computational quantum chemistry Page 1 of 1 COMPUTATIONAL QUANTUM CHEMISTRY

This web page includes information on research carried out in the Basic Energy Sciences section of the Chemical Technology Divsion on the development of quantum chemical methods for computational thermochemistry and the application of quantum chemical methods to problems in material chemistry and chemical sciences.

Computational thermochemisty (Gaussian-2 theory, density functional theory) Molecular sieve materials Diamond thin-film growth Lithium polymer electrolytes QCf^PIX/POl Long-range electron transfer *"» "^ NOx reactions QQJ 2 k J997 For more information contact Larry Curtiss f\

e-mail: [email protected]

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http://www.cmt.anl.gov/mcp/qc.htm 8/22/97 DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or use- fulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product, process, or service by trade name, trademark, manufac- turer, or otherwise does not necessarily constitute or imply its endorsement, recom- mendation, or favoring by the United States Government or any 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. DISCLAIMER

Portions of this document may be illegible electronic image products. Images are produced from the best available original document. g2theory.htm at www.cmt.anl.gov Page 1 of 1 GAUSSIAN-2 (G2) THEORY

Gaussian-2 theory is a composite technique in which a sequence of well-defined ab initio molecular orbital calculations is performed to arrive at a total energy of a given molecular species.1 Geometries are determined using second-order Moller-Plesset perturbation theory. Correlation level calculations are done using Moller-Plesset perturbation theory up to fourth-order and with quadratic configuration interaction. Large basis sets, including multiple sets of polarization functions, are used in the correlation calculations. A series of additivity approximations makes the technique fairly widely applicable. G2 theory was originally tested on a total of 125 reaction energies, chosen because they have well-established experimental values. The test set has been expanded to include larger, more diverse molecules with enthalpies of formation at 298 K being used for comparison between experiment and theory.2 This set, referred to as the "G2 neutral test set," includes the 55 molecules whose atomization energies were used to test G2 theory and 93 new molecules. Data for this test set and a list of references are given in the web page.

• Bibliography of G2 Papers • Bibliography of Related Papers • G2 Neutral Test Set Energies • G2 Neutral Test Set Geometries • Database of G2 Energies

1. "Gaussian-2 theory for molecular energies of first- and second-row compound" L.A. Curtiss, K. Raghavachari, G. W. Trucks, and J. A. Pople, Journal of Chemical Physics 94, 7221 (1991).

2. "Assessment of Gaussian-2 and Density Functional Methods for the Computation of Enthalpies of Formation" L. A. Curtiss, K. Raghavachari, P. C. Redfern, and J. A. Pople, Journal of Chemical Physics 106, 1063 (1997).

http://www.cmt.anl.gov/mcp/g2theory.htm 9/8/97 G2BIB.HTM at www.cmt.anl.gov Page 1 of 1

This bibliography lists publications on G2 theory and variants of G2 theory.

Gaussian-2 Theory for Molecular Energies of First- and Second-Row Compounds" L. A. Curtiss, K. Raghavachari, G. W. Trucks, and J. A. Pople, Journal of Chemical Physics 94, 7221 (1991).

"Validity of Additivity Approximations Used in Gaussian-2 Theory" L. A. Curtiss, J. E. Carpenter, K. Raghavachari, and J. A. Pople, Journal of Chemical Physics 96, 9030 (1992).

"GAUSSIAN-2 Theory Using Reduced Moller-Plesset Orders" L. A. Curtiss, K. Raghavachari, and J. A. Pople, Journal of Chemical Physics 98, 1293 (1993).

"Gaussian-2 Theory: Use of Higher Level Correlation Methods, Quadratic Configuration Interaction Geometries, and Second-Order Moller-Plesset Zero-Point Energies" L. A. Curtiss, K. Raghavachari, and J. A. Pople, Journal of Chemical Physics 103,4192 (1995).

"Extension of Gaussian-2 Theory to Molecules Containing Third-Row Atoms Ga-Kr" L. A. Curtiss, M. P. McGrath, J.-P. Blaudeau, N. E. Davis,and Robert Binning, Journal of Chemical Physics 103, 6104 (1995).

"Gaussian-2 Theory: Reduced Basis Set Requirements" L. A. Curtiss, P. C. Redfern, B. J. Smith, L. Radom, Journal of Chemical Physics 104, 5148 (1996).

"Assessment of Gaussian-2 and Density Functional Methods for the Computation of Enthalpies of Formation" L. A. Curtiss, K. Raghavachari, P. C. Redfern, and J. A. Pople, Journal of Chemical Physics 106, 1063 (1997).

"Accurate Thermochemistry for Larger Molecules: Gaussian-2 Theory with Bond Separation Energies" K. Raghavachari, B. B. Stefanov, and L. A. Curtiss, Journal of Chemical Physics 106, 6764-6767 (1997).

"Investigation of the Use of B3LYP Zero-point Energies and Geometries in the Calculation of Enthlapies of Formation" L. A. Curtiss, K. Raghavachari, P. C. Redfern, and J. A. Pople, Chemical Physics Letters 270,419 (1997).

"Assessment of Modified GAUSSIAN-2 (G2) and Density Functional Theories for Molecules Containing Third-Row Atoms Ga -Kr" P. C. Redfern, L. A. Curtiss, and J.-P. Blaudeau, Journal of Physical Chemistry, in press.

"Evaluation of Bond Energies to Chemical Accuracy by Quantum Chemical Techniques" K. Ragavachari and L. A. Curtiss, in Modern Electronic Structure Theory, edited by D. R. Yarkony (World Scientific Press, Singapore, 1995) pp. 991-1021.

"Calculation of Accurate Bond Energies, Electron Affinities, and Ionization Energies" L. A. Curtiss and K. Raghavachari, in Quantum Mechanical Electronic Structure Calculations with Chemical Accuracy: Understanding Chemical Reactivity, edited by S. R. Langhoff (Kluwer Academic Press, Netherlands, 1995) pp. 139-171.

http://www.cmt.anl.gov/mcp/G2BJJB.HTM 9/8/97 G2 Test Set Energies Page 1 of 1

V G2 Neutral Test Set Energies

Reference: Assessment of Gaussian-2 and Density Functional Methods for the Computation of Enthalpies of Formation, L. A. Curtiss, K. Raghavachari, P. C. Redfern, and J. A. Pople, Journal of Chemical Physics, 106, 1063 (1997).

G2, G2(MP2), G2(MP2,SVP)

• Ee energies, Eo energies, H298 energies • AHf (0 K). AH/Y298 K) • Deviation with experiment • Atom energies

Density functional theory: SVWN, B-P86, B-PW91, B-LYP, B3-P86, B3-PW91, B3-LYP

• AH/fO K). AH/Y298 K) • Deviation with experiment

http://www.cmt.anl.gov/mcp/G2set.HTM 9/8/97 G2 geometries Page 1 of 5

G2 Neutral Test Set Geometries

This page contains MP2(full)/6-31G* geometries for the 148 neutral molecules in the G2 test set. Each entry contains a model of the molecule which can be rotated. The geometries are also available as a single file by anonymous FTP from axp.cmt.anl.gov. The file is located in the directory g2testsets. [Reference: L. A. Curtiss, K. Raghavachari, P. C. Redfern, and J. A. Pople, J. Chem. Phys. Vol. 106 1063 (1997)]

Molecule JH (Lithium hydride) BeH CH

CH, CH, NH NHc NHc OH OHC FH

SiH, PHc PH. SHc CIH

LiF

CN http://www.cmt.anl.gov/mcp/g2geoma.htm 9/8/97 G2 geometries Page 2 of 5

HCN CO HCO H2CO

H2NNH: NO

HOOH

>Or

Nac

Sl2 E2

NJaCI SiO SC SO CIO FCI

HOCI SO. BFc

COS

JOFr SiF, SiCL

UNO http://www.cmt.anl.gov/mcp/g2geoma.htm 9/8/97 G2 geometries Page 3 of 5

UNI--:

CIFc

c2ci4 CFoCN CHoCCH (propyne)

CH2=C=CH2 (aliene) (cvclopropene)

CH3CH=CH2 (proovlene) 1 C3H6 (cyclopropane )

C3H8 (propane) CHoCHCHCHo (butadiene)

O,H6 (2-butvne) (methylene cvciopropane) (bicyclobutane)

C/[H6 (cyclobutene) C^Hg (cyclobutane) (isobutene) (trans butane) (isobutane)

C5H8 (spiropentane) (benzene)

CHF,

(methylamine) oCN (methyl cyanide)

)H3NO2 (nitromethane) QNQ (methyl nitrite) (methyl silane) HCOOH (formic acid) HCOOCHo (methyl formate) /H0CONH0 (acetamide) (aziridine) NCCN (cyanogen) http://www.cmt.anl.gov/mcp/g2geoma.htm 9/8/97 G2 geometries Page 4 of 5

CHoCHoNHo (trans ethvlamine) CHoCO (ketene) 021-1^0 (oxirane) CHQCHO (acetaldehvde) HCOCOH (qlvoxal) H3CH0OH (ethanol) (dimethvlether) (thiirane)

(CH3)2SQ (dimethyl sulfoxide)

C2H5SH (ethanethioi)

)H3SCH3 (dimethyl sulfide)

CH2=CHF (vinyl fluoride) (ethyl chloride) 'Ho=CHCI (vinyl chloride)

H2=CHCN (acrvlonitrile) (acetone) IHQCOOH (acetic acid) (acetvl fluoride) (acetvl chloride)

:H3CH2CH2CI (propyl chloride)

(CH3)2CHOH (isopropanol)

CoH5OCH3 (methyl ethyl ether) (trimethylamine)

)4id40iluran) (thiophene) (pyrrole) (pyridine)

D2 HS CCH

)H30 CS (i

)H3CH2O (2

(CH3)2CH (^A'

CH3)3C (t-butvl radical) http://www.cmt.anl.gov/mcp/g2geoma.htm 9/8/97 G2 geometries Page 5 of 5

http://www.cmt.anl.gov/mcp/g2geoma.htm 9/8/97 Molecular Sieve Materk Page 1 of 2

S. A. Zygmunt, L. A. Curtiss, and L. E. Iton

Argonne National Laboratory

This theoretical research program seeks to better understand chemical reactions arising from acid catalysis in a family of catalytic materials called zeolites.

Zeolites are aluminosilicates which have a very porous structure consisting of cavities and channels through which molecules of the right size and shape may readily diffuse. Below is a wireframe representation of the structure of the zeolite ZSM-5, where the tetrahedral (silicon or aluminum) atoms sit at the vertices and the red wires represent Si-O-Si or Si-O-Al linkages. The dotted blue lines show the boundaries of the unit cells.

The unique and useful catalytic properties of zeolites result from the presence of Bronsted acid sites in the interior. Where an aluminum atom replaces a silicon atom in the zeolite framework, a charge-balancing cation is required to preserve overall charge neutrality. When the cation is a proton, the zeolite can be a proton donor, or Bronsted acid, and can catalyze a wide range of industrially useful chemical reactions.

Our research involves the use of high-level computational quantum mechanics to calculate the stable equilibrium structures of complexes formed when small molecules adsorb at the acid site in zeolites. We also seek to locate the unstable equilibium structures resulting from the transfer of the proton from the zeolite framework to the adsorbed molecule. The process of proton transfer is a key step in all acid catalyzed reactions, and yet it is poorly understood at an atomic level. A knowledge of the http://www.cmt.anl.gov/mcp/zeoiite.htm 8/19/97 Molecular Sieve Materials Page 2 of 2

energies of these various structures yields predictions of the potential energy barriers for the reactions, and this in turn gives information about the reaction rates.

For example, the structures at the right show two possible complexes arising from the interaction of a water molecule with the acid site in the zeolite H-ZSM-5. On the right, the water is hydrogen-bonded to the acid site and the adjacent oxygen atom, while on the left the acidic proton has been transferred to the adsorbed water, + forming a hydronium ion (H3O ). Our calculations show that the complex on the right is the true stable equilibrium structure, while the one on the left represents an unstable equilibrium, or transition state structure.

"Computational Studies of Water Adsorption in Zeolites," S. A. Zygmunt, L. A. Curtiss, and L. E. Iton, Zeolites: A Refined Tool for Designing Catalytic Sites, L. Bonnevoit and S. Kaliaguione, Eds (Elsevier Science, 1995),pp. 101-107. "Computational Studies of Bronsted Acid Sites in Zeolites," L. A. Curtiss, L. E. Iton, and S. A. Zygmunt, High Performance Computing 1995proceeding of the 1995 Simulation Multiconference.The Society for Computer Simulation, April 9-13, 1995 Phoenix, AZpp. 111-115.

"Computational Studies of Water Adsorption in the Zeolite H-ZSM-5" S. A. Zygmunt, L. A. Curtiss, and L. E. Iton, Journal of Physical Chemistry, 100 , 6663 (1996).

"Evidence for Dimeric and Tetrameric Water Clusters in HZSM-5," D. H. Olson, S. A. Zygmunt, M. K. Erhardt, L. A. Curtiss, Zeolites, 18, 347 (1997).

http://www.cmt.anl.gov/mcp/zeolite.htm 8/19/97 thin-film growth Page 1 of 2

Diamond Film Growth from Buckyball Precursors

Larry Curtiss, David Homer, Paul Redfern, and Dieter Gruen

Argonne National Laboratory, Argonne, Illinois 60439

The practical utility and unique properties of diamond films have produced a great deal of interest in the synthesis of diamond films by chemical vapor deposition (CVD). In most cases growth is initiated by the dissociation of a gaseous mixture of H2 and a simple hydrocarbon precursor such as CH4. Recently, extremely smooth (-30 nm rms roughness) diamond films have been grown in experiments at Argonne National Laboratory involving chemical vapor deposition following fragmentation of buckyball, C60, in a microwave discharge, both with and without the addition of hydrogen. The C2 molecule, produced in large amounts in the fragmentation of C60, has been proposed as the principal growth species, with diamond growth occurring by insertion of C2 into the C-H bonds of the hydrogen-terminated diamond surface. A possible mechanism for growth of diamond thin-films based on C2 as the growth species using computational quantum chemical methods has been carried out. This study has employed large cluster models for the diamond surface and required use of the supercomputing facilities at NERSC. The reaction energies and energy barriers for postulated steps in a mechanism, based on addition of C2 to adjacent sites on a diamond (110) surface, were investigated. The model of the surface used is illustrated in the attached figure. The addition of a C2 to the trough in the hydrogen terminated surface is energetically very favorable, with energy lowerings of about 160 kcal per mole of C2. The energy barriers for addition of C2 to the surface are small. Adjacent C2 moieties on the surface, adsorbed in ethylene-like arrangements, can be connected via a radical mechanism involving initiation by hydrogen atom addition to the double bond of one ethylene-like group or by a mechanism involving no hydrogen. Our results suggest that there is little or no energy barrier for either reaction. The completion of a new surface layer via formation of single bonds between the radical structure and ethylene-like adsorbates results in an energy lowering of about 40-50 kcal per mole of C-C bonds. This growth mechanism is unique in that it does not require hydrogen and may be responsible for the extremely smooth diamond films produced from buckyballs.

1. "A Theoretical Study of the Energetics of Insertionof Dicarbon (C2) and Vinylidene into Methane C-H Bonds," D. A. Homer, L. A. Curtiss, and D. M. Gruen, Chemical Physics Letters 233, 243 (1995).

2. "Theoretical Studies of Growth of Diamond (110) from Dicarbon." P. Redfern, D. A. Homer, L. A. Curtiss, and D. M. Gruen, Journal of Physical Chemistry 100, 11654 (1996).

http://www.cmt.anl.gov/mcp/diamond.htm 8/19/97 thin-film growth Page 2 of 2

Cluster model of the (110) diamond surface showing the trough where the C2 dimers adji to form new diamond surface

http://www.cmt.anl.gov/mcp/diamond.htm 8/19/97 lithium polymer electrolytes Page 1 of 2

Electronic Structure Calculations on Lithium Polymer Electrolytes

L. A. Curtiss

Chemical Technology Division, Argonne National Laboratory

This project involves a fundamental study of lithium polymer electrolytes used in lithium battery systems. Ionically conducting polymers were first discovered about 20 years ago and were subsequently used as electrolytes in solid-state batteries. Ion-conducting polymers are solutions of salts in polymers in which a macroscopically solid state is achieved by entanglement or cross-linking. Microscopically they behave as liquids. The polymer electrolytes are generally composites of a polyethylene oxide and a salt such as LiC104, LiAsF6, or LiCF3SO3. It is generally believed that ionic conduction is a property of the amorphous phase and that ion association, ion-polymer interactions, and local relaxations of the polymer strongly influence the ionic mobility. However much about the nature of the ion association processes, and the ion-polymer interactions and the role that they play in ionic conductivity of the electrolytes remains unknown. In this effort we are investigating the effects of the polymer host on ion solvation and the attendant effects of ion pairing, which strongly affect the ionic transport in these systems. The experimental part involves neutron scattering measurements and x-ray scattering measurements. The theoretical part involves electronic structure calculations using ab initio molecular orbital theory to investigate energetic, structural, and dynamical properties of ion-ion and ion-polymer interactions at a molecular level in combination with molecular dynamics simulations being carried out at the University of Minnesota. Information gained from this study will be used to help improve the performance of lithium battery systems

In the theoretical work the polymer is being modeled using small alkyl oxides such as diethyl ether and diglyme.1 The interaction of a lithium cation with the oxygens are being investigated and the potential energy surfaces are being calculated to obtain potentials that are being used in molecular dynamics simulations.2 The calculations are used to examine the stability of different coordinations of lithium with the polymer model and barriers to migration of the lithium cation from one coordination site to another coordination site. The barriers for transfer of lithium cation are very important in understanding the transport mechanism in the polymer electrolyte. The results of the calculations will be used in helping to interpret new experimental measurements on lithium polymer electrolytes.In the past year we have investigated the potential energy surfaces of Li+-diglyme and Li +-triglyme complexes, which are models for polyethylene oxide electrolytes. Eighteen local minima were located that correspond to coordination of Li+ with one to four oxygens. The binding energies of the complexes increase with coordination of the Li+ by oxygen, although the binding per Li-0 bond decreases. The potential energy surfaces for lithium cation migration between one- and two-coordination sites and two- and three-coordination sites in the Li+-diglyme complexes were investigated and five transition states were located. While the barriers are small (less than 2 kcal/mol) for lithium cation migration from lower to higher coordination, the barriers are large (20-30 kcal/mol) for higher to lower coordination. The latter corresponds to the barrier for transfer of Li+ from one end of diglyme to the other and is approximately the difference in binding energy of the higher and lower coordination structures.

http://www.cmt.anl.gov/mcp/lipeo.htm 8/19/97 lithium polymer electrolytes Page 2 of 2

1. "Lithium Ion Transport in a Model of Amorphous Polyethylene Oxide," P. T.Boinske, L. A. Curtiss, J. W. Halley, B. Lin, andA. Sutjianto, Journal of Computer-Aided Materials Design 3, 385-402(1996).

2. "Theoretical Study of the Potential Energy Surface of Diglyme A. Sujianto and L. A. Curtiss, Chemical Physics Letters, 264, 127-133 (1997).

Coordination of the lithium cation by two (left) and five (right) oxygens of a polyethylene oxide chain as calculated from ab initio molecular orbital theory.

http://www.cmt.anl.gov/mcp/lipeo.htm 8/19/97 electron transfer Page 1 of 2

Long-Distance Electronic Coupling in Donor/Acceptor Molecules

L.A. Curtiss and J.R. Miller

Argonne National Laboratory, Argonne, IL Electron transfer processes involving organic molecules are relevant to many biological systems, such as photosynthesis. As a result electron transfer is being studied in detail, both theoretically and experimentally. One of the key issues in the field is the mechanism of long-range electron transfer, that is how the electronic coupling of donor and acceptor sites is mediated by the intervening material between the donor and acceptor. However, the electronic coupling interaction between a donor and acceptor is still one of the least understood aspects of charge transfer reactions. In most intramolecular electron transfer reactions, this coupling interaction is presumed to occur primarily through the bonds of the spacer that tethers the donor and acceptor. Since this is an important source of coupling, it is useful to understand how this interaction occurs, including the magnitude of the effect, and to understand the reasons for the behavior.

In present work, we are investigating the dependence that coupling has on spacer structure by addressing the question of how the coupling is dependent on the bond angles of the spacer and by determining the magnitude of this effect. Both electron transfer and hole transfer rates were measured for a series of compounds and compared with results from computations being carried out on the supercomputers available at NERSC. With these results, we can test the limits of our current computational methods and use our computational results to understand the coupling mechanism and explain the observed effect. The calculation of accurate magnitudes of the couplings requires a high level of theory. Our compuations are giving new insights into the controlling factors of electron tranfer. An example is given in the attached figure, which shows a breakdown of electron transfer pathways in two of the compounds that have been studied experimentally and theoretically. The calculations indicate that the trans arrangement of the bonds provides for superior transmission of electronic coupling due to constructive interference between principal pathways, while in the cis or gauche arrangements destructive interference leads to poorer electronic coupling.

1. "An Investigation of Through-Bond Coupling Dependence on Spacer Structure," B. P. Paulson, L. A. Curtiss, B. Bal, G. L. Closs,and J. R. Miller, Journal of the American Chemical Society 118, 378 (1996).

2. "Electron Binding Energy and Long-Range Electtronic Coupling. A Theoretical Study," B. Sengupta, L. A. Curtiss, J. R. Miller, Journal of Chemical Physics 104, 9888 (1996).

http://www.cmt.anl.gov/mcp/et.htm 9/8/97 electron transfer Page 2 of 2

Dimethylenebicyclooctane

Dimethyienecyclohexane

Illustration of Different Types of Electron Transfer Pathways Found in Two Donor-Acceptor Systems Having Five-Bond Space

http://www.cmt.anl.gov/mcp/et.htm 9/8/97 nox reactions Page 1 of 1

V

Computational Studies of NOX Reactions in Waste Storage

A. R. Cook, L. A. Curtiss, D. Meisel, and J. R. Miller

Argonne National Laboratory

In this project we are carrying out high level ab initio molecular orbital calculations of reaction pathways of NOx reactions that may be occurring in nuclear waste storage tanks. The computations will be used to calculate equilibrium structures of reactants and products of oxidizing NOx radical anions in order to determine free energies for possible reactions. In addition, activation energies will be calculated for transition states to help determine rates for the reactions. The methods used in these calculations include Gaussian-2 (G2) theory which has been shown to provide accurate reaction energies. In some cases the energetics will be measurable by uniquely-capable pulse radiolysis experiments, while in others computation will provide the only known determinations. Theory and experiment will be closely coupled. We will also use density functional theory for very large systems which are too large to address with G2 theory. Solvation effects will be included using contiuum models.

This is a new project; we will add a description of our progress as it becomes available.

http://www.cmt.anl.gov/mcp/NOx.htm 8/19/97