excellent combustion engine component protective coating "''Brief version of LBL-15293. because of its extreme hardness and very low wear rate and its resistance to high temperature cor rosion. In 1981 several of the most promising 2. EROSION OF CERAMIC THERMAL BARRIER COATINGS1" refractory hard metal coatings and monolithic bodies commercid'ny available or in development A. Davis, D. Boone, and A. Levy were erosion tested. A type of chemical vapor deposition (CVD) silicon carbide, called Con The use of ceramic thermal barrier coatings in trolled Nucleation Thermochemical Deposition a number of combustion engine types is often lim (CNTD) SiC, showed the best performance. This ited by their inadequate resistance to thermal year the CNTD SiC was examined more closely to fatigue, coating cracking, and spallation. Per determine the reasons for its superiority by formance has been significantly improved in these relating the erosion behavior to the properties areas by the introduction of controlled micro- and morphology of variations of the coating and porosity and/or microcracking in the ceramic to the effects of its manufacturing variables. structure, usually a stabilized or yttria partial ly stabilized zirconia. The purpose of this pro The variables considered were the hardness, ject was to determine the solid particle impact which is determined primarily by the level of free erosion resistance of the microporous and cracked silicon in the coating and coating thickness. coatings to determine their use potential in CNTD coating samples of five hardnesses, ranging engines burning degraded fuels. from 2400 to 4000 VHN, with thicknesses ranging from 80 to 210 urn were tested as well as a stand The erosion tests were carried out at room ard CVD SiC coating for comparison. The erosion temperature usinc, 60-100 um SiOg erodent parti testing was performed at room temperature using cles witt-. 30 m/s velocity at 90 and 30* impinge 200 urn SiC particles in a solid particle-airstream ment angles. Weight loss per unit of erodent was at 30 m/s at impingement angles of 30" and 90". measured, and the structures of the eroded sur faces were studied. Significant differences in erosion behavior were found between different ceramic coating structures, the processes used to *This work was supported by the Assistant produce them, and the compositions of the ceramic. Secretary for Fossil Energy, Office of Coal For plasma-spray-deposited ceramics, structures Research, Heat Engines and Heat Recovery Division with higher levels of microporosity and micro- of the U.S. Department of Energy under Contract cracking induced to provide acceptable thermal No. DE-AC03-76SF0009B through the Battelle Memor fatigue resistance exhibited reduced resistance ial Institute, Pacific Northwest Laboratories, to particulate erosion. However, a microstruc- Richland, Washington. turally segmented-ceramic structure aligned per- 225

pendicular to the substrate that was produced by Paper no. 128, ECS Annual Fall Meeting, Detroit, electron beam physical vapor deposition tech Michigan, October 1982- niques showed comparable erosion resistance to some of the more dense plasma spray coatings and LBL Reports better thermal fatigue behavior. 1. A. Davis, D. Boone, and A. Levy, "Erosion of * * * Ceramic Thermal Barrier Coatings," LBL-15667.

'''Brief version of LBL-15667. 2. A. Levy, T. Bakker, E. Sholz, and M. Aiabadeh, -Erosion of Hard Metal Coatings," LBL-15293. Invited Talks 1982 PUBLICATIONS AND REPORTS 1. 0. Boone, "Substrate and Processing Effects Other Publications on Carbon-Carbon Coating Systems,*' Composite Materials Conference, 6th Annual Conference of 1. E. Demeray, J. Fairbanks, and 0. Boone, the Ceramic-Metal Systems Division, American "Physical Vapor Deposition of Ceramic Coatings Ceramic Society, Cocoa Beach, Florida, January for Gas Turbine Engines,"Proceedings of the 1982 1982. ASME Gas Turbine Conference, Paper no. 82-GT-265, London, England, April 1982. 2. 0. Boone and J. Exell, "The Substrate HF Effect in Aluminide Coatings," AIME-TMS Fall 2. D. Boone, "Ceramics Coatings for Advanced Meeting, St. Louis, Missouri, October 1982. Energy Technologies," Proceedings of Ceramics in Advanced Energy Technologies Colloquium, The 3. 0. Boone and R. Lambertson, "The Effect of Petten Establishment, The Netherlands, September Aluminide Processing Variables on Oxide 1982. Structure, AIME-TMS Fall Meeting, St. Louis, Missouri, October 1982. 3. D. Boone, et al.,"The Structure and Perform ance of Electrophoretically Applied Aluminide 4. D. Boone and B. Rose, "Low Temperature Coatings," Proceedings of International Confer {700'C) Corrosion Testing of Modified Aluminide ence on Metallurgical Coatings, Thin Solid Films Coatings," AIME-TMS Fall Meeting, St. Louis, AVS, San Diego, California, April 1982. Missouri, October 1982.

4. D. Boone, M. Edwards, G. Newberry, "Low 5. D. Boone, R. Lambertson, and M. Barber, Temperature (704*C) Hot Corrosion of Hickel-Based "Protective Oxide Characterization of Mn Modified Superalloys, "Proceedings of Electrochemical Aluminide Coatings," AIME-TMS Fall Meeting, St. Society Conference on Corrosion/Energy Technology, Louis, Missouri, October 1982. 226

e. Solution Thermodynamics of Sulfites and Sulfite Oxidation Mechanisms*

Leo Brewor and Robert E. Connick, Investigators

Introduction. Acid rain is formed primarily ion. In some processes oxidation is desired and by the oxidation of sulfur dioxide to sulfuric in others avoided, so that control of the rate is aci.d when the former is released into the atmo of general importance. Study of the reaction is sphere through combustion of sulfur-containing difficult because it is a chain reaction and coal. Release of sulfur dioxide can be prevented therefore highly subject to catalysis and inhibi by passing the stack gases through aqueous scrub tion by a great variety of chemicals. Results bers of low acidity where the sulfur dioxide is are extremely difficult to reproduce. During the converted to bisulfite ion. The present project year attention was focused primarily on the detec is concerned with obtaining reliable thermodynamic tion of an intermediate in the reaction that has and kinetic data to support improvements in the been tentatively identified as a peroxy sulfite complex chemical processes that occur in flue gas species. Knowledge of its existence seriously desulfurization and to provide data for modeling limits the number of possible mechanisms that can these systems. be proposed for any given rate law. Present re search is being directed toward identifying the chain initiation step. 1. THE MEChANJSK OF OXIDATION BISULFITE ION BY OXYGEN

Robert £. Connicfc and Paul Chienq 1982 PUBLICATIONS AND REPORTS

Work in Progress. An important reaction in See section on "Formation of Oxyacids of Sulfur flue gas desutfurization processes is the oxida from SO2" for R. E. Connick and section on "High tion of bisulfite ion by oxygen to form sulfate Temperature Thermodynamics" for L. Brewer.

*This work was supported by the Assistant Secretary for Fossil Energy, Office of Coal Research, Advanced Environmental Control Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098 through the Morgantown Energy Technology Center, Morgantown, West Virginia. 227

(. Process Chemicals Parameters In Aqueous Sulfur Dioxide Removal by Lhne/Lfmestone Scrubbers*

C. Seat Meyer and Rob&rt E. Connick, Investigators

Introduction. In flue gas desulfurization processes for removing sulfur dioxide from stack * * * gases of coal burning power plants, the sulfur "fylork supported in part by the Department of dioxide is absorbed into an aqueous solution Chemistry, University of Washington, Seattle, where it may undergo a wide variety of reactions, Washington. depending on the particular process employed. *Brief version of Phosphorus and Sulfur 14, 23 The present work is aimed at investigating the (1982). ~~ basic chemistry of a number of species that can be formed in solutions under conditions similar to those in FGD processes. 2. THE STRUCTURE OF DITHIONITE ION1"*

1. THE THERMAL DECOMPOSITION OF AQUEOUS TRI- AND L. Peter§ and C. B. Meyer TETRATHIONATE+t Dithionite ion, S2042-, is a highly active and C. B. Meyer, M. Ospina, K. Koshlap, A. Tini, and widely used reducing agent whose structure in K. Ward solids and aqueous solution has been a matter of controversy. The x-ray investigation of Dunitz The polythionates constitute an important but showed the structure to be C2v ™ solid complex group of sulfur compounds formed in the ^SgO^HgO. On the other hand, Simor and acid decomposition of thiosulfate ion and in most Kuchler concluded from Raman spectra in solution systems containing any of the 13 oxyacids of sul that the ion was D2h* fur currently known. While a great deal of re search has been done on these species, the data Raman spectroscopy was used once again to in have been extremely difficult to interpret, vestigate the structure of the ion in solution. because there are usually a number of species Modern Raman equipment with lasers and photon present simultaneously and the analytical methods counting should yield more reliable results than are cumbersome and imprecise. It was hoped that the older apparatus that depended on photograph .c the application of modern techniques would lead recording. to a clearer understanding of their chemistry and therefore greater control of their effects in FGD The Raman spectrum of the aqueous ion differs processes. considerably from that of Na2S204-2H20. The spec trum found differed from the solution spectrum of Raman spectroscopy is an excellent tool for Simon and Ku'chler in that two additional weak detecting indivi_jal species since the Raman bands were detected and one reported by the earl l^nes of two species usually do not overlap, at ier authors could not be found. The spectrum was laast for all lines. Thus, it is usually possi compared to other X2Y4 type molecules and found ble to identify a particular species even in a to resemble that of P2F4 most closely. It is con mixture of several. The method suffers from lack cluded that the symmetry is C2h- It is al$o Pro of great sensitivity so that solutions of greater posed that the S-S bond length is considerably than ~0.03 M are needed unless resonance Raman shorter in the aqueous ion than in solid can be used. In addition it is not simple to get Na2S204*2H20 and that the configuration of the ion quantitative measurements of concentration, al is strongly susceptible to environmental effects. though this difficulty can be mostly avoided by using an internal standard. * * *

Raman studies have been made of the rate of "fWork supported in part by the Department of decomposition of 0.25 M trithionate and 0.5 M Chemistry, University of Washington, Seattle, tetrathionate ions at 20, 35, 50 and 70°C. Dur Washington. ing the reactions tri- and tetrathionate inter- tBrief version of J. Molec. Struc. j)5_, 131 (1982). convert. Thiosulfate is a prominent intermediate. §Present address: Chemistry Department, Seattle The end products are elemental sulfur, sulfate, Pacific University, Seattle, Washington 98119. disulfite, and bisulfite. The decomposition of trithionate initially follows a first order rate 1982 PUBLICAiTQNS AND REPORTS law with a rate constant of 0.14 hr-1 at 70*C. In the case of tetrathionate the reaction is pre Refereed Journals ceded by an induction period. 1. B. Meyer and M. Ospina, "Raman Spectrometric Study of the Thermal Decomposition of Aqueous Tri- and Tetrathionate," Phosphorus and Sulfur 1£, 23 (1982). *This work was supported by the Assistant Secre tary for Fossil Energy, Office of Coal Research, 2. L. Peter and B. Meyer, "The Structure of Advanced Environmental Control Division of the Dithionite Ion,1' J. Molec. Struct. 95, 131 (1982). U. S. Department of Energy under Contract No. DE-ACO3-76SF0O098 through the Morgantown Energy For publications by R. E, Connick, see section Technology Center, Morgantown, West Virginia. on "Formation of Oxyacids of Sulfur from S02-" Advanced Isotope Separation Technology 229

Advanced Isotope Separation Technology

A. Applications and Assessments of Advanced Techniques

a. Isotope Separation by Laser Photochemistry* C. Bradley Moore, Investigator

1. DETERMINATION OF ARRHENIUS PARAMETERS FOR 57.4 kcal/mol and log A(s-l) = 13.8 was used as UNIMOLECULAR REACTIONS OF CHLOROALKANES BY IR an internal temperature standard. For the molec 1 LASER PYROLYSIS ' ular elimination CCI3CH3 » HC1 + CCI2CH2, Ea = 49.5 ± 1.3 kcal/mol and log AJs"1) = 13.1 * 0.3 Hai-Lung Dai, Eliot Specht, Michael R. Berman, were determined. In these experiments the major and C. Bradley Moore* decomposition products of CHCI2CH2CI are HC1 and

cis- or trans-CHClCHCl with Ea « 58.5 * 2, log

In photochemical isotope separation schemes an A = 14.r±~074 and F.a = 59.5 * 2, log A = accurate knowledge of unimolecular reaction energy 13.9 ± 0.4, respectively (Fig. 1.2 and Table 1.1). barriers and rate constants is often required for modeling an enrichment process. Reaction rates as a function of total photon energy absorbed by a molecule and thermal reaction rates in ambient and laser-heated gasas must be known. Traditional methods measure rates on longer timescales than appropriate for most laser enrichment (LIS) pro cesses. Many literature data are in error due to unsuspected reactions on vessel walls or free radical chain reactions.

A simple and reliable method is elaborated for accurate measurements of thermal rate constants of homogeneous gas phase unimolecular reactions. A pulse of COg laser radiation was used to multiphoton excite SiF4 sensitizer molecules and consequently produce temperatures in the range 1100-1400 K. Expansion of the heated gas column quenches pyrolysis reactions on a 10 ps timescale, Fig. 1.1. There are no hot surfaces to induce chemistry. HC1 elimination from CiHrCl, Ea =

0.0011 1 I I 1 I 1 1 O.I 0.2 0.5 I 2 5 10 20 50 Ethyl Chloride Dissociation Yield (%) Rodius [cm) Fig. 1.2. The product yield from 112-TCE Fig. 1.1. Calculated temperature and gas density dissociation vs EtCl dissociation yield. Blank profiles at times following absorption of 0.044 0 points (0) are results from pyrolyses with the laser energy at 5.6 torr. The initial centerline 3.8-cm-long cell. Filled points (4) denote the temperature is 1334 K. (XBL 831-7981) pyrolyses without ethyl chloride, (s) denotes the short (0.9 cm) cell pyrolyses at the same pressure and (t) the pyrolysis with toluene in *This v/ork was supported by the Assistant Secretary the mixture. The curves are the best fits from the gas dynamic model calculation with E and A for Nuclear Energy, Office of Advanced Systems and a shown in Table 1.1 (for CCI9CH2, E = 27 kcal/mole Nuclear Projects, Advanced Isotope Separation Tech a nology Division of the U.S. Department of Energy and log A = 6.9 since most 1,1-dichloroethene is under Contract No. DE-AC03-76SF00098. formed by radical chain reaction. (XBL 831-7980) 230

Table 1.1. Rate Constants for Unimolecular Decomposition of CHCI2CH2CI.

E, (kcal/rrale), logTAts"1)]

Temperature a a a b Range cU-C2H2Cl2 trans-C2H2Cl2 CCl?CH2 CHClCH2Cl (K)

Sensitized 58.5 ± 2 59.5 * 2 >60 64 M Laser 1150 - 1400 Pyrolysis 14.1 * 0.4 13.9 * 0.4 <13.2 12.8 ± O.i

Chemical 59 - 60 59 - 60 57 -90 kcal/molec Activation

Flow 38 620 - 770 Pyrolysis 9.7d

Flow 34 640 - 800 Pyrolysis 9.9d

aValues are for the HCl molecular elimination reaction.

bDetermined from the yield of vinyl chloride.

cInitial energy constant.

dDetermined from the total HCl production rate. CCI2CH2 was the major product and is primarily derived from radical chain reaction.

HCl elimination to give CCI2CH2 and C - CI bond 1982 PUBLICATIONS ANO REPORTS breaking to CHCICH2CI radical have higher activa tion energies. The method is generally useful for Refereed Journals kinetics at high temperature, and especially use ful for LIS conditions. 1. H.-L. Dai, E. Specht, M. R. Berman, and C. Bradley Moore, "Determination of Arrhenius Parameters for Unimolecular Reactions of Chloro- alkanes by IR Laser Pyrolysis," J. Chem. Phys. *Brief version of LBU15665; J. Chem. Phys. 77, 27, 4494 (1982); LBL-15665. 4494 (1982). 'Joint Institute for Laboratory Astrophysics Invited Talks Visiting Fellow. 1. C. Bradley Moore, "Laser Isotope Separation and Photochemistry," Colorado School of Mines, Physics Department, Golden, Colorado, March 2, 1982.

231 Energy Storage

Electrochemical Energy Storage* James W. Evans, Rolf H. Muiler, John Newman, Philip N, Ross, and Charles W. Tobias, Investigators

Introduction. The overall aim of this program electrochemical processes employed in the conver is to improve the energy efficiency, lower the sion and storage of energy in electrolytic and capital cost, and increase the materials yielIdd of galvanic cells.

a. Surface Morphology of Mefals in Efectrodeposition*

Charles W. Tobias, Investigator

Introduction. The objective of this project rates were used in obtaining the cathodic polari is to develop a pragmatic understanding of the zation curves. High sweep rates (100, 200 mV/s) partial processes governing the macrocrystal1iza- and low concentrations (0.05 M, 0.10 M) of zinc tion of metals. This understanding is necessary in well-supported electrolyte solutions give dis for the design and optimization of metal deposi tinct limiting current plateaus for all rotation tion processes, including those in rechargeable al speeds (Fig. 1.1). In 0.05 M ZnCl2 + M KC1 galvanic cells. Current projects include: (1) solution, only the 200 mV/s sweep rate and the The effect of hydrodynamic flow on the surface lower rotational speeds (200, 400 rpm) give morphology of zinc, {2) dynamic modeling of sur limiting current plateaus. face profiles in electrodeposition and dissolu tion, and (3) mass transport effects in the Zinc diffusion coefficients obtained from the deposition of alloys. ...J- ... n ™ .. ,n_i 5 __?.2 . J- limiting currents are: 0.98 . lO".. cm-i/s in u,U0.035 rMi Lin.±2ZnCl2 + ' Mr> KCr\i*j1. anaudu u.0.7/ o8 r. 10—^ CID^/S i Ti 0.05 M ZnSo4 + M NajSO^ in reasonable agreement 1. LIMITING CURRENTS AND THE EFFECT OF HYDROOY- with literature values.1*2 The zinc surface NAMIC FLOW ON THE MORPHOLOGY OF ZINC DEPOSITS^ area increases too rapidly at slower potential sweep rates, and also at higher zinc concentra J. Faltemier, 0. Rajhenbah, and C. W. Tobias tion, to permit the development of distinct limiting current plateaus. The macromorphology of zinc obtained by electrodeposition from acidic zinr salt solutions is The morphology of electrodeposited zinc is studied under a wide range of process conditions investigated under galvanostatic conditions in a and electrolyte properties. The influences of channel flow cell with a ft cathode and Zn anodes, current density, pH, hydrodynamic conditionst in situ, using time-lapse motion picture photog time of deposition, and zinc salt composition are raphy. In the absence of mass-transfer control, investigated to evaluate the importance of each tine forms grooved deposits in a certain current one's contribution to the nature and quality of the deposit. Under certain conditions the mor phology of the deposit reflects the fluid motion over the surface of the electrode. Zinc has a tendency to form qrooved deposits in both laminar and turbulent flow and under conditions when mass- transfer is not controlling, i.e., well below the 1 iiii ting current.

To verify the transport conditions, mass transfer limiting currents of zinc deposition in acidic ZnCl2 and ZnS04 solutions have been determined by potential sweep voltammetry using a rotatinq disk electrode. Various zinc concentra tions, rotational speeds, and potential sweep

-2 05 E vs.SCE [V] *TM5 work was supported by the Assistant Secre tary for Conservation and Renewable Energy, Office Fig. 1.1. Cathodic polarization of Zn reduction of Enerny Systems Research, Energy Storage Divi ;n 0.05 M ZnCl2 + 1 H KC1 solution on a rotat sion of the U.S. Department or Energy under Con ing disk electrode at various rotational speeds. tract No. DE-AC03-76SF00098. Sweep rate 200 mV/s. (XBL 831-15) 232

density range (5-80 mA/cm2) reflecting the fluid For experimental verification of the model, a motion in both laminar and turbulent flow situa rotating-cylinder cell was designed and built. tions {Re 1600-9000); smooth deposits develop at The highly asymmetric electrode arrangement higher current densities, most likely because of promotes the coexistence of separate active and higher nucleation rates. Time-lapse motion pic passive regions on an anode that is segmented to ture experiments enable further study of the allow determination of currents by weight loss. sequence of events occurring in the development Typical results for the dissolution of a Ni 200 of zinc deposit morphology.3*4 anode in 2.0 M H2SO4 + 1.0 M NiS04 electrolyte are shown in Fig. 2.1. The location of the Within a few seconds after the start of Zn active-passive boundary was found to be stable, deposition, the Pt substrate is fully covered. and the character of the current distribution At low current densities (hence, low overpoten- followed expectations. tials) the deposit contains a large range of growing, protruding crystals. Because of ohmic The prediction from the model, using kinetic- advantage and also because of improved mass overpotential data and conductivities appropriate transfer, the large protrusions tend to grow to the experimental system, is shown and compared faster than smaller ones. Bttter mixing in the to the experimental cur.'ent distribution in Fig. wake of large protrusions tends to cause rapid 2.1. The agreement between experiment and theory nucleation anc formation of ridges. Eventually is good. the secondary t^ow patterns stabilize, resulting in the formation of well-defined, quite evenly spaced ridges in the metal deposit. At high cur rent densities the nucleation is more dense, the 1. G. A. Prentice, "Modeling of Changing Elec size distribution of crystallites is narrow, trode Profiles," Ph.D. thesis, LBL-11694. therefore protrusions, and hence striations do not form.

"•"Brief version of LBL-15338. 1. J. T. Kim and J. Jorne, JES, 127, 8 (1980). 2. J. Albright and D. Miller, J.~Solution Chem. £, 809 (1975). 3. T. Tsuda and C. W. Tobias, M.S. thesis by Tsuda, LBL-13056. 4. MMRD 1981 Annual Report, LBL-12838.

2. MODELING OF CURRENT DISTRIBUTION WITH ACTIVE-PASSIVE KINETICS

J. Dukovic and C. W. Tobias

Quantitative knowledge of the distribution of current is important to many electrochemical sys tems: batteries, electroplating, corrosion con trol, electroforming, etc. Numerical modeling has been successfully applied to a broad range of current-distribution problems, including systems with irregular and moving electrode profiles.*

The present work is designed to extend the scope of current distribution modeling to encom pass systems that involve active-passive kinetics. A case of special interest is the coexistence of distinct active and passive regions side by side on the same electrode. A finite-element model has been developed for celH that exhibit this phenomenon. As in previous models, the potential obeys Laplace's equation, but in this case the Fbsition relative to cathode (cm) boundary condition at the anodes comprises an Fig. 2.1. Current distribution as obtained by idealized active-passive, current-voltage charac experiment (horizontal dashes) and as predicted teristic. by the model (heavy line). (XBL 832-1187) 233

b. Metal Couples in Nonaqueous Electrolytes

Charles W. Tobias, investigator

Introduction. The objective of this project Table 1.1. Solubimies of Potassium Salts In Selected Organic Solvents. is to develop practical alternatives to aqueous or high temperature molten salt systems for the Molar Molal efficient electrochemical reduction and oxidation Salt Solvent Solubility Solubility Density 10 HO. of reactive metals. Past accomplishments include

development of a process for recovery of alkali 4 4 a KCl BL 7.49 X 10" 6.73 X lO" 1.1129 l

metals from their simple salts dissolved in -3 3 propylene carbonate solvent. Current work is DMF 1.99 X ID 2-12 X 10" 0.9386 2 -6 aimed at improving solvent preparation techniques, DHE 5.82 X 10 6.61 X 10"6 0.8813 3 increasing solvent stability, and identifying the EC 3.03 X 10"3 2.25 X 10"3 1.3498 4 a mechanisms by which co-solvents improve solubil PC 2.76 X 10~4 2.34 X 10"4 1.1817 5 ity and conductivity. A related project under the direction of R. H. Muller concerns the chemi

cal nature of surface films on alkali metals in 2 ? propylene carbonate electrolytes. QMF 6.52 X 10~ 6.90 X 10" 0.9476 7 DHE 2.56 X 10~4 2-90 X 10"4 0.8826 8a EC 3.11 X 10~2 2.31 X 10~2 1.3484 9 PC 4.81 X VO"3 4.04 X 10"3 1.1W6 10 1. SOLUBILITY OF POTASSIUM SALTS IN SELECTED ORGANIC SOLVENTS KI BL 0.755 0.641 1.2062 11 P. H. Johnson and C. W. Tobias OMF 1.66 1.51 1.1644 12 DHE 8.65 X 10"3 9.62 X 10"3 0.8824 13 Knowledge of the solubility of inorganic salts EC 0.891 0.630 1.4489 14 in organic solvents is needed to gain better un PC 0.251 0.225 1.2148 15* derstanding of solvation in organic media and to guide the development of organic electrolyte so KSCH BL 2.62 2.33 1.2283 16 lutions for electrochemical applications. In contrast to the relative abundance of data on DHF 1.87 1.96 1.0298 17 other properties of these solute-solvent systems DHE 2.05 2.26 0.9904 18a (e.g., conductivity, heats of solution, transport EC 1.64 1.22 1.4055 19 numbers), there is a paucity of data on solubil PC l.M 1.32 1.2479 20 ity.

2 KC104 BL 0.103 9.23 X Kf 1.1201 21 The solubilities and solution densities of DMF 0.971 0.985 1.0247 22a

4 4 five potassium salts (KCl, KBr, KI, KSCN, KC104) DHE 8.86 X ID" 1.01 X 10" 0.8800 23 is under study in five aprotic organic solvents: EC 0.694 0.519 1.3646 24 ethylene carbonate, propylene carbonate, butyro- 2 lactone, dimethylformamide, dimethoxyethane, and PC 4.43 X 10" 3.73 X I0"' 1.1888 25 mixtures of these solvents (Table 1.1).

The solvents and salts used were commercially ^High experimental uncertainty i solubility value. BL = butyrolactone available, reagent-grade. Solvents were dried DMF = dimethylformamide with molecular sieves (Linde 4A), and the salts DME a dimethaxyethane stored under vacuum over PJO5. Saturated solu EC = ethylene carbonate tions were prepared by adding an excess of the PC = propylene carbonate dried salt to the dried solvents in a capped vial. The vials were stored in a dessicator for at least a week and briefly shaken daily. The^ethylene carbonate solutions were stored at 40*C. The other solutions were stored at room temperature (22-2

Charles IV. Tobias, Investigator

Introduction. Electrolytic gas evolution is device to resolve mass transfer events on a scale among the most common reactions in electrolysis of 100 v are the three types of rate changes ob and in advanced rechargeable batteries. This served at various distances from a disengaging project is directed toward the quantitative de bubble (Fig. 1.1). scription of partial processes involved in the nucleation, growth, coalescence, and the detach ment of gas bubbles. Of special interest are the effects of moving individual bubbles and of gas- electrolyte emulsions on ohmic cell resistance 1. Dennie Dees and Charles W. Tobias, "Studies and on mass transport of charger, and uncharged of Bubble Dynamics on a Mosaic Electrode," MMRD species to and from electrode surfaces. A 1981 Annual Report, LBL-13840. thorough understanding of the physical processes, 2. Dennis W. Dees and Charles W. Tobias, "A involved in the liberation and movement of gases Micro-Mosaic Electrode for the Study of Transport at electrodes and in the electrolyte , should lead Phenomena at Gas Evolving Surfaces," Extended to improved energy efficiency and lower capital Abstracts, 33rd Meeting of the International costs in process and device technology. Society of Electrochemistry, Lyon, France, September 5-10, 1982, p. 456-458.

1. STUDIES OF BUBBLE DYNAMICS WITH THE MOSAIC ELECTRODE AND AN IMPROVED DATA ACQUISITION SYSTEM 0.H D. Dees and C. W. Tobias At a gas evolving electrode, surface molecules are produced and diffuse into the electrolyte, forming a supersaturated layer near the electrode. Bubbles are then nucleated and grow through coa lescence and diffusion until they disengage from the surface and rise, causing a microscopic flow of electrolyte, thereby enhancing the transport of reacting ions and product species. A micromosaic electrode capable of generating individual bubbles and measuring their effect on transport processes has been developed in this laboratory.*

The utility of the device to record changes in the rate of mass transfer during a single bubble disengagement has already been demonstrated.2 However, the micromosaic electrode has been found to be susceptible to mechanical degradation and chemical corrosion, despite the special protec tive safeguards designed into the device. The degradation of the electrode, which is quite BUBBLE ffEKHBC apparent from an examination with an optical I microscope, severely limits the useful lifetime of an electrode and makes it necessary to acquire IBB 181 IB? 1B3 the maximum amount of irformation from each ex TIHE (5EOJNDS) periment. To make this possible, a data acquisi tion system has been designed and built, and a program developed, in-house, for the on-line Fig. 1.1. Limiting currents for the reduction of control of tne mosaic electrode. The system is Fe3+ to Fe2+ to segments located at various capable of monitoring the current to each of the distances from a disengaging 1530-y-diam hydrogen segment? for a period of up to a few minutes and bubble. {XBL 833-89) can make as many as 100 current measurements to each segment per second. Faster or longer time studies car be made on fewer segments. The com 1982 PUBLICATIONS AND REPORTS puter not only controls the input/output of data, it also has the capability of monitoring and con Refereed Journals trolling the growth of bubbles during experiments. Data acquisition can be triggered manually or au tomatically by the computer. 1. C. W. Tobias and G. A. Prentice, "A Survey of Numerical Methods and Solutions for Current Dis tribution Problems," J. Electrochem. Soc. 129, 72 The micromosaic electrode coupled to the data (1982); LBL-12191. acquisition system was used to obtain more de tailed information2 on changes in mass transfer 2. C. W. Tobias and G. A. Prentice, "Simulation rates resulting from a single bubble disengage of Changing Electrode Profiles," 0. Electrochem. ment event* Indicative of the capability of this Soc. U9, 78 (1982); LBL-12192. 235

3. C. W. Tobias and G. A. Prentice, "Deposition 2. C. W. Tobias, Diamond Shamrock Lectures: •=nd Dissolution on Sinusoidal Electrodes," J. "A Perspective of Electrochemical Technology," £Iectrochem. Soc. ^29, 316 (1982); LBL-12167. January 25, 1982; "Current Distribution on Electrode Surfaces," January 27, 1982; "Mass 4. C. W. fo'oias ant G. A. Prentice, "Finite Transport in Electrochemical Cell Processes," Difference Calculation of Current Distributions January 29, 1982; "Physical Processes in Elec at Polarized Electrodes," AICHt. 28, 486 (1982); trolytic Gas Evolution,*' February 1, 1982, Case LBL-11058. ~~ Western University, Cleveland, Ohio.

+5. C. W. Tobias and P. C. Poller, :"The Anodic 3. C. W. Tobias, "Advances in Electrochemical Evolution of Ozone," J. Electrochem. Soc. 129, Technology," Seminar Lecture given at RCA Sarnoff 506 (1982). Research Center, Princeton, N. J., March 9, 1982.

'''6. C. W. Tobias and P, C. Foller, "The Mechanism 4. C. W. Tobias, "Assessment of the Future Po of the Disintegration of Lead Dioxide Anodes tential of Fuel Cells," Chevron Research Corp., under Conditions of n?one Evolution in Strong Richmond, CA, April 16, 1982. Acid Electrolytes," J. Electrochem. Soc. 129, 567 (1982). 5. C. W. Tobias, "Problems in Electrochemical Engineering," Seminar Lecture given at the Uni *7. C. W. Tobias, F. ". McLarnon, and R. H. versity of West Virginia, April 19, 1982. Muller, "Interferomemc Study of Combined Forced and Natural Convection," J. Electrochem. Soc. 129, *6. C. M. Tobias, R. H. Muller, and D. J. Roha, 2201 (1982); LBL-13032. "Effect of Suspended Particles on the Rate of Mass Transport to a Rotating Disk Electrode," The 48. C. W. Tobias and P. J. Sides, "Resistance of * 161st Meeting of the Electrochemical Society, a Planar l\rray of Spheres, Gas Bubbles on an Elec Montreal, Canada, May 14-19, 1982. trode," J. Electrochem. Soc. 129, 2715 (1982); LBl-13468. 7. C. W. Tobias and A. Kindler, "The Morphology of Eiectrodeposited Copper," The 161st Meeting of Other Publications the Electrochemical Society, Montreal, Canaoa, May 14-19, 1982. "!"1. C. W. Tobias and P. C. Poller, Inventors, "Electrolytic Process for the Production of 8- C. W. Tobias and Dennis Dees, "A Micro-Mosaic Ozone," U. S. Pattnt No. 4,316,782, February 23, Electrode for the Study of Transport Phenomena at 1982. Gas Evolving Electrodes," The 33rd Meeting of the International Society of Electrochemistry, Lyon, 2. C. W. Tobias, Chairman, "Assessment of France, September 6-10, 1982. Research Needs for • ivanced Battery Systems," Report of the CornmH.ee on Battery Materials 9. C. W. Tobias, "Fundamentals of Electrochemi Technology, National Materials Advisory Board, cal Engineering," Six lectures arranged by the Commission on Engineering and Technical Systems, Romande Intercantonal Association of Swiss Uni National Research Council, Publication NMAB-390, versities, Leysin, Switzerland, September 12-16, 1982. 1982.

3. C. W. Tobias and A. Kindler, "The Morphology 10. C. W. Tobias, "Prospects of Electrochemical of Eiectrodeposited Copper," Extended Abstracts, Technology,'" Seminar lecture, Swiss Federal In .he 161st Meeting of the Electrochemical Society, stitute of Technology, Lausanne, Switzerland, Montreal, Canada, May 9-14, 1982. September 22, 1982.

'4. C. W. Tobias, R. H. Muller, and D. J. Roha, 11. C. W. Tobias, "A Close Look at Electrolytic "Effe:t of Suspended Particles on the Rate of Gas Evolution," Seminar lecture, Stanford Uni Mass Transfer to a Rotating Disk Electrode," versity, February 24, 1982 and Ecole Nationale Extended Abstracts, The 161st Meeting of the Superieure des Industries Chimiques, Nancy, Electrochemical Society, Montreal, Canada, May France, October 11, 1982. 9-14, 1982.

5. C. w. Tobias and Dennis Dees, "A Micro-Mosaic 12. C. W. Tobias, "Perspectives on Electrochemi Electrode fur the Study of Transport Phenomena at cal Technology," Seminar lecture, De Guigne Tech Gas Evolving Surfaces," Extended Abstracts No. nical Center, Stauffer Chemical Co., Richmond, CA Il-C-19, Vol. I, p. 468, 33rd Meeting of the and Laboratoire d'Electrochimii Interfaciale du International Society of Electrochemistry, Lyon, C.N.R.S. Meudon (Bellevue) Fra.:e, October 14, France, September 10-15, 1982. 1982.

Invited Talks |Supported entirely from University funds. 1. C. W. Tobias, "Mass Transport and Current Supported by the Director, Office of Energy Distribution in the Electrodeposition of Metals," Research, Office of Basic Energy Sciences, IBM Corporation, GTIl Laboratory, Endicott, N. 0., Materials Sciences Division of the U.S.

January 2Zy 1982. Department of Energy. 236

d. Surface Layers on Battery Materials* Rolf H, Muller, Investigator

Introduction. The purpose of this work is to mediate film resistances. The protective proper provide direct experimental information about ties of these layers were still evident after formation and properties of surface layers on 250 h exposure to 1 H LiC104 at open circuit. battery electrode materials. Present studies are The formation of the nitride layer was found to concerned with lithium in nonaqueous solutions. be strongly inhibited by trace amounts of oxide. A more broadly based resaarch program, supported Ellipsometer measurements during polarization of by the Office of Basic Energy Sciences, Division lithium in 1 H LiClO/j/PC showed a large differ of Materials Sciences, DOE, is described in the ence between anodic and cathodic processes: sections "Electrochemical Phase Boundaries," metal dissolution appears to occur through the R. H. Muller, Investigator, and "Electrochemical oxide layer with roughening of the substrate, but Processes," C. VI. Tobias, Investigator. metal deposition occurs primarily on top of the oxide in the form of islands. * * * 1. IMPEDANCE AND ELLIPSOMETER MEASUREMENTS OF SURFACE LAYERS ON LITHIUM1" fBrief version of Extended Abstract, LBL-13618. 1. Y. Geroncv, F. Schwager, and R. H. Muller, J. Felix Schwager and Rolf H. Muller Electrochem. Soc. 129, 1422 (1982). 2. R. A. Huggins.TTectrochim. Acta 22, 773 Lithium is an attractive battery material (1976). ~ because of its high potential and low equivalent weight. Lithium can be used in different ambient- temperature nonaqueous electrolytes primarily 2. WORK IN PROGRESS because of the formation of surface iwjrs which prevent the spontaneous reaction of the metal Gholambbas Nazri and Rolf H. Muller with solvents and solutes. However, these sur face laye" hinder the efficient metal deposition Surface layers of improved ionic conductivity from solution during recharge. The present are necessary for the deposition of lithium from measurements were conducted in order to determine nonaqueous solutions in rechargeable batteries. film properties not affected by damage possibly To identify such surface layers, which also should inflicted in previous pulse measurements,! to be self-healing and inhibit corrosion reactions, investigate an approach to improve film conduc two approaches are being taken: control of com tivity, and to clarify discrepancies between ellipsometrically and electrochemically deter position and microstructure. To those ends, mined film thicknesses. Lithium nitride was improved means to form lithium nitride films and investigated as a protective surface layer be disordered oxygen and hydrogen-doped nitrides are cause of reported high ionic conductivity.2 under study. To further investigate the validity of the Simultaneous ac-impedance and ellipsometer conclusion^ that the protective surface layer measurements were conducted. Real and imaginary formed on lithium in propylene carbonate-lithitfn parts of the complex impedance were derived from perchlorate electrolyte was an oxide that resulted Lissajous figures of current and potential is- from reaction with residual water rather than played on an oscilloscope. The ellipsometer jas lithium carbonate, as conventionally accepted,2 of the self-compensating type in the polarizer- two experimental approaches are being taken: quarter wave plate-sample-analyzer configuration electrolyte of extremely low water content, pre with a mercury arc (546 nm) or argon ion laser pared by treatment with lithiun amalgam, is being (514 nm) light source. Nitride films were formed used, and freshly cut lithiur. electrodes are by different exposures to gaseous nitrogen. brought in contact with a i'ery small volume of electrolyte in a new thin-layer cell. Infrared Film resistances derived from the low-frequency spectroscopy has shown frig. 2.1) that the pre intercepts of complex impedance plots are in good cipitate formed on IHuium amalgam is not lithium agreement with pulse measurements. The previous carbonate but probably a polymerization product interpretation of differences in film thickness of the solvent. between optical and electrical measurements as being caused by inhomogeneous film structure therefore remains valid. The highest film resis 1. Y. Geronov, F. Schwager, and R. H. Muller, J. tance was obtained for films formed in LiClO^ Electrochem. Soc. ^29, 1422 (1982). solutions of propylene carbonate (PC), the lowest 2. F. P. Dousek, J. Jansta, and J. Riha, J. in pure solvent. Nitride layers showed inter- Electroanal. Chem. £6, 281 (1973).

*This work was supported by the Assistant Secretary for Conservation and Renewable Energy, Office of Energy Systems Research, Energy Storage Division of the U. 5. Department of Energy under Contract No. DE-ACO3-76SFO0098. 237

1982 PUBLICATIONS AND REPORTS

Refereed Journals

1. Y. Geronov, F. Schwager, and R. H. Muller, "Electrochemical Studies of the Film Formation on Lithium in Propylene Carbonate Solutions under Open-Circuit Conditions," J. Electrochem. Soc. 129, 1422 (1982); LBL-12102 Rev. 2.

Other Publications

1. F. J. Schwager and R. H. Muller, "Impedance Fig. 2.1. Infrared spectra of (A) Li2C03, and Ellipsometer Measurements of Lithium Elec (B) propylene carbonate, (C) liquid phase, and trodes in Propylene Carbonate Solutions," Extended (0) precipitate at lithium iimalgam-propylene car Abstract No. 295, Electrochemical Society, bonate interface. (XBL 831-7554) Detroit, Michigan, October 17-21, 1982; LBL-13618. 238

e. Electrode Kinetics and Electrocatalysis* Phillip N. Ross, Jr., investigator

Introduction. Complex electrochemical reac- single crystal substrates and the formation of tions in which chemical bonds are broken and/or platinum oxide on platinum single crystal sur formed are invariably catalytic, with electrode faces, both in acid fluoride electrolyte. The kinetics varying by many orders of magnitude for former is an example of an Me7Mez* electrode different electrode materials. Catalytic elec and the latter an Me/MeOx electrode. The plat trode materials are essential to technologies inum/platinum oxide system is of special funda like fuel cells, metal-air batteries, electrol- mental importance at present because of persistent yzers, and in electro-organic synthesis. Metal- speculation in the literature that cycling plat + metal ion (Me/Me2 ) couples form the largest inum electrodes through metal-oxide transformation class of negative electrode types for batteries. 2 z+ disorders the metallic state** and creates an Two general distinctions of Me/He couples can "activated'* state of platinum.3»4 be made: those where the ionic state (or dis charged state) is insoluble (e.g., a metal/metal oxide couple), and those where the ionic state is Figure 1.1a shows the LEED pattern for a UHV solvated (e.g., Zn/Zn2+ in acid). The kinetics prepared Pt(100) surface that was contacted with of Me/Mez couples ere relatively rapid, but are 0.3 M HF at 0.4 V RHE, swept ten times at 100 mV/s not usually controlled by only a charge transfer between 0.02 and 0.82 V RHE and separated from step. These reactions are often quasi-reversible, the electrolyte wMle potentiostated at 0.4 V. in the sense that they proceed at high rate and No significant differences were observed by LEED small overpotential, but they do not follow simple between this LEED pattern and the one for the charge transfer rate expressions. Phenomena fre surface exposed only to the argon backfill gas quently cited as contributing to the finite over- (at any incident beam energy 50-175 eVj. Expo potential in Me/Mez+ systems are critical nucle- sure of the UHV surface to the backfill gas ation, intermediate or precursor formation, and caused a transformation from the so-called (5 x impurity adsorption. In a mechanistic sense and ZQ) reconstructed surface to the (lOO)-(lxl) sur at the atomic level, several technologically im face structure. Thus, contact with electrolyte portant He/Me^+ systems are still not well un and potentiodynamic cycling within the metallic derstood. potential region causes no discernible changt in the structure of the surface.

Figure 1.1b shows the effect of cycling into 1. LOW ENERGY ELECTRON DIFFRACTION (LEED) CHAR the oxide formation potential region on the LEED ACTERIZATION OF METAL ELECTRODE SURFACES1" pattern at the beam energy of 134 eV. At 134 eV, the (10) and (20) spots were sharp while the (11) F. T. Wagner and P. N. Ross, Jr. spots are broadened. There was a characteristic alternate spot broadening as a function of energy, To understand what ho!>por>s at Me/Me^+ elec e.g., at 178 eV and 114 eV the (11) spots are trodes at the atomic level requires a method of sharp while the (10) and (20) were diffuse. The following the changes in the atomic structure of fact that every LEED beam is sharp at some energ the electrode surface. Low energy electron dif ies indicates that most surface atoms are still fraction (LEED) provides a sensitive probe of the in positions of the three-dimensional crystal atomic-scale structure of solid surfaces. Al lattice. Surface defects can introduce new peri though early LEED theory was restricted to the odicities with dimensions close to the incident treatment of perfect low index surfaces or sur electron wavelength to produce new spots or faces with perfectly ordered arrays of steps, the changes in spot shapes. The diffraction effects technique has been advanced to deal with a sta of periodic steps along the [010] and [Oil] di tistical distribution of steps and other forms of rections at a fee (100) crystal surface were com surface defects. Improvements in both theory and puted by the Ewald construction method. Given experimental technique are now allowing the type, diffraction data from a staircase stepped surface, size distribution, and density of imperfections one can determine the terrace width from the an to be identified. It should be possible to make gular splitting of the spots and the step height definitive structure determination of electrode from the incident energies at which the beams are surfaces by ex situ LEED analysis, thereby con sharp. If the steps are randomly up and down, siderably advancing the state of understanding the diffraction peaks become diffuse rather than the transformations occurring at electrode sur split at characteristic energies, but the mean faces. terrace width can be determined from the angular dispersion at the characteristic energies. Com parison of the Ewald construction with the energ Two electrode systems are currently under in ies at which the observed (11) and (10) LCED spots vestigation, zinc deposition on copper and gold were sharp are in exact agreement for randomly up and down monatomic steps, and from the analysis spot broadening the mean terrace width is calcu lated to be about 5 atoms or about 15 A. *This work was supported by the Assistant Secre tary for Conservation and Renewable Energy, Office of Energy Systems Research, Energy Storage It was concluded from the detailed analysis of Division of the U.S. Department of Energy under LEED patterns that a Pt(100) surface cycled 10 Contract No. DE-AC03-76SF00098. times through the surface oxide phase has a ver- 239 LEED 134 eV after ten cycles

a. to 0-82V(RHE) b. to 1-58 V (RHE) Fig. 1.1. (a) LEED pattern for Pt(100) cycled within me tallic potential region; (b) LEED pattern for cycling into surface oxide formation. (XBB 824-4022B) tically dislocated terrace structure with a mean tween two values, the more anodic of which is the terrace width of 15 A. The step dislocation den reaction equilibrium potential, calculated from sity is ca. 3 x 10^ sites/cm2 and the ordered the Nernst equation on the basis of c^, the (100) site density is 12 x 1014 sites/cm2, bulk concentration of the depositing ion. The i.e., about one atom in every four is associated Nernst-Siver approximation^ is used for the with a dislocation. A Pt(100) surface cycled Gnly RDE, whereas semi-infinite linear diffusion is within the metallic potential region has a longer assumed for the SPE. In both cases, capacitance range order, with a dislocation density less than and natural convection-effects are not taken into 5 x 10*3 sites/cm2, or only one atom in twenty consideration. is associated with a dislocation. Cycling through the oxide phase does introduce a significant con In the case of a RDE, a periodic [in the sense centration of high coordination sites into a low that the response to the (n + l)st sweep is in index surface, and would "activate" the surface distinguishable from that for the nth sweep] state for structure sensitive reactions. However, is obtained immediately after the first cathodic oxygen reduction is not a structure sensitive sweep, provided that the reversal time, ©, is reaction,5 and cycling the Pt(100) does not equal to or greater than the RDE characteristic "active" the surface for this reactior.. time 82/D (or 9' Ue/62 ___> 1), where 6 is the thickness of the Levich dTffusion layer. In terms of a dimensionless sweep rate,-? de- Brief version of LBL-15461. fined as 1. J. Clavilier, J. Electroanal. Chem. 107, 211 (1980). o = mFv62/RTD, v = dimensional sweet rate, 2. R. Parsons, 3. Electrochem. Soc. 127, 176C (1980). the periodic cathodic current maximum appears for 3. J. Hoare, Extended Abstracts Volume 82-1, The o*3 (Fig. 2.1). Compared to the linear sweep ilectrochem. Soc, Princeton, NJ, 1982, p. 571. voltammetry (LSV) maximum,2 it is lower in 4. A. J. Appleby, J. Electrochem. Soc. 117, 642 height and shifted in the cathodic direction. A (1970). net cathodic charge is obtained during each com 5. P. P.css, J. Electrochem. Soc., _126, 69 (1979). plete cycle indicating the formation of a net de posit on the electrode surface.

2. DIFFUSION CONTROLLED MULTI-SWEEP CYCLIC In the case of an SPE, it is shown that cur V0LTAMMETRY FOR A REVERSIBLE DEPOSITION REACTION rent transients (Fig. 2.2) are bounded from above OCCURRING ON ROTATING DISK AND STATIONARY ELEC by the LSV current and from below by the hypo TRODES" thetical periodic current obtained by reversing at infinite overpotential. Another hypothetical P. C. Andricacos and P. N. Ross, Jr. periodic state that is obtained by infinite cycl ing at finite reversal overpotentials follows the An analysis is presented of the behavior of a same rule. For the SPE, the true periodic state diffusion controlled reversible deposition reac requires either infinite reversal overpotential tion with constant deposit activity occurring on or infinite sweeps. For practical purposes, it rotating disk (RDE) or stationary planar (SPE) is more convenient to define a quasi-periodic electrodes. The potential is swept linearly be state. It was found that the higher the reversal 240

Fig. 2.?. SPE current density functions for dif Fig. 2.1. Periodic RDE current density functions ferent values of the number of already applied for o = 1,2, and 10. J = I/I'L, where i is the cycles and e reversal overpotential of 6RT/nF. 1 2 a current density during a potential sweep, and i|_ iM V(nFD / al/2cb)j where i is the current den is the RDE diffusion limiting current density. sity during the [z+ l)th sweep, and a = nFV/RT. J and J are current functions during cathodic c a The atc is overpotential in RT/nF units into a 2 and anodic sweeps, respectively. TC = Dtc/6 i$ cathodic sweep. Cathodic current maxima are dimensionless time itito a cathodic sweep. For bounded from above by the LSV transient,3 a<3, J ">sa monotonic function of T ; for higher c C ^°c max = 0.61, and from below by the periodic a values a maximum, J , appears in both LSV c max state at infinite reversal overpotential, and periodic current functions. For the LSV func 1 2 Ic,max = 0-19. (XBL 825-619) tion, J°c,max = 0.61a ' , a > 4 (Ref. 2), whereas for the periodic function, Jc max = - 0.88o0*25, o>9. |XBL 825-620) 1982 PUBLICATIONS AND REPORTS overpotential, the smaller the number of cycles Refereed Journals necessary to achieve quasi-periodicity. Multiple sweeping changes the linear dependence of the 1. F. T. Wagner and P. N. Ross, Jr., "LEED Anal cathodic current maximum on the square root of ysis of Electrode Surfaces: Structural Effects the sweep rate observed in LSV (Ref, 3) with gen of Potentiodynamic Cycling on Pt Single Crystals," erally smaller slopes that depend on the number J. Electroanal, Chem., in press (1982); LBL-14761. of cycles in addition to the usual parameters.3 Net cathodic charges are obtained after each com 2. P. N. Ross, Jr. and K. A. Gaugler, "The Ob plete cycle. servation of Surface Sensitive M;? 3 Absorption Edge Shifts by Reflected Electron'Energy Loss The theoretical expectations are being compared Spectroscopy (REELS); "Surf. Sci. to experimental observations for the electrodeposition of Ag from nitrate solution. Preliminary Other Publications results suggest excellent agreement with the pre dicted behavior. 1. A. J. Appleby and P. N. Ross, Jr., "Fuel Cell Systems for Electric Vehicles: An Overview," Power Sources for Electric Vehicles, edited by B. McNicol and D. Rand, Elsevier Scientific, 1982, TBrief version of LBL-14524 and L6L-14525. in press. 1. Yu. G. Siver, Russ. J. Phys. Chem. 33, 533 (1959); 34, 273 (1960). LBL Reports 2. P. C. Andricacos and H. Y. Cheh, J. Electro- chem. SDC. \Z]_, 2153 (1980). 1. P. N. Ross, Jr. and F, T. Wagner, "Prospects 3. T. Berzins and P. Delahay, J. Am. Chem. Soc. for the Development of Non-Noble Metal Catalysts 75, 555 (1953). for Hydrogen-air Fuel Cells," LBL-14192. 241

2. P. Adnricacos and P. N. Ross, Jr., "Diffusion on Pt Single Crystal Electrodes," 161st Meeting Controlled Multi-Sweep Cyclic Voltammetry: I. of the Electrochemical Society, Montreal, Canada, Reversible Deposition on a Rotating Disc Elec May 1982. trode," to be published in J. Electrochem. Sac, LBL-14524. 2. P. N. Ross, Jr., "Engineering Analysis of an NH3-Air Alkaline Fuel Cell System for Vehicles," 3. P. Andricacos and P. N. Ross., Jr., "Diffusion Workshop on Renewable Fuels and Advanced Power Controlled Multi-Sweep Cyclic Voltammetry: II. Sources for Transportation, Boulder, Colorado, Reversible Deposition on a Stationary Planar June 1982. Electrode," to be published in J. Electrochem. Soc, LBL-14525. 3. P. N. Ross, Jr., "Catalytic Properties of Pt-Group IV and V Intermetallic Compounds," 4. P. N. Ross, Jr., "Engineering Analysis of an Gordon Research Conference on Catalysis, New NH3~Air Alkaline Fuel Cell System for Vehicular London, New Hampshire, June 1982. Applications," LBL-14578. 4. P. N. Ross, Jr., "Structural Analysis of Electrode Surfaces by Low Energy Electron Dif Invited Talks fraction (LEED)," International Conference on Electronic and Molecular Structure of the Elec 1. P. N. Ross, Jr., "The Effect of Impurities trode-Electrolyte Interface, Logan, Utah, July and Potentiodynamic Cycling on Hydrogen Adsorption 1982. 242

f. Electrical and Electrochemical Behavior of Particulate Electrodes *

James W. Evans, Investigator

Introduction. .The purpose of this work is to electromagnetic forces. The model computes the investigate particulate electrodes in metal-air current distribution in the cell, the magnetic batteries. The acceptance of electric vehicles field, the electromagnetic stirring forces, the for public use depends on the development of a velocity field of the electrolyte and aluminum, high-efficiency* low-cost battery. The metal-air the bowing of the interface, and the current battery offers a prospect of meeting these efficiency. requirements if one or both of the electrodes are Figure 1.1 depicts the conductors in and around in the particulate form. Particle-to-particle six 185 kA cells forming part of two adjacent rows electronic conduction is essential for a particu of cells (three cells shown in each row). The late electrode to function and has a significant computed current efficiency for one of the cells effect on electrode performance; such conduction is also given in the figure. The computed inter is poorly understood, although there is evidence that conductivity decreases as the particle vol face shape for the cell shown arrowed in Fig. 1.1 ume fraction drops. This group's previous inves is depicted in Fig 1.2. The computed current tigation, mathematical modeling of aluminum efficiency and interface trough to peak distance reduction cells, was closed out late in the year are consistent with observations on actual cells. and is reported below.

1. DEVELOPMENT AND TESTING OF THE MATHEMATICAL MODEL FOR THE HALL-HEROULT CELL+

Steve Lympany,* Huai-Chuan Lee, and James W. Evans

The major consumer of energy in the production of aluminum is the Hall-Heroult cell wherein electrical energy is used to electrolytically r^, reduce aluminum oxide to metal. A mathematical model for the cell has been developed. Two per formance parameters of interest, from an energy 92.7% EFFICIENT consumption viewpoint, are the current efficiency of the cell and the flatness of the interface between the two liquid layers in the cell (molten Fig. 1.1. Six 18 kA quarter riser cells in two aluminum and the molten salt electrolyte). The potlines. Only the anode and cathode bus, risers, former variable has an obvious connection with and anode rods for each cell are shown. Subse the energy consumed per unit mass of product; the quent calculations are for the cell marked with an latter is important because "bowing" of this arrow and take account of the currents in all the interface prevents the reduction of the anode- conductors shown. (XBL 831-7977) interface distance (resistive losses in the electrolyte).

Both the current efficiency and flatness of the interface are primarily dependent on electro magnetic forces that arise within the cell from the interaction of cell currents with magnetic fields. The magnetic fields arise from current flow within the cell, surrounding conductors ("bus bars") and surrounding cells. The current efficiency is less than W0% because aluminum has a slight solubility in the electrolyte, and dis solved aluminum is transported to the anode where it reoxidizes. This transport of aluminum is because of turbulent convection in the electro lyte, and is, therefore, a function of the elec trolyte flow, a flow which is driven by the

TROUGH-PtAK DlSTANCh 3.8 CM.

Fig. 1.2. The interface between aluminum and *This work was supported by the Assistant cryolite computed for the cell indicated in Fig Secretary for Conservation and Renewable Energy, 1.1. Straight lines Indicate a horizontal plane. Office of Energy Systems Research, Energy Storage The vertical scale is exaggerated by a factor of Division of the U. S. Department of Energy under 40. Current flow in l.ht potline is from upper Contract No. DE-AC03-76SF00098. right to lower left. (XBL 831-7978) 243

During FY 1982 the mathematical model was used on a Hydrodesulfurisation Catalyst," Fuel 61, to predict the effect of design changes on cell 1245 (1982); LBL-13244. performance. It was predicted that separating the rows of cells by a greater distance would be 6. D. J. Coates, J. W. Evans, and K. H. beneficial, but that increasing the separation Westmacott, "Defects in Antiferromagnetic Nickel between cells in a row would have little effect. Oxide," J. Mat. Sci. .17, 3281 (1982). The model successfully predicted the well-known inferior performance of cells at the end of Other Publications rows. An interesting prediction was that the electrolyte/aluminum interface could be flattened 1. J. W. Evans, "Physical Chemistry of High considerably in a design in which current is re Temperature Technology," AIChE J. 28, 868 (1982), moved through the bottom of the cell, rather than book review. the sides (which is the present practice). Bowing of the interface is reduced by a factor of five for a ci.ll of this nature. vLBL Reports 1. S. D. Lympany and J. W. Evans, "The Hal 1- Details of the mathematical model and the Heroult Cell: Some Design Alternatives Examined computer programs have been requested by three by a Mathematical Model," Met. Trans, in press, aluminum companies (Alcoa, Reynolds, and Martin LBL-14386. Marietta) and have been transferred to them. 2. S. D. Lympany and i. W. Evans, "An Improved Mathematical Model for Melt Flow in Induction Furnaces and Comparison with Experimental Data," ^Brief version of LBL-14386, to be published in Met. Trans, in press, LBL-15170. Metallurgical Transactions. ^Present address: Dames & Moore, Golden, CO 3. D. J. Coates, A. L. Cabrera, J. W. Evans, 80401. H. Heinemann, and G. A. Somorjai, "An Electron Microscopy Study of the Low Temperature Catalysed Stear Gasification of Graphite," J. of Catalysis 2. WORK IN PROGRESS in press, LBL-14463.

The mathematical modeling of aluminum cells Invited Talks has been discontinued (at the request of DOE) in favor of an experimental investigation of the 1. D. J. Coates, K. H. Westmacott, and J. W. behavior of particulate electrodes. Such elec Evans, "The Effect of Microstructure on the trodes may find application in energy storage Reduction of Nickel Oxide," AIME Annual Meeting, (e.g., the zinc-air battery), but little is known Las Vegas, Nevada, February 1982. about their behavior. Of particular interest are conduction mechanisms within the electrode 2. M. Dubrovsky, J. W. Evans, and T. Huh, (particle-i.o-particle charge transport) and the "Fluidized Bed Electrowinning of Metals at transient behavior of the particle potertials. Moderate Electrical Energy Consumption Rates," An apparatus is under construction in which these AIME Annual Meeting, Las Vegas, Nevada, February two phenomena can be studied. 1982.

3. Y. Nakano, M. Abbasi, and J. W. Evans, "A New 1982 PUBLICATIONS AND REPORTS Predictive Technique for the Diffusion of Gases in Porous Solid," International Symposium on the Refereed Journals Physical Chemistrv of Iron and Steelmaking," Conference of Metallurgists, Toronto, Canada, i'l. I. Mastersoii and J. W. Evans, "Fluidized Bed August 1982. Electrowinning of Copper; Experiments Using 150 Amp and i,000 Amp Cells and Some Mathematical 4. S. D. Lympany, R. Moreau, and J. w1. Evans, Modelling," Met. Trans. ^3B, 3 (1982). "Magnetohydrodynamic Effects in Aluminum Reduc tion Cells," Proc. Int. Union of Theoretical and 12. M. Dubrovsky and J. W. Evans, "An Investiga Applied Mechanics Symp., Cambridge, England, tion of Fluidized Bed Electrowinning of Cobalt September 1982, Using 50 and 1,000 Amp Cells," Met. Trans. 138, 293 (1982). 5. S. D. Lympany, D. Ziegler, and J. W. Evans, "Simulation of Electrolyte Flows and Mass Trans- :>3. M. H. Abbasi and J. W. Evans, "Monte Carlo port in Electrometallurgy," AIChE Annual Meeting, Simulation of ftadiant Transport through an Adia- Los Angeles, November 1982. batic Parked Bed or Porous Solid," AIChE J. _28, 853 (1982). * * *

14. J. N. Barbier, P. Cremer, J. W. Evans, and ^Supaorted by the Office of Surface Mining, y. R. Fautrelle, "Simulation Numerique des Fours Department of the Interior. Chauffes par Induction," J. de Mecanique, ^Supported by National Science Foundation. Theorique et Appliquee _]_, 533 (1982). ^Supported by intramural funds, University of California. 5. D. J. Coates, J. W. Evans, and S. S. Pollack, ^Supported by the Institut de Mgcanique, "Identification of the Origin of Ti02 Deposits Grenoble, France. g. Electrochemical Properties of Solid Electrolytes* Lutgard C. De Jonghe, investigator

When sodium beta aluminas are in prolonged contact with molton sodium at elevated tempera tures, the sodium beta alumina is partially reduced.* xt\is leads to an electrolyte that contains a gradient in the electronic/ionic transport number ratio. Theoretical considera tions, based on thermodynamic calculations, in dicated that if current is passed through such an electrolyte, the possibility exists of internal deposition of sodium.2 Under normal circum stances, the cell operating conditions are such that internal sodium deposition does not occur. However, the presence of impurities may depress the applied voltage -J which such degradation may be initiated.

1. L. C. De Jonghe and A. Buechele, J. Mat. Sci. j7, 885 (1982). 2. L. C. De Jonghe, J. Electrochem. Soc. 129, 752 (1982).

1. IMPURITIES AND SOLID ELECTROLYTE FAILURE1* Lutgard C. De Jonghe A thermodynamically based model is used to assess the effects of the formation of a layer of lowered ionic conductivity and increased elec tronic conductivity on the applied voltage at which solid electrolyte failure is to be expected. Such a layer can result from electrolyte contam ination with electrode impurities. It is found that when a significant increase in electrolyte resistivity is produced, electrolyte failure can be initiated by deposition of sodium internally in the solid electrolyte. The results stress the necessity of operating solid electrolyte cells, such as Na/S, in a manner that minimizes elec trode contamination.

TBrief version of Solid State Ionics I, 61 (1982).

2. GRAIN BOUNDARIES AND SOLID ELECTROLYTE Fig. 2.1. (a) Optical micrograph of silver- 1 stained sodium exit surface for electrolyte DEGRADATION " subjected to unidirectional current flow of 50 mA/cm2, in a Na/Na cell, at 300aC. The two Lutgard C. De Jonghe, A. Buechele, and A. H. Yoon configurations of Mode I initiation have b^en labeled, (b) Lattice image of a grain boundary Sodium beta" alumina solid electrolytes structure corresponding to 1 in (a), (c) Lattice containing some very large grains were subjected image of a grain boundary structure corresponding to a unidirectional sodium ion current. The exit to 2 in (a). (XBB 823-2763A) surface of the sodium ions was then examined, and it was found that degradation has been initiated at the boundaries of very large grains (Fig. 2.1). The grain junctions are marked at 1 and 2. There is degradation at the junction of the two grains *This work was supported by the Assistant at 1, but none at the junction of the grains at Secretary for Conservation and Renewable Energy, 2; they are two different types of boundaries Office of Energy Systems Research, Electrochemical [Fig. 2.1(b) and (c/]. This observation suggests Systems Research Division of the U. S. Department that the long, faceted sides of the large grains of Energy under Contract No. DE-AC03-76SF00098. are mechanically weak. These facets correspond 245

to 00.1 planes. Further evidence of the low *4. L. C. De Jonghe and A. Buechele, "Chemical bonding strength along 00.1 faceted grain bound Coloration of Sodium Beta Aluminas," J. Mat. Sci. aries can be seen in Fig. 2.2, which shows a J7, 885 (1982). fracture along a partial 00.1 faceted grain boundary. In the region where the grain boundary ^5. L. C. De Jonghe, L. Feldman, and A. Buechele, deviated from an exact 00.1 facet, the spinel- "Failure Modes of Na-Beta Alumina," Solid State spinel block bonding, arrowed in Fig. 2.2, sur Ionics S 267 (1981). vived. The fractured path shows directly that t grain boundary strength depends on grain boundary structure. LBL Reports *1. L. C. De Jonghe, "Degradation Mechanisms of ''Brief version of LBL-14150. Sodium Seta Aluminas," L8L-14365.

+2. A. Buechele, L. C. De Jonghe, and D. Hitchcock, "Degradation of Sodium Beta" Alumina: Effect of Microstructure," LBL-13188.

T3. L. C. De Jonghe, A. Buechele,and K. H. Yoon, "Grain Boundaries and Solid Electrolyte Degrada tion," LBL-14150.

Invited Talks 1. Lutgard C. De Jonghe, "Solid State Electro chemistry and Batteries," Institute of Physics and Chemistry, University of Sao Paulo, Sao Carlos, Brazil, August 1982 (15 talks).

Fig. 2.2. Fracture at a grain boundary partially 2. Lutgard C. De Jonghe, "Materials Problems in faceted along 00.1 planes. Where the grain bound Energy Storage," Department of Materials Science, ary deviates from an exact 00.1 facet, as in Fig. Federal University of Sao Carlos, Brazil, August 2.1(c) direct spinel-spinel block rinds (arrowed) 1962. have survived. This demonstrates airect)y that the grain boundary strength depends on its 3. Lutgard C. De Jonghe, "Solid Electrolyte structure. (XBB 823-2134) Properties," Institute of Physics, Federal University of Minas Gerais, Belo Horizonte, Brazil, September 1982. 4. Lutgard C. De Jonghe, "Solid Electrolyte Batteries," Institute of Nuclear Energy Research, 1982 PUBLICATIONS AND REPORTS University of Sao Paulo, Sao Paulo, Brazil, September 1982. Refereed Journals 5. Lutgard C. De Jonghe, "Electrochemical Energy 1. L. C. Of1 Jonghe, "Impurities and Solid Storage," Energy Company of Sao Paulo (CESP), Sao Electrolyte Failure," Solid State Ionics 7, 61 Paulo, Brazil, September 1982. (1982). 6. Lutgard C. De Jonghe, "Microstructure and "2. L. C. De Jonqhe, "Transport Number Gradients Properties of Sodium beta Aluminas," RUCA, and Solid Electrolyte degradation," J. Electro- Antwerp, Belgium, June 1982. chem. Soc. V9, 75? (1982). 3. L. Feldman and L. C. De Jonghe, "Initiation of ynile I Degradation in Sodium-Beta Alumina '''Support was also provid-ad by the Electric Power Electrolytes," J. Mat. Sci. J7, 517 (1982). Research Institute. 246

h. Analysis and Simulation of Electrochemical Systems*

John Newman, Investigator

Introduction. This program includes the in Quantitative design and scale-up criteria are vestigation 6T efficient and economical methods needed for battery systems. Presently, paramet for electrical energy conversion and storage, and ric or empirical studies are done to determine development of mathematical models to predict the the effect of design variables on battery perfor behavior of electrochemical systems and to iden mance. A computer model that utilizes fundamen tify important process parameters. Experiments tal small cell data (or micromodeling data) is are used to verify the completeness and accuracy being developed that predicts the energy and pow of the models. er performance of a scaled-up battery. The model is general and may be applied to many types of battery systems. The battery can be optimized 1. WORK IN PROGRESS for maximum energy or power, or a compromise de sign may be selected. Inherent limitations of Experiments have been conducted to study the battery performance or specific areas of develop passivation behavior of iron electrodes in aqueous ment requiring attention can be identified. In acidic media. The experimental results obtained general, voltage and weight penalties of the cur with a rotating-disk electrode revealed an anodic rent collectors, interconnecting bus and post, limiting current. In an electrolytic solution of electrolyte, positive and negative active mater a given composition, the limiting current was ial, and cell container are taken into account. found to be proportional to the square root of Subject to variation or prediction are the number the di k rotation speed. For a given rotation of positive electrodes per cell, length of the speed, the limiting-current decreased with in bus and post, area of electrodes, current collec creasing electrolyte pH. Current oscillations tor weight, and total delivered capacity. These have been observed within certain potential results are based on a correlation of dimension- ranges on the limiting-current plateau. The fre less resistance vs plate area. This figure is quency of these oscillations has been found to be curve fit and is used to generate the combined proportional to the square root of the disk rota resistance of the electrochemical cell and cur tion speed. Subharmonic current oscillations rent collecting grids as a function of depth of have also been observed under certain voltage and discharge. Accuracy to within 3 to 5% of a more rotation speed conditions. sophisticated method is typically obtained.

Work is currently under way to develop a model An improved method for approximating the con describing the oscillatory phenomena. Physical ductivity of heterogeneous porous electrodes is phenomena judged to be important include iron being developed. The method currently used in dissolution kinetics, salt film formation and the mathematical model of the lithium-aluminum/ dissolution, potential distribution, concentra iron sulfide cell overestimates electrode conduc tion profiles in the electrolyte, hydrodynamics, tivity. An extension of the classical result of and the dependence of the passivation potential Maxwell was applied and resulted in effective on surface conditions. The model will include a conductivities as much as an order of magnitude stability analysis using techniques involving smaller than those obtained by the previous limit cycles and bifurcation analysis. method. This method will later be extended to develop a mathematical model of the lithium- An alternating current impedance method is be silicon/iron disulfide cell. ing used to study the anodic electrodissolution of a rotating zinc disk in an acidic chloride Channel flow between two plane parallel elec medium. Initially, the corrosion process must be trodes is used in many industrial electrochemical characterized by establishing the dc polarization processes, such as metal refining, energy storage, behavior. A model has been developed to analyze and electro-organic synthesis. A mathematical experimentally obtained kinetic data. The model model is being developed to predict the current also determines the corrosion potential and cur and potential distribution in a channel flow cell rent for a wide range of electrolyte compositions. with an interelectrode gap on the order of, or Finally, the ac behavior must be studied. An ac thinner than, the diffusion layer thickness. impedance experimental procedure, applicable over That is, a product from one electrode reaches and a wide frequency domain, is currently being de reacts at the other electrode. One of the pre veloped. Information about the capacitive double- liminary results of the model was a criterion to layer, along with the faradaic electron-transfer determine whether or not the thin-diffusion-layer reaction will be obtained and analyzed. approximation may be applied to a given channel flow cell. The model can take into account an arbitrary number of species and multiple reac tions at the electrodes.

An experimental research program is under way *This work was supported by the Assistant to develop a fundamental understanding of the Secretary f^r Conservation and Renewable Energy, precipitation of nickel hydroxide by the elec Office of Energy Systems Research, Energy Storage trochemical reduction of nitra*".? ions, which Division of the U.S. Department of Energy under changes the pH. This electrjdd recurs as the Contract No. DE-AC03-76SF00098. positive in a number of practical or promising 247

systems (those with negative electrodes of hydro 1982 PUBLICATIONS AND REPORTS gen, zinc, iron, and cadmium). Polarization characteristics of some nickel nitrate solutions Refereed Journals were determined with a rotating-disk-electrode apparatus. Ring/disk electrode experiments indi 1. Peter S. Fedkiw and John Newman, "Mass-Trans cate the irreversibility of the electrode proc fer Coefficients in Packed Beds at Very Low esses. Reynolds Numbers," Intern. J. Heat Mass Transfer 25, 935-943 (1982). The performance of sodium-sulfur secondary cells is strongly influenced by the diffusion of Invited Talks anions and cations through the polysulfide melt. Thus, optimal design of sulfur electrodes will 1. John Newman, "Electrochemical Systems Model depend upon the availability and accuracy of dif ing," Applied 8atter„ and Electrochemical Research fusion coefficient data for polysulfide melts. Program, Lawrence Berkeley Laboratory, Review of An experimental apparatus has been built to meas the Technology Base Research Project, June 2, ure the diffusion coefficient of sodium ions in 1982. melts of sodium polysulfides, using the method of restricted diffusion. Some preliminary experi 2. John Newman, "Mathematical Model of the ments have been performed with this apparatus, Li-Al/FeS Molten Salt Battery," Sandia National and work is currently under way to perfect the Laboratories, Albuquerque, New Mexico, Materials design of the apparatus. In addition, binary in Science Seminar, June 18, 1982. teraction parameters for sodium polysulfide melts, assuming a "pseudo-binary" melt, have been calcu lated using transport data obtained from the open 3. L. Redey, "Electrochemical Characterization literature. of Li-Al/FeS Cells," Detroit Meeting of the Elec trochemical Society, October 17-22, 1982. y/ 11 Magnetic Fusion Energy Magnetic Fusion Energy

a. Structural Materials and Weldmenls tor High Field Superconducting Magnets*

John W. Morris, Jr., Investigator

Introduction. Large, high field supercon ducting magnets are essential components in all current designs for fusion energy systems. The selection of suitable materials for the struc tures of these magnets poses unique problems. The magnet case must withstand the high struc tural loads imposed by the Lorentz force in the winding, and it sustains these loads at cryogenic temperature (4 K) in the presence of high mag netic fields. The effect of low temperature on the mechanical properties of structural alloys is only partly understood, and the influence of High magnetic fields is virtually unknown. The com bined requirements of high structural strength, high fracture toughness, and fatigue resistance in the superconducting magnet environment make it probable that new structural alloys will be needed for the construction of commercial fusion energy devices. The present project is intended to con tribute to the development of these new alloys by clarifying Use behavior of structural materials in the magnet environment and by designing, iden tifying, and testing new alloys and weldments that promise superior structural performance.

1. THE MAGNFTO-MECHANICAL CRYOGENIC RESEARCH FACILITY (MMCR)

B. Fultz, R. Kopa, and J. W. Morris, Jr.

Research on the mechanical properties of ma terials in an environment resembling that of a high field superconducting magnet requires a versatile facility capable of cryogenic tensile, fracture toughness, and fatigue crack growth mea surements in the presence of high, steady magnet ic fields. Standard fatigue and toughness tests require large specimens and therefore a large bore magnet.

Such a system has been installed in MMRD (Fig. 1.1}. The central element of the system is a large bore, NbTi superconducting solenoid that can achieve a field above 3.6 T. The test speci men is contained in a variable temperature anti- cryostat that has a cylindrical 101 mm diameter tail section within the solenoid. The cryostat Fig. 1.1. The MMCR facility. (CBB 824-4162) and magnet sit in a 244 kN Insuron 1332 servohy- draulic load frame with the actuator assembly mounted on its upper crosshead.

This device is capable of performing standard on full sized specimens at selected temperature laboratory tensile, toughness, and fatigue tests down to 4 K and magnetic field up to 8.6 T.

*This work was supported by the Director, Office of Energy Research, Office of Fusion Energy Development and Technology Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF0009R. 250

2. MAGNETIC FIELD EFFECTS ON MECHANICAL PROPER TIES OF STAHVLESS STEELS

B. Fultz, R. Kopa, G. M. Chang* and J. H. Morris. Jr.

The stainless steels that are now commonly specified for the structures of high field super conducting magnets are 304 and 316 in the L and LN grades. These steels are in an austenite phase that is metastable at cryogenic temperature. They undergo a martensitic transformation under strain that may be promoted by a high magnetic field. It is hence important to characterize their me chanical properties in the presence of high mag netic fields. It is expected that the largest field effect will appear in fatigue tests, but it is first necessary tn study tensile behavior.

Preliminary tensile tests have been conducted on both 304L and 304LN alloys in various process ing conditions. These tests reveal systematic changes in the tensile properties at 77 K in an 8 T field. The flow stress increases, the ultimate 0 I I ! I t I i L_ tensile strength increases, and the elongation 800 IOQO 1200 1400 drops. The effect increases with the amount of Yield Stress. MPa prior deformation on the sample. The increase in flow stress is approximately 8% in cold worked Fig. 3.1. The strength and toughness of three 304LN. Fe-Mn research alloys at 4 K are compared to the Lrend lint for conventional stainless steels and to the "JAERI envelope," the target values for magnet case materials for the Japanese fusion 3. AUSTENITIC Fe-Mn CRYOGENIC STEELS program. (XBL 824-5496)

R. Ogawa and J. W. Morris, Jr. 1982 PUBLICATIONS AND REPORTS Nonmagnetic steels from the Fe-Mn system are potential structural alloys for the cryogenic Other Publications cases of high field superconducting magnets. Alloys from this class offer excellent strength 1. J. W. Morris, Jr. and B. Fultz, "Effects of and toughness at 4 K, are nonmagnetic even under Magnetic Fields on Martensitic Transformations large strains, and are inexpensive relative to and Mechanical Properties in Stainless Steels at the conventional stainless steels. Low Temperature," Proceedings of the Internation- al Cryogenic Materials' Conference, Kobe, Japan, Recent research under this project1 concen ecTited by K. Tachikawa and A. Clark, Butterworths, trated on the role of the interstitial content in London, England, 1982, p. 343. cryogenic mechanical behavior of Fe-Mn-Ni-Cr al loys. This investigation led to the selection -jf 2. R. Ogawa and J. W. Morris, Jr., "The Influence the composition Fe-18Mn-5Ni-l6Cr-0.024C-0.22N. of Nitride and Carbonitride Precipitation on the This ' ioy was made and tested at 4 K. Both its Cryogenic Mechanical Properties of High Manganese strenyth-toughness combination and its fatigue Austenitic Steels," Proceedings of the Interna properties equal or exceed those of 304LN. Its tional Cryogenic Materials Conference, Kobe, strength-toughness characteristic is compared to Japan, edited by K. Tachikawa and A. Clark. the trend line for conventional stainless steels Butterworths, London, England, 1982, p. 124. in Fig. 3.1, Its properties exceed those of the stainless steels and approach the "JAERI enve LBL Reports lope," the target range of properties set by the Japanese fusion program. 1. H. 0. Kim and J. W. Morris, Jr., "The Devel opment of a Ferritic Consumable Welding Grain- * + * Refined Fe-12Ni-0.25Ti to Retain Toughness at 4.2 K," Welding J., in press, LBL-13046. 1. R. Ogawa and J. W. Morris, Jr., Proceedings of the International Cryogenic Materials Confer 2. B. Fultz, G. M. Chang, and J. w. Morris, Jr., ence, Kobe, Japan, edited by K. Tachikawa and A. "Effects of Magnetic Fields on Martensite Trans Clark, Buttei worths, London, England, 1982, p. formations and Mechanical Properties of Steels at 124. Low Temperatures," in press, LBL-15518.

Nuclear Waste Management

a. Thermodynamic Properties of Chemical Species In Nuclear Waste*

Norman M. Edelstein, Investigator

Introduction. The purpose of this program is to investigate the thermodynamic properties of anticipated actinide and fission product ions and the compounds they may form in geologic environ ments, so that their chemical behavior and poten tial migration in a nuclear waste setting can be assessed with improved capability.

A number of laboratory studies are being under taken to obtain data concerning species, oxidation states, effect of complexing ligands, and other related information. Such data will contribute to a better understanding of the chemical systems that may be involved in various geologic media and will furnish more reliable parameters for radio nuclide migration modeling studies.

8.33 in 0.05 M NaC104. (XBL 833-8701} The lack of accurate thermodynamic data for actinide species in aqueous solution prevents a realistic assessment of the amounts and rates cf Since there is no information available on the release of radionuclides from an underground formation constant for the 1:3 complex of waste repository.1»2 One of the more important actinide nuclides for which little accurate data Np02(C03)3 , we have used the value of log

is available is neptunium, which can exist in the S = 21,4 for the corres ndin U0 C0 +5 state under environmental conditions.^ 130 P° 9 ?( 3'3 (Ref. 6) and obtain the stability constant for

+ 3 We have studied the complexation of Np02 Np02(C03)2 " of log fi12Q = 11.2 ± 1. Verifica 5 (c = 5.9 x 10~ M) at a pH of 8.33 by carbonate ion tion of this result is under way by spectrophoto- in NaClOfl solutions (I = 0.05 M) by computer con trolled voltammetry.4 The data have been analyzed metric methods. by use of the Lingane equation.5 Figure 1.1 shows the differential pulse voltammograms of the quasi- reversible Np02+ oxidation with increasing car 1. J. M. Cleveland, in Chemical Modeling in bonate concentrations and the subsequent negative Aqueous Systems, edited by E. A. Jenne, ACS potential shift. Symposium Series 93, Washington, D.C., 1979, p. 16. From an analysis of this data and assuming the 2. B. Allard, "Solubilities of Actinides in most stable complex for the oxidized species is Neutral or Basic Solutions," in Proceedings the 1:3 complex NpOgtCO^4-, we find of the Actim'des-1981 Conference, edited by N. Edelstein, Pergamon Press, Oxford, 1982, p. 553. /0NpO (COj/-\ ? 3. .1. B. Moody, Technical Status Report,

e OWNI-321 (1981). \ Np02(C03)/ / 4. S. D. Brown and B. R. Kowalski, Anal. Chim. Acta .107, 13 (1979). 5. J. J. Lingane, Chem. Rev. 20, 1 (1941). 6. S. L. Phillips, LBL-14313,~T982.

*This work was supported by the Assistant Secretary of Nuclear Energy, Office of Commercial 2. THE SOLUBILITIES OF CRYSTALLINE NEOOYMIUM AND Nuclear Waste Management, Commercial Waste Manage AMERICIUM TRIHYDROXIDE ment Program Division of the U.S. Department of Energy under Contract No. OE-AC03-76SF00098 R. J. Silva through th? Battelle Memorial Institute, Office of Nuclear Waste Isolation (QNWI), Columbus, Ohio, One of the hazardous actinides in nuclear under MPO No. E511-05100. waste.from a long-term point of view is americium.* If trivalent Am behaves like the trivalent lanthanides, and there is good reason to expect that it will,2 Am would be expected to form an insoluble hydroxide under environmental conditions. Unfortunately, there has been no systematic investigation of the solubility of well-characterized Am(0H)3 reported in the lit erature. The objective of this work was: (1) to measure the solubility of well-characterized, crystalline Am{0H)3 as a function of pH and obtain a value for the solubility product con stant, and (2) to measure the solubility of well- characterized crystalline Nd(0H)3 as a function of pH and, by comparing the results with (1) above, determine if it is a good analog compound

for Am(0H)3.

Pure crystalline Nd{0H)3 and Am(0H)3 were prepared and characterized through the measure ment of their x-ray powder patterns. Portions of the solid materials were placed separately in contact with aqueous solutions of 0.1 M NaClO^ of different pH values at 25 ± 1*C. TKe solubil ities of the two materials were determined from measurements of the solution concentrations of Nd and Am as a function of time. The open points in Figs. 2.1 and 2.2 are the results of the experi mental measurements for Nd and Am, respectively. Fig. 2.2. Plot of the logarithm of the solution concentration of Am in aqueous 0.1 M^ NaC104 solu tions as a function of pH at 25°C. (XBL 8210-1201)

Nd (OH), The results of the experimental measurements were analyzed in terms of the solubility product and hydrolysis reactions given in Table 2.1. Also presented in Table 2,1 are the thermodynamic constants for the reactions for Nd given by Baes and Mesmer.3 Since the analysis involves the B \A solution of a number of coupled equations simul taneously, the calculations of the concentrations of solution species and solubilities from the thermodynamic constants were made using a com \ puter code called MINEQL.4 \ The solid curve labeled (A) in Fig. 2.1 \ resulted from calculations using the constants of Baes and Mesmer.3 Clearly, the predicted solu bility of Nd(0H)3 was considerably higher than that measured in these experiments. Analysis of the data involved syscematically varying the val ues of the constants for reactions (1), (3), (4), and (5), and comparing the resulting calculated curves with the experimental points in Figs. 2.1 and 2.2. The solid curve labeled (B) in Fig. 2.1 and the solid curve in Fig. 2.2 represent the best fits to the experimental data. The values of the solubility product and hydrolysis constants used pH to obtain the best fits are given in Table 2.1 Fig. 2.1. Plot of the logarithm of the solution for both Nd and Am. The solubilities and specia- concentration of Nd in aqueous 0.1 M_ NaC104 solu tion of Nd and Am as a function of pH are quite tions as a function of pH at 25"C. similar, and Nd(0H)3 sho-jld be a good analog (XBL 8210-1200; compound for Am(0H)3. 253

Table 2.1. Solubility Product and Hydrolysis Constants of tid^* and Am3+ for 25°C and Corrected to Zero Ionic Strength.

Log K Nd Am (Ref. 3) {This work) {This work)

+ + (1) M(0H)3(S) + 3H = M3 + 3H20; Ksl0 18.6 16.0 ± 0.2 15.9 ± 0.4

+ + + (2) M3 + H20 = M(0H)2 *• H ; Kn -8.0 -7.7 + 0.3 -7.7 * 0.3

+ + + + (3) M3 + 2H20 = M{0H)2 2H ; K12 -16.93 -15.8 ± 0.5 -15.0 * 0.7

+ + (4) M3 + 3H20 = M(0H)3° + 3H ; K13 -26.5^ -23.9 * 0.2 -24.3 ± 0.3

3+ + (5) M + 4H20 = M(0H)4- + 4H ; K14 -37.1 <34 <34.5

aPredictions.

controlled automatic titrator and the program STBLTY for data analysis.1 1. J. B. Moody, Radionuclide Migration/ Retardation: Research and Development Technology The hydrolysis and precipitation reactions for Status Report, Office of Nuclear Waste Isolation, the metal ions under study are given in Table 3.1 Battelle Memorial Institute report ONWI-321, along with the results of an earlier study? for 3+ 1982, p. 6. Np02 and the best values for Nd as determined 2. C. F. Baes, Jr., and R. E. Mesmer, The by Baes and Mesmer in their critical review.3 Hydrolysis of Cations, W.iley and Sons, N.Y., Our experimental values are also listed in Table + and lo 1976, p. 191. 3.1. For Np02 our value of log Kxo-l 9 3. Ibid, p. 137. Ksl0-1 confirm the results of the earlier study.2 4. J. C. Westall, J. C. Zachary, and F. M. M. The values found for the first hydrolysis quotient Morel, "MINEQL, A Computer Program for the Calcu of Nd3+ and Cm3+ are approximately the same and lation of Chemical Equilibrium Composition of agree well with the Ndj+ value chosen by Baes Aqueous Systems," Oept. Civil Eng., Massachusetts and Mesmer.3 We found no strong evidence for Institute of Technology, Cambridge, MA, Technical the formation of dimers or higher polymeric spe Note 18, 1976. cies; our data could equally well be explained by 5. N. Edelstein, J. Bucher, R. Silva, and colloid formation before the hydroxide precipi tates. Our value for the Nd(0H)3 solubility, H. Nitsche, "Thermodynamic Properties of Chemical K = Species in Nuclear Haste: Topical Report," log sl0-3 15.8, is in reasonable agreement 0NWI/LBL-14325. with the value for Cm(0H)3 solubility, but dis agrees by approximately three orders of magnitude

with the literature value, log Ksxo_3 = 18.6. It is, however, in excellent agreement with 3. HYDROLYSIS AND HYDROLYTIC PRECIPITATION recent measurements of the solubility of + + + REACTIONS FOR Np02 , Nd3 , and Cm3 Nd(0H)3 and Am(0H)3 determined by radiochemical techniques.^ Finally, it is important to note J. J. Bucher and N. Edelstein that tne hydrolytic behavior of Nd3+ and Cm3+ is similar as expected from the systematirs of the A number of long-lived actim'des are present chemistry of the trivalent ions of the lanthanide in spent nuclear fuels and high level processed and actinide series. waste in sufficient quantities to remain a radiological hazard, even after 1000 years, if placed in an underground repository. If these materials interact with groundwater, a number of insoluble compounds and solution species can be 1. A. Avdeff, and J. J. 8ucher, Anal. Chem. 50, formed. In order to determine what species can 2137 (1978). ~~ be formed with various anionic species, reliable 2. K. A. Kraus, and F. Nelson, U.S.A.E.C. Report thermodynamic data must be available for hydrol AECD-1864, 1948, Oak Ridge, TN. ysis reactions and for the solubilities of the 3. C. F. Baes, and R. E. Mesmer, The Hydrolysis metal hydroxides. We have studied these reac of Cations, Wiley-Interscience, N.Y., 1976, p. + tions for the univalent species Np02 and for 3+ 3+ two trivalent ions Cm and Nd , by u poten- 4. R. J. Silv-, Lawrence Berkeley Laboratory tiometric titration method using a computer- Report LBL-15055, 1982. 254

Table 3.J. Hydrolysis Quotients and Solubility Product of NpOj+, Nd3+ and Cm3+ in Approximately 0.1 M KCL.

Log Q

Reaction3 Literature This Work

b 1) Np02 + HOH = Np02(0H) + H ; Kj^j -8.85 -9.05 ± 0.05

4.81' 5.3 ± 0.1

J 12L + , -8.0C -7.7 ± 0.3 3) M + HOH = M(0H) ++ H'; K 10-1 4) 2M3+ + ZHOH = M (0H) 4+ + 2H+; K _ -13.8fic 2 >22 ?Q 2 -

c J lu <-28.5 ' 3 "'5 ' -"' ^30-5 -

+ + 6) M{0H)3 solid + 3H = M3 + 3H0H; Ksi0-3 18.6C 15.8 * 0.2

Ref. 2. For Nd3+ from Ref. 3.

1982 PUBLICATIONS AND REPORTS Neodymium and Americium Trihydroxides," ONWJ/LBL-15055. LBL Reports 3. H. Nitsche and N. Edelstein,"Thermodynamic 1. N. Edelstein, J. Bucher, R. Silva, and Properties of Chemical Species in Nuclear Waste: H. Nitsche, "Thermodynamic Properties of Chemical I. Carbonate Complexation of Np(V) in Near Neu Species in Nuclear Waste: Topical Report," tral and Basic Solutions: Topical Report," ONWI/LBl-14325. ONWI/LBL-14935. 2. R. J. Silva, "Thermodynimic Properties of 4. J. J. Toman, "Convolution Techniques in Chemical Species in Nuclear Waste: Topical Analytical Electrochemistry," Ph.D. thesis, Report. The Solubilities of Crystalline LBL-14429.

255

Work for Others

1. National Aeronautics and Space Administration (NASA) a. Theoretical Studies of Formyl Radical Formation In Selected Combustion Reactions* William A. Lester, Jr., Investigator'

I. WORK IN PROGRESS

Ab initio Hartree-Fock, multiconfiguration t i Hdrtree-Fock, and configuration interaction •^'thnrfs are being applied to important problems ut combustion chemistry, with particular emphasis H2CO+OH ,. on emission processes in flames. An important intermediate that contributes to flame spectra is HC0(2A") + H 0 the formyl (HCO) radical which has a low-lying 2 electronically excited state {A^r:) that lies ~27 kcaWmole above the ground (X ^A'j state. It is

Z important to know the fraction of HCO formed HCO( A)+H20 directly in the A state.

Fig. 1.1. Energy correlation diagram for H C0 + The most relevant reaction is 2 OH » HCO + H20. (XBL 816-2351)

H?C0 OH - - HCO + H?0 (1) Another reaction relevant to HC0(A2Ii) forma Its energy correlation diagram is shown in Fig. tion is 1.1. The minimum energy pathway and the tronsi- tion state structure for the ground state ?A' + + CH2 0 - -H HCO (2) surface maintains a plane of symmetry. The cal culated transition-state structure shows that the Formaldehyde {H C0) in its ground and excited attacking 0 atom is nearly collinear w-th the 2 electronic state is a stable intermediate in this attacked CH tond. Large basis sets and CI methods reaction. HC0(A2II) originates from H2CO (1n»n*), must be used for quantitative accuracy. H2C0{1Tr*Tf*), and HjCOf3!*^*). Calculations are under way to determine the transition-state struc f The excited state surface corresponds to .he ture for the various elementary steps, as well as second state of singlet spin. Special techniques the transition state structure and energy barrier and methods are required to treat excited states. for Determination of the transition state is in progress. CH2 + 0- -H2C0

*This work was supported by the Ames Research Center, NASA, under Contract No. A 86130B (LML). Equipment was purchased through the National Science Foundation. ^Scientific Staff member at LBL operating under Contract No. DE-AC03-765F00098. 2. Office of Research

a. Structure and Performance of Al203* Donald H. Boone and Alan V. Levy, Investigators

Introduction. The protection of structural phase, high-platinum content outer zone through a materials in high temperature oxidizing and hot two-phase structure to a single-phase NiAl-Pt corrosion conditions that occur in the combustion phase coating. zones of gas turbines and diesel engines is pro vided by the formation of a protective oxide. In In all cases, a zone of Pt enrichment was found many cases the requirements of increased effi at the surface, extending varying distances into ciencies and higher operation temperatures have the coating even though these coatings are pro resulted in a decrease in the lifetimes of an duced by the same initial deposition of a Pt layer engine and its components. For this and other (8 pm) followed by an aluminizing treatment. This reasons much effort has been directed toward the suggests essentially inward aluminum diffusion use of thin protective coatings which are designed through the initial Pt-rich phase found on the to be compatible with higher strength substrates surface. and to form a protective oxide. One such system is the so-called diffusion aluminide coating ap Hot corrosion tests confirmed a strong effect plied to both nickel and cobalt base superalloys. of the test conditions on the protection provided Protection is provided by the formation of an by the addition of Pt, as well as an effect of Al^Ch rich layer and degradation occurs by oxide the specific coating structure present. While a spallation and/or fluxing in cyclic oxidation and large beneficial effect of Pt was found in furnace hot corrosion. hot corrosion testing at 9QQ°C, little if any improvement was found at 700°C. The single phase The addition of noble metals to these coatings high Pt-Al content surface fhase structure was has been reported to increase their protection in found to be more corrosion resistant, particular both oxidation and hot corrosion environments. ly at 900°C. Indications rf a strong substrate Little is understood of the reason for these alloy composition effect i-ere also seen, with the reported improvements and of the interactions coatings on some alloys showing a much stronger between the noble metal, often platinum, the alu "Pt effect" than on othe's. minide, the substrate, and the protective oxide. A research effort was initiated to establish the These and other tests indicate the probable structural features of noble metal enhanced alu effect of the Pt in limiting the concentration of minide coatings. Also being investigated are certain elements at the surface and the subsequent coating formation characteristics, mechanism of effects of these elements on the structure, com interdiffusion, degradation modes and behavior positions, and protection of the oxide that forms. under a variety of elevated-temperature, Previous studies have reported a possible effect simulated-combustion environments. of the Pt to be the formation of a higher purity AI2O3 protective oxide. Since AI2O3 has been found to offer little resistance to basic fluxing 1. PLATINUM MODIFIED ALUMINIA COATINGS* in low temperature corrosion, a limited Pt effect would be expected. Lori Purvis and Donald Boone These hypotheses are being explored in a study Although limited documentation of the structure of both the mechanism of formation using con and phases of platinum modified aluminides exist trolled pre-aluminizing diffusion treatments and in the literature, the implication of earlier the specific activity of aluminizing coating studies has been that the platinum containing cycles. Substrates with controlled addition of coatings have a standard rtructure and excellent potentially critical elements such as Ti and Hf protection in a variety of environments. Prelim are also being studied. inary evaluation of a number of experimental and commercially available coatings, however, has indicated the existence of a wide range of struc tures. These vary from an essentially single- *8rief /ersion of LBL-15668.

*This work was supported by the Office of Naval Research, Department of Defense under Government Order No. N 00014-82-F-0055. + Scientific Staff numbers at LBL operatinq under Contract No. DC :C03-76SF00098. 257

b. Electro n-P ho n on Coupling and the Properties of Thin Films and Inhomogeneous Superconductors*

Vladimir Z. Kresin, Investigator

Introduction. This research is concerned with the study of several interconnected problems. Contacts^ containing superconducting and normal A brief version of LBL-12699; Phys. Rev. B 25, films, have been studied. It is particularly 157 (1982). interesting to consider the proximity systems superconductor-semiconductor (S-SC) and superconductor-semimetal (S-SM) because, in this way, 2. JOSEPHSON TUNNELING AND PROXIMITY EFFECT it is possible to induce the superconducting state in new materials. Josephson tunneling into The structures S -M -I-SY containing the a proximity system is another example of an a e proximity system, for example, Nb-I-Al-Pb have interesting phenomenon. The properties of such attracted a lot of interest particularly in con systems are very sensitive to the strength of the nection with the investigation of new systems electron-phonon interaction, and this interaction with artificial barriers. The thickness and tem should bp included directly in the theory. perature dependences of the maximum Josephson current 1^ have been investigated. It turns out

that IM decreases with increasing L0 and that the 1. SYSTEMS CONTAINING THIN FILMS sharpness of this decrease depends strongly on the

ratio of the energy gaps &0/AY and on the strength A. Critical temperature of the electron-phonon interaction. If M is a

A theory of the proximity effect can be superconductor (T° > TJj, then I„ depends on the developed o« tiie basis of the method of the electron-phonon coupling \ even if T > Ti|. The thermodynamic Green function. The electron- phonon interaction can be included directly. As typical temperature dependence 'i • shown in Fig. a result one can get the following expression for 2.1.

Tc of the proximity system Sa - Ms:

*T! A brief version of LBL-15647, IEEE Transactions (l) Electron Devices (1983).

where T£ is the critical temperature in the absence of the proximity effect, y ^ 1.78, p =

(vg/va) (LB/La}( La and L6 are the thicknesses

of the films, \>rj and \>a are the densities of the states, uM = i'^rM* = i2/U2+r2), r = 2 *T S(vaLa is the tunneling matrix element, S is the area of the contract, io is the phonon frequency, and <---> means average over the phonon spectrum. If the 6 film is a semi

conductor, then Tc can vary as a function of the electron concentration.

B. Si ze quantization

If the semiconductor (or seminietal) film is size-quantizing, the density of states oscillates

as a function of LB and according to Eq. (1),

Tc becomes a non-monotonic function of L6.

A perfectly realistic situation is one in wnich only the lowest energy level is filled (e.g., in Bi fi1ms up to In * 5 x 102 A). Then Fig. 2.1. The dependence IM(T) for the the geometry of the Fermi Tine results in the Pb-Cu-PbO-Pb system; solid line is the theoretical appearance of peculiar charge density waves, lat curve, open points the experimental data (S. Green- tice instability, and structural transitions. spoon and H. Smith).

*This work was supported by the Office of Naval Research under Contract No. N00014-82-F-0103. Scientific Staff member at LBL operating mder Contract No. DE-ACD3-76SF00099. 258

3. WORK IN PROGRESS 1982 PUBLICATIONS AND REPORTS

The critical temperature of the transition to Refereed Journals the superconducting state can be increased in several ways. The softening of the phonon spec 1. V. 1, Kresin, "Influence of Electron-Phonon trum is one of the main mechanisms, and we are Coupling on Superconducting Contacts and the going to investigate this mechanism in detail. A Properties of Superconductor-Semimetal (or Semi particularly interesting case is connected with conductor) Systems," Phys. Rev. B 25, 157 (1982); the contribution of low modes u < Tc. It turns LBL-12699. out that the dependence of Tc on the position and intensity of the low peak is non-trivial. LBL Reports This problem is interesting also from the point of view of the search for non-^phonon mechanisms 1. V. Z. Kresin, "Josephson Current in Proximity of superconductivity. Junction," submitted to IEEE Transactions Electron Devices," LBL-15647.

Invited Talks

1. V. Z. Kresin, "Critical Temperature of Proximity System," Bell Laboratories, Hurray Hill, New Jersey, July 15, 1982. 259 3. Electric Power Research Institute (EPRI)

a. Phase Equilibria for Fixed Bed Gasification Products, Byproducts, and Water*

John M. Prausnitz, Investigator

Introduction. Many coal-gasification The equilibration section of the apparatus is processes include a quench step where the hot composed of an equilibrium cell enclosed in a effluent gas from the gasifier is cooled quickly heated air hath. The quartz equilibrium cell has by water. This quench step is necessary to strip a MONEL flange clamped on each end. The glass heavy tar components ai.c entrained ash from the construction allows viewing the cell contents at gas prior to further processii..-1. Current designs experimental conditions. for quench steps operate at temieratures near or below 250°C. Either three or fo.«r phases may be In the sampling section, samples of each phase present in the quench vessel: a vapor phase, a are withdrawn from the cell, using commercially light hydrocarbon or oil phase, an an-0011''' liquid available pressure generators. Samples are phase, and a heavy hydrocarbon or tar phuse. To flashed completely to form vapor phases. Liquid design the quench operation and subsequent separ sample* {300 pi) are transmitted to vaporization ation steps, phase equilibria must be available. vessels (1 liter) through high-pressure, 6-port Tl- ie equilibria must be correlated by some molec chromatographic valves. ular model so that limited mutual solubility data may be used to predict solubilities at other Our preliminary experimental results for temperatures, pressures, and compositions. lutidine/water and for benzene/water are in good agreement with previously published data. Molecular-thermodynamic models, capable of representing complex phase equilibria, contain parameters that are related to the energies of 2. THEORETICAL METHODS FOR CORRELATION OF PHASE interaction and to the sizes of the various mole EQUILIBRIA cules in the mixture. These parameters must be obtained by fitting the model to vapor-liquid- Frank E. Anderson, Edmundo G. Azevedo, Dorothea liquid or mutual-solubility data. A literature Luedecke, and John M. Prausnitz search for such data has been completed; we have found that w&ry few fundamental data have been There are two thermodynamic procedures for the published. Therefore, we have initiated an correlation of phase-equilibrium data. The first experimental program. uses liquid-phase activity coefficients and vapor- phase fugacity coefficients; we calculate vapor- phase and liquid-phase properties by two different 1. MEASUREMENT OF PHASE EQUILIBRIA models. For the vapor, we use a modified version of the Redlich-Kwong equation of state suitable Frank E. Anderson, Dorothea M. Luedecke, and John for the vapor phase alone. For the liquid phases, M. Prausnitz we calculate activity coefficients by some liquid- mixture model such as UNIFAC. To measure liquid-liquid equilibria for binary aqueous-organic mixtures, we have constructed a In the UNIFAC method, we divide each molecule stirred quartz equilibrium cell from which we can into functional groups. We relate the activity remove samples at pressures to 150 bar and temper coefficient of a component to the sum of the atures to 250°C. Samples are analyzed using gas- functional-group interactions. We account for liquid chromatography. We are currently measuring the size of the functional groups through group- liquid-liquid equilibria for the benzene-water volume parameters, available from crystallographic system, because a large body of experimental re measurements. The arcivity coefficient calculated sults already exists for this system; therefore, by UNIFAC depends or composition and temperature. our results can be compared to those from other The UNIFAC interaction-energy parameters must be sources. obtained from fitting the UNIFAC model to experi mental data. This procedure works well over a We cliarqe the LiHparatus with the mixture of limited temperature range. interest, set the temperature, measure the compo sition of each liquid phase, and measure the total The second procedure calculates fugacity pr

*Tnis work was supported by the Electric Power Hesutirch Institute (EPRI) under Contract lio. RP 1901-1 through an agreement with the Director, Otfu.if (jf Lntryy Research, U.S. Department of liu-MW under Contract No. DE-AC03-76SF00098. 260 of state; we use an equation of the van der Waals chemical equilibria on the equation of state. form. For the repulsive part, we use an expres sion of the Carnahan and Starling type for hard bodies. For the attractive part, we use a simple 1982 PUBLICATIONS AND REPORTS form similar to that used in the Redlich-Kwong equation. Our model also accounts for dimeriza- For publications see section on "High-Pressure tiun of hydrogen-bonding species {e.g., water, Phase Equilibria in Hydrocarbon-Water (Brine) phenolics, pyridines) through superposition of Systems." 261

b. Inhibitive Salts for Reducing High Temperature Oxidation and Spallation* David P. Whittle, Investigator

Introduction. It has been known for many oxides as a means of improving resistance to years that the addition of small amounts of reac scale spallation and oxidation. tive elements to heat resistant alloys produces a marked improvement in the alloy's behavior under C""lic oxidation conditions. More recently, it has ueen shown that fine dispersions of a wide 1. OXIDATION OF Ni-Cr AND Co-Cr ALLOYS COATED range of stable oxides in the alloy have essen WITH REACTIVE ELEMENT SALTS tially the same effect. Metallic additions affect the growth rate and the possible mech«..ism of Stephen Smith, Ajaya K. Misra, and scale development and result in increased adhe David P. Whittle sion. However, oxide dispersions also affect the initial transient stage of oxidation, making it The object of this program is to introduce possible to develop a continuous protective scale various reactive specimens to the surface of high (namely, ^03 or Al2O3) at alloy Cr and Al levels temperature alloys and to study the effect on sub below those required in the absence of a dispersed sequent oxidation. oxide. Thus, in general, oxide dispersions are better than metallic additions, although they are The techniques used for surface app.ication not as conveniently produced, requiring either a were either hot dipping the alloy into the nitrate powder-metallurgy route or an impractical internal solution of the reactive species or -.nodically oxidation treatment. depositing a coating from the same solution. De composition of the resultant coating to oxide, at An alternative approach is to deposit the 400 C, was followed by oxidation at 1000°C in active element oxide as a surface coating, since static air. it is probable that, even in true dispersion con taining alloys, it is only the surface concentra Initial results indicate that there is a tion that is important. A surface coating beneficial effect afforded by selected reactive technique also possesses the obvious advantage element oxides such as La and Y, when applied to that it can be applied to large, complex or in alloys that are established 0263 formers. accessible assemblies or components already in Ni-25£ Cr coated with the La salt was oxidized service. under cycling conditions—20 hr cycles—at 1000°C. After 300 hr total exposure, a very „nin Cr-fls The idea of surface coatings of this type is scale was observed. In contrast, an uncoated not new; indeed it was included in the original alloy of this composition, oxidized for 100 hr at patents of the rare-earth effects,1»^ although it 1000 C, developed a much thicker CrgO^ scale. does not appear to have been inve'.tigated since that iia'a. What is new, however, is a more com plete understanding of the rare-earth effect, which makes it very appropriate to examine the 1. L. B. Pfeil, U. K. Patent No. 459848 (1937). feasibility of using surface coatings of stable 2. L. B. Pfeil, U. K. Patent No. 574088 (1945).

*This work w.is supported by the Electric Power Research InstitutL (EPRI) under Contract Number RP ??61-1, through an agreement with the Director, Office of Energy Research, U.S. Department of Enerqy under Contract No. DE-AC03-76SF00098. *Dr. Whittle died in July 1982. This report has been prepared by Or, Stephen Smith. Since Dr. WhiUle's death, Dr. J. Stringer of the Electric Power Research Institute has been acting as tech nical advisor, pending the appointment of a full- time successor. 262

c. Investigate New Fuel Cell Electrolyte and Electrode Concepts*

Philip N. Ross, Investigator

Introduction. Phosphoric acid is the electro rpm range were analyzed with the i-* vs »-l/2 cor lyte currently in use for commercial hydrogen-air relation to verify the first order dependence of cells. It is a relatively weak acid (pK = 2.1), the reaction kinetics on the Og surface concen and there is specific adsorption of phosphoric tration. Since the H3PO4 additions did not affect acid anions on Pt surfaces that probably inter the well-defined diffusion limiting currents (i|J fere negatively with the oxygen reduction reac in the 0.1 M TFMSA solution, the measured value tion at Pt electrodes. Trifluoromethane sulfonic of I'L was used to determine the diffusion-free acid (TFMSA) is a very strong acid, and specific kinetic current, ij(. A summary of mass transport adsorption of the anion on Pt in 0.1 M TFMSA and kinetic data appears in Tables 1.1 and 1.2, appears to be minimal as determined by recent respectively. measurements. Therefore, it is expected that oxygen reduction on Pt electrocatalysts in TFMSA Experimental findings and their analysis have would proceed at higher rates than in phosphoric indicated that (a) O2 reduction is first order acid. Technologically, the problem with TFMSA as with respect to the surface concentration of O2 a fuel cell electrolyte is that in t.ie concentra in all solutions; (b) the diffusion limiting cur ted form needed in practice, the aciJ wets the rent, iL, is lower by -15% in the 0.7 M H3PO4 polytetrafluoroethylene (PTFE) hydrophobic bond solution than in the 0.1 M H3PO4 solution than in ing agent used in gas diffusion eiectrodes caus the 0.1 TFMSA solution; (c) iL in the 0.1 M TFMSA ing a collapse of the three-phase interfacial solution is not affected by H3PO4 additions (up structure. It is hypothesized that this wetting to 11.4 mM); (d) O2 reduction kinetics in 0.7 M is because of the CF?- functional group and H3PO4 are slower than in 0.1 M TFMSA by a factor that multibasic homologs of this acid, e.g., of approximately 15; (e) additions of H3HP4 in tetrafluorethane -1,2- disulfonic acid (TFEDSA), the mM range to a 0.1 M TFMSA solution signifi would not wet PTFE. Another technological prob cantly lower the reaction rate; and (f) Tafel lem with TFMSA is its relatively high volatility slopes are not significantly affected by addi at practical operating temperatures (>100°C). It tions of H3PO4 to the 0.1 M TFMSA solution. is felt that higher homologs of TFM5A would have a lower vapor pressure, so that multibasic higher homologs of TFMSA may have all the advantageous A thorough quantitative analysis of the properties of this acid but with low volatility poisoning effect of H2PO4- is prevented by the and with the desired wetting properties. The lack of anion coverage data for the H2P04~ con object of this program is to study oxygen reduc centrations used in the present study. However, tion on the family of perfluoroalkylsulfonic acids to determine whether or not the desirable characteristics of TFMSA are intrinsic to this class of organic compounds. Table 1.1. Values of the B Coefficient for O2 Reduction in TFMSA, H3PO4, and Their Mixtures.

1. THE EFFECT OF H2P04- ANION OF THE KINETICS OF OXYGEN REDUCTION ON Pt+ B/mA-cnr2 sec1'2 P. C. Andricacos and P. N. Ross, Jr. Electrolyte Ia D In view of the existing evidence in favor of n non-adsorbing nature of TFMSA on Pt,l we have chosen this acid as the baseline from which the 0.1 M TFMSA 0.459 0.499 effect of adsorbing anions on the O2 reduction kinetics can be observed. For this purpose, mM 0.1 M TFMSA + 0.38 mM H3PO4 0.459 0.505 concentrations of H3PO4 were added to a 0.1 M TFMSA solution (pH = 1), and the O2 reduction 0.1 M TFMSA + 11.4 mM H3PO4 0.459 0.496 kinetics were measured with the rotating disk electrode (RDE) method. Sin^ H3PO4 is a weak 0.7 M H3PO4 0.382 0.423 acid, (Ki = 7.6xl0"3) mM addition to a strong acid solution does not affect the pH significant ly. The O2 reduction kinetics were also deter

mined in a 0.7 M H3PO4 solution that has the same a 1 2 pH (=1) as C.l M TFMSA. RDE data in the 100-900 Sl0pe Of l'l_ VS a) / . ^Slope of i~l vs u-!/2 where i[_ is the diffusion limiting current density and i is the measured current under mixed diffusion-kinetic control. *This work was supported by the Electric Power Research Institute (EPRI) under Contract No. B = 0.62nFcbD2/3v-1/6, where n = 4 for the RP-1676-2 through an agreement with the Assistant 4-electron reduction of O2 to H2O, cD is the bulk Secretary for Conservation and Renewable Energy, concentration of O2, D is its diffusion coeffi U.S. Department of Energy under Contract No. cient, and v is the electrolyte kinematic DE-AC03-76SF00098. viscosity. 263

Table 1.2. Kinetic Parameters of O2 Reduction on Pt in TFMSA, H3PO4, and Their Mixtures.

lK/mA-cnr2 Tafel slope/V-dec-*

[H2P(V3 E/y E/y Electrolyte mol-dm-3 C.700 0.800 0.900 >0.800 0./00-0.800

0.1 K TFMSA - 52 9.4 1 0.85 0.117-0.135

0.1 M TFMSA + 0.38 mM H3PO4 2.9xl0"5 22 4.2 0.4 N.D. 0.114-0.140

0.1 M TFMSA + 11.4 mM H3PO4 8.7xl0~4 10 1.8 0.2 N.D. 0.127-0.137

0.7 M H3PO4 7.3xl0-2 5 0.7 0.06 N.D. 0.113-0.135

NOTE: N.D. is not a well-defined Tafel slope in this region.

:xtrapolations from the literature values2 for 1. 0. Petrii, 5. Vasina, and L. Lukyanycheva, 5 ;he 2.9xl0~ M H2PO4- (Table 1.2) anion concen Soviet Electrccfcem. \7_y 1144 (1982). tration yield a surface coverage of 25%, assuming 2. G. Horanyi, E. Rizmayer, and G. Inzelt, J. that three Pt sites are blocked by each anion. Electrcanal. Chem. 93, 183 (1978). The observed factor cf 2.5 in the decrease in 0? reduction kinetics for this H2PO4- concentration cannot then be explained on the groups of site blocking only. 1982 PUBLICATIONS AND REPORTS

It was concluded that a combination of site LBL Reports blocking of Pt by H2PO4- and activation energy changes in the adsorption of O^H in the presence 1. P. N. Ross, Jr. and P. Andricacos, "The of H2PO4- account qualitatively for the signifi Effect of H2PO4- anion on the Kinetic of Oxygen cant decrease in Oj reduction kinetics observed Reduction on Pt," to be published in J. Electro- when very small amounts of H3PO4 are added to a anal. Chem., LBL-15266. 0.1 M TFMSA solution (pri = 1). ?.. P. N. Ross, Jr., "Evaluation of Tetrafluor- * * * ethane -1,2- Disulfonic Acid as a Fuel Cell Electrolyte," to be published in J. Electrochem. i" Brief version of LBL-15266. Soc, LBL-14762. 264

d. Improved Beta-Afurrrin? Electrofyfec for Advanced Storage Batteries* Lutgard C. De Jonghe, Investigator

Introduction. Men sodium beta or beta" 1. DEGRADATION OF SODIUM BETA" -ALUMINA: EFFECT alumina solid elsctrolytes are subjected to ionic OF MICROSTRUCTURE* charge transfer in sodium/sodium or in sodium/ sulfur cells, degradation of the electrolytes may A. C. Buechele, Lutgard C. De Jonghe, and David occur. The electrochemical degradation may take Hitchcock different forms, as was recently discussed in Ref. 1. Mode I degradation involves the cathodic Acoustic emission detection was used for the plating of sodium into a pre-existing surface study of failure initiation of Na betaM-aljmina flaw on the sodium side of the electrolyte, caus electrolytes in sodium/sodium cells. The two ing crack extension above some critical value of different microstructures examined, A and 8, are the electrode current density. Mode IT involves shown in Fig. 1.1. a possible internal deposition of metallic sodium during charge transfer through an inhomogeneous 2 The observed critical current density for solid electrolyte. initial crack propagation was related to the dis tribution of pre-existing active flaws in the A sensitive method for detecting the initia surface of the electrolyte in contact with the tion of crack propagation, acoustic emission mon negative sodium electrode and to the current dis itoring, was used in the present investigation. tribution on the electrode. The statistical nature of the active flaw distribution led to a corresponding Weibull distribution of the current densities necessary to initiate Mode I degrada 1. L. C. De Jonghe, L. Feldman, and A. Buechele, tion. The average critical current densities for the two specimen types were 145 mA/cm2 for micro- 0. Mat. Sci. 16, 780 (1981). 2 2. L. C. De 3ohghe, ,]. Electrochem. Soc. 129, structure B and 640 mA/cm for microstructure A. 752 (1982). The electrolyte with smaller grain size has a

Fig. 1.1. Comparison of the electrolyte microstructures. Scanning electron micrograph of electrolyte etched in H3PO4. (XBB 815-4088)

*This work was supported by the Electric Power Re search Institute (EPRI) under Contract No. RP 252-3, through an agreement with the Assistant Secretary for Conservation and Renewable Energy, U.S. Depart ment of Energy under Contract No. DE-AC03-76SF00098. 265

significantly higher threshold for failure initi LBL Reports ation. Corrections for the non-uniformity of the current distribution were calculated and led to 1. L. C. De Jonghe, "Degradation Mechanisms of average failure current densities at 240 and 700 Sodium Beta Aluminas," LBL-14365. mA/cm^. The ratio of the average critical cur rent density is comparable to that of the average 2. A. Buechele, L. C. De Jonghe, and grain size or the average length of the fraction D. Hitchcock, "Degradation oi" Sodium Beta" with large grains. Alumina: Effect of Microstructure," LBL-13188 * * * Rev.

f 3. L. C. De Jonghe, A Buechele, and K. H. Yoon, Brief version of LBL-13188 Rev. "Grain Boundaries and Solid Electrolyte Degrada tion," LBL-14150. 198? PUBLICATIONS AND REPORTS Invited Talks Refereed Journals 1. L. C. De Jonghe, "Degradation Phenomena in 1. L. C. De Jonghe, "Transport Number Gradients Sodium Beta" Solid Electrolytes," Compagnie and Solid Electrolyte Degradation," J. Electro- Generale d' Electricite, Maroussis, France, June chem. Soc. 1^9, 752 (1982). 1982.

2. L. Feldman and L. C. De Jonghe, "Initiation 2. L. C. De Jonghe, "Performance of Sodium Beta" of Mode I Degradation in Sodium Beta Alumina Alumina in Na/Na and Na/S Cells," Dow Chemical, Electrolytes," J. Mat. Sci. 14, 885 (1982). Walnut Creek, California, September 1982.

3. L. C. De Jonghe and A. Buechele, "Chemical 3. L. C. De Jonghe, "Solid Electrolytes for the Coloration of Sodium Beta Altiminas," J. Mat. Sci. Na/S Storage Battery, Electric Power Research J7, 885 (1982). Institute, Palo Alto, California, June 1982. Appendices 267

Appendix A

Materials and Molecular Research Division Personnel

Scientific Staff

1982 Postdoctoral Investigators and Other Scientists Graduate Students

Neil Bartlett R. Brusasco T. Mallouk B. Desbat B. McQuillan H. Dove J. Nitschke C. Platte F. Okino T. Richardson G. Rosenthal A. Tressaud In. Totsch J. Verm'olle A. Materfeld

Alexis Bell J. Baker R. Dictor T. Frederick R. Hicks 0. Jordan M. Reichmann J. Rieck R. Underwood P. Winslow

Robert Bergman W. Hersh P. Becker H. Matturro T. Bischoff J. Bonfiglio H. Bryndza J. Buchanan P. Comita T. Gilbert N. Jacobson A. Janowicz L. Newman C. Nitsche R. Periana-Pi'lai M. Seidler P. Seidler K. Theopold H. Wax W. Weiner G. rang

Robert Bragg D. Baker L. Henry J. Hoyt J. Johnson B. Mehrotra A. Pearson

D. Davis J. Bularzik C.B. Meyer E. Faizi G. Rosenblatt S. Hahn K.Ward J. Gibson 1982 Postdoctoral Investigators and Other Scientists Graduate Students

Brewer (cont'd) R. KcCurdv R. Stimach

John Clarke C. Hilbert R. Koch H. Mamin J. Martinis P. Maxton R. Mlracky J. Pelz D. Sellgson F. Wellstood

Marvin Cohen S. Froyen C.T. Chan S. Louie K.J. Chang D. Vanderbilt M-Y. Chou M. Hybertsen P. Lam Z. Levine J. Northrup

Robert Connick C. Chieng D. Horner K. Krushwitz M. Wagner W. Tinl K. Ward

Lutgard De Jonghe M. Armand C. Balfe M. Chang A. Buechele H. Schmid C. Cameron K-h. Yoon M. Chang J-C. Chen M. Herrara D. Hitchcock B-H.Hwang S. Kikugawa Y. K1m C. Mailhe R. McClelland G. Raj M. Weiser S. Wu

Didit de Fontaine 0-P. Simon E. Colas W. Teitler H-M. Jang K. Krishnan J. Kulic R. Pro H-C. Tsai

Norman Edelstein K. Abu-Dari J. Arenivar N. Bartlett R. Andersen S. Barclay S. Brown S. Bachrach P. Becker J. Conway J. Bucher J. Boncella K. Raymond S. Davis B. Borgias G. Seaborg P. Edwards J. Brennan 269

198? Postdoctoral Investigators and Other Scientists Graduate Students

Edelstein (cont'd) A. Streitwieser T. Hayhurst T. Chung D. Templeton D. Kagan M. Derzon A. Zalkin R. Klutz S. Fletcher J.C. Krupa G. Freeman W. Muller B. Gilbert C. Or/ig G. Girolami K. Rajnak M. Hal pern G. Shalimoff S. Kinsley L. Tempi eton L. Loomis H-K. Wang H. Lyttle G. Wong R. Moore 0. Zhang D. O'Donovan D. Zhu V. Pecoraro R. Planalp R. Scarrow R. Shinomoto K. Smith J. Toman T. Tufano S. Un G. Williams

Anthony Evans B. Dalgleish W. Blumenthal W. Kri«en L. Cheng J. Lamon S. Chiang D. Marshall H.S . Choy M. Omori G. Crumley T. Uchiyama T. Dabbs M. Drory K. Faber Fu C-Hr.. Hsueh S. Johnson J. Low H-C. Lu J. Maasberg J. Marion C. Ostertag C. Rossington W. Shubin M. Thouless H-C. Tsai

0. Coates H. Abbasi S. Lympany M. Hall R. Moreeu T. Huh V. Nakano H-l: . Lee D. Rieck C. Palmer H. Rau K. Spring

R. Osario M. Robbins J. Tersoff R.:!. Victora

Iain Finnie S. Chavez A. McGee S. Soemantri 270

1982 Postdoctoral Investiqators and Ottier Scientists Graduate Students

Andreas Glaeser J-C. Chen

Ron Gronsky E. Boden L. Andersen A. Goldberg C. Clark J. Penisson P. DeRoo P. Rez S. Cheruvu Steeds Howe

J. Juk i L. Tanner Ea. R. J. M. a. G. E.

Eugen Haller S. Pearton

Charles Harris M. Alivasatos H. Berg a. Brown George S. Goncher G. A. Harris C. Parsons P. Whitmore ilsinz Heinemann Bell Bergman J.Evans Levy Somorjai Vollhardt

Dennis Hess C. Blair A. Wasita L. Williams

Carson Jeffries P. Bryant J. Culbertson B. Furman G. Held E. Pakulis J. Perez J. Testa

Harold Johnston R. Carlson J. Hebel P. Estacio S. Solomon 0. Swanson

William Jolly K. Bomben H. Ajmani C. Eyermann D. Beach 271

1982 Postdoctoral Investiqators and Other Scientists Graduate Stude

Yuan Lee R. Buss R. Baseman 0. Dutuit R. Brudzynski P. Felder S. Bustdroente J. Hepburn L. Butler J. O'Brien H. Covinsky H. Schmidt J. Frey J. Van Den Biesen C. Hayden S. Huang 0. Krajnovich T. Minton D. Neumark H. Okumura R. Page J. Reutt G. Robinson P. Schulz H. Valentine M. Vernon P. Weiss A. Wodtke L. Veh

William Lester L. Johnson R. Barnett K. Jolls C. Oateo P. Reynolds R. Grimes L. Johnson

Alan Levy W. Coons H. Arnal I. Finnie E. Ettehadieh T. Foley H. Frank R. Glardon K. Johnson M. Holt I. KHafas J. Humphrey F. Pourahmadi F. Pourahmadi H-L. Tsai P. Tom P. Turi W. Worrell

S. Louie S. Froyen C-T. Chan J-Q. Wang J. Willi:'*

Bruce Hahan T. Turner

Richard Marrus J-P. Briand P. Drell A. Chetioui C. Hunger E. Commins C. Tanner H. Gould J, Leavitt M. Mittleman H. Prior H. Shugart

William Miller C. Cerjan D. Ali L. Hubbard T. Carrington 272

1982 Postdoctoral Investigators and Other Scientists Graduate Cedents

Miller (cont'd) S. Shi P. Dardi S. Gray S. Schwartz 8. Waite

C. Bradley Moore L. Aljibury A. Abbate C. Chi-Ke D. Bamford J. Jasinski J. Frisoli A. Kung F. Hovis D. Nesbitt A. Langford P. Ogilby W. Natzle H. Petek J. Wong L. Young

John W. Morris, Jr. M. Hong G-M. Chang G-X. Nu D. Dietderich R. Kopa D. Fior H.J. Lee D. Frear L-S. Li B. Fultz R. Ogawa M. Hong D. Powell B.Johnson-Walls J. Sanchez H-J. Kim M-C. Shin Y-H. Kim Y. Tomota E. Kostlan H. Lee H-L. Lin T. Mohri K. Sakai J. Sanchez S. Shaffer Y-C. Shin H-K. Shin M. Strum L. Summers I-w. wu K. Xue

Earl Muetterties P.. Feltham J. Bleeke D. Keinekey R. Burch J. Kouba H. Choi J. Stein W. Cwirla M. Tachikawa T.M. Gentle V. Grassian D. Klarup Y. Otonari G. Schmidt K. Shanahan S. Slater M. Tsai R. wexler

Rolf Muller W. Giba D. Barkey G. Nazri C. Coughanowr J. Farmer D. Fischl R. Gyory 1982 Postdoctoral Investigators and Other Scientists Graduate Students

E. Pawlikowski H. Berg D. Bernardi V. Edwards A. Hauser N. Matlosz H. Orazem P. Pierini T. Risen P. Russell G. Trost

Donald Olander M. Balooch M. Derzon R. Kohli D. Dooley A. Hachiels M. Farnaam N. 3hashi P. Goubeault S. Zhou K. Kim G. Mitchem D. Sherman F. Tehranian S. Yagm'k

Joseph PasJc P. Spencer A. Tomsia F. Zhang

Norman Phillips J. Flouquet W. Fogle t. Hornung C. Lisse J. Lasjaunias H. Mayberry K. Matho J. Van Curen

Alexander Pines R. Goldberg A. Bielecki H. Fujiwara J. Baum U. Nitsan H. Cho H. Zimmennann G. Drobny R. Eckman J. Garbow J. Millar B. Oh E. Schneider A. Thayer R. Tycko Y-S. Yen D. Zax

Kenneth Pitzer K. Balasubramanian S-W. Wang

John Prausnitz F. Anderson M. Gibson E. Larsen S. Sepahban W. Whiting J.O. Wong 1982 Postdoctoral Investigators and Other Scientists Graduate Students

Paul Richards H. Levinson J. Bonomo A. Smith W. Challener S. Chiang K. Engelhardt H. Hueschen S. HcBride W. KcGrath G. Tooin

Robert Ritchie N.H. Croft V. Dutta 0. Sarma T. George S. Sutesh S. Ivy K. Johnston T. Lin R. Pendse J-L. Tzou E. Zaiken

Philip Ross P. Andricacos A. Cabrera d. Bardi G. Oerry F. Wagner J. Willsau

Richard Saykally

Henry Schaefer III J. Bicerano M. Col Yin J. Breulet G. Fitzgerald J. Goddard D. Fox R. Pitzer J. Gaw A. Schier R. Grev H. Sokol M. Hoffman M. Vincent T.J. Lee V. Yamaguchi G. Raine P. Saxe

Alan Searcy C. Beruto J. Farnsworth D. Chung A. Hegedus S. Loine H.G. Kim D. Heschi T. Reis Z. Munir E. Thomsen y. Ron Shen C. Chen G. Boyd T. Rasing M-m. Cheung S. Shen S. Durbin L. Shi T. Heinz P. Ye H. Hsiung H. Zhu R. Pecyner H. Tom X-D. Zhu

Da^id Shirley U. Becker A. Baca P. Dabbousi C. Bahr 275

1982 Postdoctoral Investigators and Other Scientists Graduate Students

Shirley (cont'd) W. Heppler J. Barton Z. Nussain R. Davis G. Kaindl T. Ferrett G. Lui N. Glad D. Trevor P. Heimann I. Klebanoff P. Kobrin D. Lindle C. Parks J. Pollard S. Robey D. Rosenblatt A. Schach von Wittenau H. Schulz J. Tobin C. Truesdale

Gabor Somorjai M. Asscher B. Bent R. Casanova E. Benjamin P. Davies J. Crowell F. Delannay R. Fox G. Ertl C. Galik M. Farias E. Garfunkel S. Ferrer A. Gellntan M. Kudo M. Guthrie H. Langell H. Hendewerk C. Leygraf B. Koel R-F. Lin R. Koestner W. McLean M. Levin H. Salraeron G. Lewis N. Spencer T. Lin J. Turner M. Logan H. Tysoe C. Mate B. Naasz D. Ogletree M. Quinlan J. Twiford R. Veates G. Yee F. Zaera

Gareth Thomas J. Davey J. Ahn M. Hall R-S. Caron T. Harvey L. Chan R. Hoel T. Dinger N. Kim J-S. Gau J. Koo A. Jhingan C. Kung K. Krishnan J. Leteurtre C. Kwok X. Meng I-N. Lin R. Mishra A. Nakagawa G. Honks S. Ong J. Penisson L. Rabenberg J. Rayment J. Ruchlewicz W. Salesky M. Sung H. Sarikaya H. Tokushige J. Steeds J. wasynczuk G. VanTendeioo X-F. tfu M. von Heimendahl Y-S. Yoon J. Van A-J. Yang 276

1982 Postdoctoral Investiqators and Other Scientists Graduate Students

Charles Tobias P. Cettou P. Andersen D-S. Doh R. Anderson D . Rajhenbah D. Dees J. Dukovic J. Faltemier K. Hanson W. Hui R. Hyman P. Johnson T. Tsuda H. Verbrugge G. Whitney

'<. Peter Vollhardt V-H. Lai R. Col born D.. Van Horn J. Drage J. King Tane »'. Til set E. Walborsky T. Weidman

Jack Washburn R., Hagstrom R.S. Caron G., Hirsch C. Jou C.. Lampert P. Ling D. Sadana W-L. Lo 1.. Wang T. Kowles T. Sand' D. Sipes T-H. Wei N-R. Wu r-J. Wu T. 2ee

Kenneth Westmacott U. Dahmen J-M. Lang J. Davey A. Pel ton P. Ferguson S. Puranikmath M. Hall L. Wu J. Leteurtre G. Monks J. Pennison J. Steeds R. Schonbucher G. Szaloky M. Von Heimendahl

David Whittle D. Boone H. Akuezue I. Cornet S. Berggren H. Hindam S-H. Choi A. Misra P. Hou S. Smith J-1' . Lee R. Streiff R. Pendse M. Yee F. Yang

M. fjier B. Hale W. Hollingsworth D. Horak' 277

1982 Postdoctoral Investigators and Other Scientists Graduate Students

Winn (cont'd) H. Luftman S. Sherrow

C. Collins J. Weiner 278

Support Stan

Oiyision Administrative Staff C. Peterson - Assistant Division Head, Administration K. McArthur - Assistant Division Administrator

Administration Personnel Purchasing M. Janzen S. Quarello S. Stewart L. Irvin P. Paladini C. Sterling M. Bowman I. Gosiengfiao S. Muir S. Shirey

Technical Editing Special Projects J. Knight E. Skrydlinstci

Administrative/Secretarial Staff

N. Alpaugh S. Gangwer B. Nagaue R. Arcol M. Gill V. Narasimhan H. Atkinson C. Gliebe E. Nil son K. Becky c. Gloria M. Noyd H. Benson c. Hacker A. Ozturkmen H. Besser J. Hoagfolt M. Penton C. Bilorusky D. Israel L. Pham G. Brazil D. Johanson M. Rector K. Brusse H. Johnson J. Shull n. Carmichael P. Johnson J. Smith B. Carter R. Jones c Thur N. Charpentier S. Kaul A. jfeightman K. Denison T. Learned S. Wilde J. Denney S. Macahilig L. Vanac L. Franson D. Merrill C. Voder S. Ewing H. Moore S. Young H. Gaubay B. rtonguchi B. Zambrano

Technical Staff W. Toutolmin - Technical Coordinator

D. Ackland K. Franck J. Kolthuis R. McCurdy S. Smi t G. Baum L. Galovich J. Jacobsen W. Murrel1 H. Sokol E. Benjamine K. Gaugler L. Johnson B. Neil son V. Stumpf 13. Blowers W. Giba P. Johnson J. Patterson C. Thorn F. Boden C. Gibson D. Jurica A. Pentecost P. Tom H. Bowman, Jr. J. Glazer B. Kan L. Purvis G. Tong H. Brendel R. Gray K. Xoshlap H. Riebe P. Turi R. Brusasco A. Gronsky E. Kosllan P. Ruegg K. Wada C. Carter W. Goward U. Krieger t. Scherr R. Wagner B. Chandler H. Harrell H. Kuj'ala t. Scholz M. Wall M. Cima W. Heppler D. MacDonald S. Shaffer H. Weeks A. Davis c. Hickeyr V. Mantyd J. Severns W. Wong f). Dietderich G. Hirsch J. Martinis L. Slamovich N. Yates E. Fong P. Yau 279 i3; 0

Appendix B

Materials and Moltcular Research Division Committees

DIVISIONAL COUNCIL

H. Cohen H. Heinetnann N. Edelstein H. Johnston J. Morris, Jr.

BUILDING AND SPACE COMMITTEE (Includes Buildings 50D, 52, 70A, 72, and the Chemical and Materials Sciences Laboratory) ft. Gronsky R. Muller* D. Meschi A. Zalkin

DIVISIONAL RESEARCH STAFF COMMITTEE ELECTRON MICROSCOPE USERS COMMITTEE

N. Edelstein R. Muller* R. Gronsky P. Rocs* L. Falicov K. Westmacott J. Morris, Jr. K. Westmacott

EQUIPMENT REVIEW COMMITTEE

J. Clarke C. B. Moore A. Evans R. MuITer*

SAFETY AND LABORATORY STANDARDS COMMITTEE

D. Ackland B. Fultz J. Holthuis R. Mulle- S. Smith G. Baum T. Gentle L. Irvin S. Ozturi'nen C. Sterling T. Britt W. Gibi, L. Johnson C. Petersor. S. Stewart D. Davis W. Hemphill D. Krieger H. Rieber I. Summers E. Fong T. Hicitcock K. McArthur J. Severns W. Toutolmin K. Franck H. Hindam D. Meschi* E. Slamovich W. Wong

TECHNICAL STAFF AND SHARED FACILITIES COMMITTEE

L. De Jonghe P. Ross R. Gronsky G. Somorjai J. Morris, Jr. D. Whittle

MMRD Building 62 Building Manager: D. Meschi (Alternate: C. Peterson)

MMRD Building 72 Building Manager: K. Westmacott (Alternate: D. Ackland) 281

Appendix C

List of Seminar*

Surface Science and Catalysis Science

Date Speaker and Affiliation Seminar Title

1-7-82 Prof. L. Schmidt Reactions of NO on Pt at Low and High University of Minnesota Pressures 1-14-82 Prof. G. Ertl Scattering and Deexcitation of Metastable University of Munich Noble Gas Atoms at Surfaces *l-18-82 Dr. W. F. Egelhoff Surface Core Level Shifts in Binary Alloys: National Bureau of Standards AH of Surface Segregation and Chemisorption

1-21-82 Prof. E. L. Park Critical Phenomena in Chemisorbed Leyers University of Maryland

*l-22-82 Prof. H. Siegmann Surface Magnetism and Chemisorption ETH-Zurich and IBM

*l-26-82 Dr. P. Eisenberger X-Ray Scattering Studies of Surfaces: Exxon Research Structure and Melting Phenomena

1-28-82 Prof. H. Gerischer Photoelectrochemical Studies of Semi Fritz-Haber-Institut conductors with Layer Structures Berlin

Dr. J. Rowe Recent Structural Studies of Surfaces Using Bell Telephone Laboratories EXAFS

Dr. R. L. Hartgerink Catalytic Coal Gasification: Mechanisms and Exxon Research Process Development

Dr. J. Chadi Why Do Semiconductor Surfaces Reconstruct? Xerox PARC

*2-12-82 Prof. W. Brenig Kinetic Processes at Solid Surfaces: Theory Technical University and Some Typical Experimental Results Munich

2-18-82 Prof. W. E. Spicer Study of Alloy Surfaces (CuNi, PdAu, P'tCu) Stanford University Adsorbate Site and Geometric Effects and Examples of Relations Between UHV and Atmospheric Pressure Reactions

2-25-82 Dr. a. Kokatailo Zeolite Structure and Catalysis Mobil Research 3-4-82 Dr. T. E. Felter Recent Studies of the Adsorption and Oxidation Sandia, Livermore of Small Molecules Over Single Crystal Surfaces of Transition Metals Using Photo- electron Spectroscopy

3-4-82 Dr. V. Udaya S. Rao Indirect Liquefaction Using Metal-Zeolite DOE-Pittsburgh Energy Catalysts Technology Center 3-11-82 Dr. J. Shinn A Model of the Chemical Structure and Chevron Research Liquefaction Behavior of Bituminous Coal

3-18-82 Dr. F. Herman Recent Developments in the Physics and IBM, San Jose Chemistry of Semiconductor Interfaces 3-23-82 Drs. Y. Huang and J. C. Tang Determination of Surface Structure by Photo- University of Wisconsin electron Diffraction

•Special Seminar Surface Science and Catalysis Science (continued)

Date Speaker and Affiliation Seminar Title

3-25-82 Dr. J. Horsl'jy X-Ray Absorption Edge Resonances as Probes Exxon Research of Catalyst Electronic Structure

3-26-82 Dr. G. B. Fisher The Role of Mechanistic and Kinetic Factors General Motors in the Water Formation Reaction on Platinum

4-8-82 Dr. S. Weller Efficient Catalysts for Coal Liquefaction SUNY, Buffalo

4-14-82 Dr. H. Shulz Initial Selectivity of Fischer-Tropsch Tech. University-Karlsr'ihe CO Hydrogenation

4-15-82 Dr. H. Balooch Molecular Beam Study of Metal Halogen UCB/L8L Reactions

4-22-82 Dr. R. J. Beta Hydrogen on Fe(110): Ordered Phases and IBM, San Jose Temperature/Coverage Dependence

4-29-82 Prof. M. Simonetta Force Field Calculations for Crystallography University of Milan

5-6-82 Dr. R. M. Laine Homogeneous Catalytic Formation of C-N Bonds: Stanford Research Internati Fischer-Tropsch-Like Reactions of Amines With Synthesis Gas

5-13-82 Dr. E. Wymore Balance i;i Industrial Research Dow Chemical

5-20-82 Prof. E. W. Plummer Mysteries of Hydrogen Adsorption (NEW) University of Pennsylvania

5-26-82 Dr. Kenzi Tamaru Selectivity and Mechanisms of COH2 Reaction University of Tokyo on Transition Metals

5-27-82 Prof. C. J. Radke Adsorbed Configurations of Colloidal Molecules University of California at Charged Aqueous-Solid Interfaces Berkeley

6-3-82 Dr. R. L. Schwoebel Hydrogen Trapping in Metals Sandia Laboratories

6-10-82 Prof. S. Y. Tong The Role of Surface Image Potential in Elastic University of Wisconsin and Inelastic Electron Scattering from Surface

6-16-82 Prof. G. Blyholder Matrix Spectroscopy Applied to Surface University of Arkansas Chemistry

6-29-82 Professor J. Oudar Sulfur Adsorption and Poisoning of Metals Ecole Nationale Superieure de Chimie-Paris

7-15-82 Dr. P. A. Thiel The Mechanism of an Adsorbate-Induced Surface Sandia-Livermore Reconstruction: CO on Pt(100)

7-19-82 Dr. K. Tanaka Photocatalytic Oxidation and Reduction of Rikagaku Kenkyusho Organic Compounds over Metal/Ti02 Powders Japan

8-6-82 Prof. J. 8. Pendry X-Ray Absorption Near-Edge Fine Structure: Imperial College The Inside Story London

8-12-82 Dr. J. P. Biberian Adsorption of CI on Si(III): Etching of Si University of Marseille by CI France 283

Surface Science and Catalysis Science (continued)

Date Speaker and Affiliation Seminar Title

8-19-82 Dr. J. C. Frost The Application of Mossbauer Spectroscopy to Heriot-Watt University the Study of Surfaces Edinburgh

Prof. N. Sheppard Professor N. Sheppard - Some Correlations Dr. M. A. Chester;; Between Vibrational Spectra of Hydrocarbons University of East Anglia Adsorbed on Finely Divided Metals and Single England Crystals Metal Surfaces Dr. M. A. Chesters - Some Application of Auger Electron Spectroscopy and Reflection- Absorption Infrared Spectroscopy to the Characterization of Adsorbed Species on Single Crystal Metal Surfaces

8-30-82 Dr. P. A. Thiry HREELS Study of Gas-Metal Interactions: University of Namur Oxygen on CuZn, Oxygen on Magnesium and Belgium Formic Acid on Gold

8-31-82 Dr. S. L. Bernasek Directed Energy Production of Novel Metallic Princeton University Surfaces

8-31-82 Dr. L. H. Dubois Fundamental Studies of the Strong Metal- Bell Laboratories Support Interactions: Chemisorption and Catalysis on Nickel Silicides

9-2-82 Prof. A. Meisel X-Ray Spectroscopic and Photoelectron Karl-Marx Universitat Spectroscopic Investigation of the Electronic Structure of '-latter

9-21-82 Prof. C. Aharoni Effect of Surface Diffusion in the Kinetics University of Pennsylvania of Chemisorption

9-22-82 Dr. J. Klinowski Electron Diffraction and NMR Studies of University of Cambridge Zeolite Structure and Function

9-28-82 Dr. K. Wandelt "Local Surface Dipole Probing Characteri University of Munich zation of Atomic-Scale Surface Roughness"

9-30-82 Professor M. B. Maple "Metallic Oxydation: Its Role in the University of California Oscillatory Reaction of Co and Og Over San Diego Transition Metal Catalysts" lf-7-82 Dr. J. R. Katzer "Selectivity to Alc

10-14-82 Prof. S. W. Benson Entropy Structure and the Transition State: University of Thermochemical View of Catalysis Southern California 10-21-82 Professor W. Maier Hydro-Denitrogenation Studi° University of California Berkeley

10-22-82 Dr. E. Bertel Oxydation of Rare Earths [Er, Yb) and University of Innsbruck Transition Metals (Ti): A Case Study of Austria Three Different Mechanisms

10-28-82 Irof. J. Shabtai Stereo.hemical and Kinetic Aspects of University of Utah Hydrogenation and Hydrodenitrification Reactions Over Sulfided Catalysts

11-4-82 Prof. E. Solomon Photo Electron Spectroscopic Studies of the Stanford University Interaction of CO with ZnO Surfaces 11-5-82 Prof. G. Doyen Quantum Theory of Rotational Excitations in Univtrsity of Munich Molecule/Surface Scattering Surface Science and Catalysis Science (continued)

Date Speaker and Affiliation Seminar Title

11-11-82 Dr. F. Hares Metal Nitrosyl Complexes as Oxygen Transfer Allied Chemical Corp. Agents in the Specific Oxidation of Organic Substrates

11-12-82 Dr. H. Gorbaty Chemical and Physical Structure of Coal Exxon Research and Engineering

11-16-82 Dr. A. Gavezzotti Quantum Chemical and Force-Field Calculations University of Milan on Chemisorption

11-17-82 Dr. V. W. Weekman Catalyzing the Conversion of Photons to Mobil-Tyco Company Electrons-Photo Voltaics

12-2-82 Dr. R. A. Van Santen Chemical Bonding to Transition Metal Surfaces Shell Development Company

Reaction Oynami cs

Dr. K. Bergmann Rotational Rainbow Structure in the Na2~Rare Universitat Kaiserlautern Gas Scattering Cross Sections West Germany

6-21-82 Prof. J. P. Simons Photochemical Reaction Dynamics, Supersonic Department of Chemistry Beam Studies and Product Rotational University of Nottingham Alignment England

6-23-82 Prof. A, E. W. Knight Collisional Energy Transfer in the Ground Griffith University Electronic State of Large Polyatomics: Brisbane, Australia State Selection by Stimulated Emission Pumping

11-1-82 Prof. H. Nakamura Semiclassical Theory of Rotationally Induced Institute for Molecular Science Non-Adiabatic Transitions in Atomic Oakazaki, 444 Japan Collisions

11-2-82 Prof. F. Gianturco Proton-Molecule Inelastic Collisions as Institute of Chemical Physics Precursors of Chemical Reactions University of Rome, Italy

Electron Microscopy of Materials

Dr. D. Smith Recent Applications of the Cambridge 600kV University of Cambridge High Resolution Electron Microscope Cambridge, England

4-23-82 Dr. B. Jouffrey On Some Recent Applications of Chemical Laboratoire d'Optique Electronique Analysis by Using Characteristic Energy Centre National de la Recherche Losses Scientifique Toulouse, France

5-7-82 Dr. R* Taylor A Study of Magnetisation Processes in Dept. of Metallurgy and Imperfect Crystals by High Voltage Electron Science of Materials Microscopy University of Oxford

Dr. P. !ie*gnier Microstructure Evolution in Pt-C During Centre d'Etudes Nucleaires Electron Irradiation in HVEM de Sac I ay Saclay, France

Other Seminars Hosted

1-29-82 Or. H. Gerischer Photocurrent-Voltage Curves of Semiconductors Fritz Haber Institute Dependence on Surface Reaction Kinetics and Max Plank Gesellschaft, Berlin Resistance 286

Other Seminars Hosted (continued)

Date Speaker and Affiliation Seminar Title

11-82 Or. H. Kistenmacher Physical Property Routines in Multlcomponent Research Laboratories Linde Co. Multiphase Systems Hoellriegelskreuth, W. Germany

11-1-82 Dr. R. J. Charles Phase Equilibria in the Si0g-Al203 System G.E. Research and Development

11-2-82 Prof. F. Glanturco Proton-Molecule Inelastic Collisions as Institute of Chemical Physics Precursors of Chemical Reactions University of Rome, Italy

11-9-82 Dr. E. Hodge Why HIP (Hot Isostatic Processing)? ASEA Pressure Systems

11-17-82 Dr. E. Evleth^ Rationalization of the Structures of Rydberg Centre de Mecanique Ondulatoire Molecules Appliquee Paris, France

11-19-82 Dr. M. Datta Transpassive Dissolution of Metals Federal Institute of Technology Lausanne, Switzerland 285

Other Seminars Hosted (continued)

Date Speaker and Affiliation Seminar Title

2-16-82 Prof. J. Halpern Mechanisms and Stereochemistry of Asymetric University of Chicago Catalysis 3-82 Prof. J. Gaube Simultaneous Determination of Vapor-Liquid Chemical Engineering Department and Liquid-Liquid Equilibria Technical University of Darmstadt W. Germany

3-82 Prof. O'Donnell Distillation of Spirits Chemical Engineering Department • University College Dublin, Ireland

5-13-82 Dr. C. W. Bauschlicher Transition Metal Hydrides Polyatomics Research Institute Mountain View, California

6-82 Prof. K. Gubbins Perturbation Theories of Fluids and Fluid Chemical Engineering Department Mixtures Cornell University Ithaca, New York

*6-2-82 Dr. E. R. Davidson Theoretical Studies of Triplet State Department of Chemistry Radiative Lifetimes: Formaldehyde, University of Washington Methylene, and Sulfur Dioxide Seattle, Washington

6-16-82 Prof. J. Gerratt R-Mattix Studies of Molecular Collision University of Bristol Processes England

6-23-82 Prof. C. M. Van Baal Kinetics of Ising Alloys Technical University Delft, Netherlands

7-8-82 Dr. P. Taylor The Complete Active Space SCF Method Division of Chemical Physics Commonwealth Scientific and Industrial Research Organization Melbourne, Australia

9-12—16-82 Prof. N. Watanabe Electrochemical Application of Graphite Department of Industrial Chemistry Intercalation Compounds Containing Fluorine Sakyo-ku, Kyoto University, Japan

9-17-82 Dr. T. Sandstrom The Comparison Ellipsometer, a New Optical Chalmers University of Technology Method for the Measurement of Thin Surface Gothenburg, Sweden Films 9-24-82 Prof. J. B. Cohen The Effect of the Shape of the Phonon Northwestern University Dispersion Curve on Precipitation Reactions Evanston, Illinois in Alloys

9-28-82 Prof. D. P. Craig Dynamic Topochemistry: A Theoretical View of Research School of Chemistry Chemistry in Flexible Cages Australian National University Canberra, Australia

10-82 Ms. S. Roadcap Process Simulation at Chevron Chevron Research Co. Richmond, California

10-21-82 Dr. R. Bellows The Exxon Zir--Bromine Battery Exxon Research and Engineering Linden, New Jersey

ial Seminar 287

Appendix D

Index of Investigators

Andersen, Richard A. 195 Moore, C. Bradley 138, 229 Morris, John W., Jr. 27, 249 Bartlett, Neil 185, 195 Muetterties, Earl L. 183 Bell, Alexis T. 173, 217 Muller, Rolf H. 112, 236 Bergman, Robert G. 188 Boone, Donald H. 224, 256 Newman, John 181, 246 Bragg, Robert H. 56 Brewer, Leo 103, 226 OTander, D. R. 106

Clarke, John 87 Pask, Joseph A. 43 Colien, Marvin L. 94 Petersen, Eugene E. 217 Connick, Robert E. 172, 226, 227 Phillips, Norman E. 97 Conway, John G. 195 Pines, Alexander 124 Pitzer, Kenneth S. 141 de Fontaine, Didier 25 Prausnitz, John M. 191, 259 De Jonghe, Lutgard C. 53, 244, 264 Raymond, Kenneth N. 195 Edelstein, Norman M. 195, 251 Richards, Paul L. 73 Evans, Anthony G. 70 Ritchie, Robert 0. 39 Evans, James W. 22, 217, 242 Ross, Phillip N., Jr. 209, 238, 262

Falicov, Leo H. 91 Schaefer, Henry F., Ill 166 Finnie, Iain 66 Seaborg, Glenn T. 195 Fish, Richard H. 217 Searcy, AZan W. 45 Shen, Yuen-Ron 77 Glaeser, Andreas M. 64 Shirley, David A. 151 Gronsky, Ronald 1, 14 Somorjai, Gabor A. 115, 129, 173, 217 Harris, Charles B. 133 Streitwieser, Andrew, Jr. 195 Heinemann, Heinz 217 Hess, Dennis w. 110 Templeton, David H. 195 Thomas, Gareth 4, 14 Jeffries, Carson D. 82 Tobias, Charles W. 100, 231, Jolly, William L. 179 233, 234 Johnston, Harold S. 131 Vermeulen, Theodore 217 Kresin, Vladimir Z. 257 Vollhardt, K. Peter 176, 217 Lee, Yuan T. 160 Washburn, Jack 49 Lester, William A., Jr. 144, 255 Westroacott, Kenneth H. 11, 14, 22 Levy, Alan V. 68, 212, 217, Whittle, David P. 58, 72, 261 224, 256 Winn, John S. 136

Marrus, Richard 170 Yu, Peter Y. 85 Meyer, C. Beat 227 Miller, William H. 148 Zalkin, Alan 195

GPO 6S7-Iiq/B This report was done with support from the Department of Energy. Any conclusions or opinions expressed in this report represent solely those of the authors) and not necessarily those of The Regents of the University of California, the Lawrence Berkeley Laboratory or the Department of Energy. Reference 'o a company or product name does not imply approval or recommendation of the product by Hie University of California or (he U.S. Department of Energy to the exclusion of others that may be suitable.