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Front cover: The field induced magnetic soliton in GuGeC>3 and the associated structural distortion (see section 2.2.1. of this report). Back cover: AFM image of the worn surface of carbon fibre reinforced PEEK (see section 2.8.24. of this report). Ris0-R-1156(EN) Annual Progress Report of the Condensed Matter Physics and Chemistry Department 1 January - 31 December 1999 Edited by B. Lebech Rise National Laboratory, Roskilde, Denmark February 2000 Abstract The Condensed Matter Physics and Chemistry Department is concerned with both fundamental and ap- plied research into the physical and chemical properties of materials. The principal activities in the year 1999 are presented in this progress report. The research in physics is concentrated on neutron and X-ray scattering techniques and the problems studied include two- and three-dimensional structures, magnetic ordering and spin dynamics, supercon- ductivity, phase transitions and nano-scale structures. The research in chemistry includes chemical syn- thesis and physico-chemical investigation of small molecules and polymers, with emphasis on polymers with new optical properties, block copolymers, surface-modified polymers and supramolecular struc- tures. Theoretical work related to these problems is undertaken, including Monte Carlo simulation, com- puter simulation of molecules and polymers and methods of data analysis. The readers are invited to contact the department or the authors of the individual contributions for more detailed information than can be given in this report. The postal address is: Condensed Matter Physics and Chemistry Department, Ris0 National Laboratory. P.O. Box 49, DK-4000 Roskilde, Denmark. E- mail addresses may be found one the last pages of this report or under the titles of the contributions. This report contains unpublished results and should not be quoted without permission from the authors. Front cover illustration: The field induced magnetic soliton in GuGeO3 and the associated structural distortion (see section 2.2.1. of this report). Back cover illustration: AFM image of the worn surface of carbon fibre reinforced PEEK (see section 2.8.24. of this report). ISBN 87-550-2647-8; 87-550-2648-6 (Internet) ISSN 0106-2840 ISSN 1397-8985 Information Service Department-Ris0-2OOO Table of contents 1. INTRODUCTION 7 2. RESEARCH PROJECTS IN THE DEPARTMENT 9 2.1. Theory 11 2.1.1. Computer simulation of the phase diagram for the extended AS YNNNI model 11 2.1.2. Field dependence of the n resonance in high-rc superconductors: An SO(5)-based prediction 12 2.1.3. Simulation of magnetic properties of small antiferromagnetic particles 13 2.1.4. RLexact, a general program for exact diagonalisation of quantum spin systems 14 2.1.5. Mesoscopic simulation of polymers 15 2.1.6. Simple model for the anomalous large volume expansion of polypyrrole 16 2.1.7. Tuning the laser wavelength in azobenzene-based data storage materials by ab initio quantum chemical calculations 17 2.1.8. Optical properties of large molecules as calculated by an electrostatic interaction model ..18 2.1.9. Accurate intermolecular potentials: Bridging the gap between quantum chemistry and molecular simulations 19 2.1.10. Molecular dynamics simulation of incoherent neutron scattering experiments of water near macromolecules 20 2.1.11. Modelling scattering experiments of polymers by the Kratky-Porod model 21 2.1.12. Lattice models for protein folding 22 2.1.13. Secondary structures from hydrogen bonds in polymer folding 22 2.2. Magnetisme 23 2.2.1. Neutron scattering study of the field-induced soliton lattice in CuGeO3 23 2.2.2. Neutron scattering study of the excitation spectrum in the high-field phase of CuGeO3 24 2.2.3. Finite temperature excitation spectrum of the 2D S=l/2 Heisenberg antiferromagnet CFTD 25 2.2.4. Magnetic ordering in HoD2+xthin films 26 2.2.5. Magnetic ordering of TbRu2Si2 at low temperatures 27 2.2.6. Magnetic fluctuations in maghemite nano-particles 28 2.2.7. Small angle neutron scattering from cubic a-Fe nanoparticles 29 2.2.8. Powder neutron diffraction studies of UAI3C3 30 2.3. Superconducting materials and phenomena 31 2.3.1. Anomalous tetragonal symmetry of a superconducting YBa2Cu306.62 single crystal: I: Magneto-optic studies of superconductivity 31 2.3.2. Anomalous tetragonal symmetry of a superconducting YBa2Cu306.62 single crystal: II: Studies of the tetragonal structure 32 2.3.3. Charge density studies of YBa2Cu3O6.98 33 2.3.4. Spin dynamics of PrBa2Cu3062 34 2.3.5. Two coexisting oxygen configurations in non-superconducting NdBa2Cu3O65 35 2.3.6. Flux line lattice reorientation transition in LuNi2B2C with i7|| a 36 2.3.7. Magnetic structures in the superconducting state of TmNi2B2C 37 2.3.8. Characterisation of BiSCCO/Ag superconducting tapes 38 2.3.9. In-situ study of individual grains in superconducting BSCCO/Ag tapes using the 3D XRD microscope 39 2.3.10. Magneto-optical investigations of multifilamentary Bi-2223 tapes 40 2.4. Structure and defects 41 2.4.1. Evaluation of the solid state dipole moment and pyroelectric coefficient of phosphangulene by multipolar modelling of x-ray structure factors 41 2.4.2. The structure of Zn2F(PO4) - A neutron powder diffraction study 42 2.4.3. Zinc substitution in ZnAPO-35 - A neutron powder diffraction study 43 Ris0-R-1156(EN) 2.4.4. Strontium oxalate hydrate — A neutron powder diffraction study 44 2.4.5. The structural role of iron in tetrahedrite Cui2-xFexSb4Si3 and tennatite Cui2-xFexAs4Si3by means of neutron diffraction 45 2.4.6. X-ray powder diffraction on cubic Fe nanoparticles 46 2.5. Structure and interfaces 47 2.5.1. X-ray reflectivity measurements on plasma activated bonded wafers 47 2.5.2. Bonded Si wafers with small and large twist angles 48 2.5.3. The Interface of directly bonded Si wafers with a finite tilt angle 49 2.5.4. Surface structures of Cu3Au and Au3Cu determined by surface x-ray diffraction 50 2.5.5. High-index semiconductor surfaces: Structure determination of a Si(l 15) surface reconstruction 51 2.5.6. Periodically arranged dislocation lines in MgO films grown on Ag(100) 52 2.5.7. Structural studies of the reconstructed Pb/InAs(001) surface 53 2.5.8. Nanoscale quasi-one-dimensional quantum structures induced by adsorbates: Structural study of the Si( 111 )-(8x2)-In low temperature reconstruction 54 2.5.9. X-ray diffraction studies on metal-rich (001) surfaces of III-V compound semiconductors 55 2.5.10. Structural study of the commensurate-incommensurate low temperature phase transition of Pb on Si(l 11) 56 2.5.11. Dehydration of aluminium hydroxides studied by in situ small and wide angle x-ray scattering 57 2.5.12. Particle size distribution of an Ni/SiO2 catalyst determined by ASAXS 58 2.5.13. Nano-dispersed NiMo/Al2O3 catalysts studied by ASAXS 59 2.5.14. Spontaneous chiral separation on solid mineral surfaces 60 2.5.15. Building better plastic transistors: Study of orientation effects in self-organised domains of thin polymer films 61 2.5.16. Our new versatile TOF-SIMS instrument 62 2.5.17. Plasma oxidation of silicones 63 2.5.18. Wet cleaning of silicon wafers 64 2.5.19. Surface morphology of PS-PDMS diblock copolymer films 65 2.5.20. Injection moulding nanostructures 66 2.5.21. Monitoring protein adsorption kinetics by In-Situ ellipsometry 67 2.5.22. Protein repellent surface modification of silicon and PDMS 68 2.6. Langmuir films 69 2.6.1. Structure of Langmuir films of conjugated disk-like molecules studied by synchrotron X-ray diffraction 69 2.6.2. Langmuir films of self-complementary hydrogen bonded disk molecules 70 2.6.3. GIXD Investigation of a Conjugated Cyclomer at the Air-Water Interface 71 2.6.4. Lipase adsorption at the air/water interface and the crystallographic phase problem for X-ray reflectivity 72 2.6.5. Lipid-lipase interactions investigated using synchrotron x-ray scattering 73 2.6.6. Monolayer structures of triple-chain phosphatidylcholines as substrates for phospholipases 74 2.6.7. Cardiolipin: A four-chain phospholipid coupled to the charged polyelectrolyte PDADMAC 75 2.6.8. X-ray and neutron reflectivity from surface monolayers of a lipopolymer 76 2.6.9. Phospholipid headgroup organization of DMPA in Langmuir monolayers 77 2.6.10. Bacterial S-layer protein coupling to lipids: Combination of x-ray and neutron reflectivity measurements for a detailed assessment of the protein/lipid interface 78 2.6.11. Towards spontaneous generation of enantiomerically pure peptides via polycondensation of racemic precursors at the air-water interface 79 2.6.12. 2D-crystalline films of Cd2+and Pb2+ salts of rigid-rod molecular wires aligned parallel to the air-water interface 80 Ris0-R-1156(EN) 2.6.13. Self-assembly into 2D-crystalline monolayers of molecules adopting an m-shape on the surface of water 81 2.6.14. Self-assembled monolayers of folded molecules on the surface of water 82 2.7. Microemulsions, surfactants and biological systems 83 2.7.1. Interaction of P-lactoglobulin and aggregates of phosphorlipids 83 2.7.2. Solutions with a crystallization agent investigated by the SANS technique 84 2.7.3. Droplet polydispersity and shape fluctutions in AOT microemulsions studied by contrast variation small-angle neutron scattering 85 2.7.4. A small-angle neutron scattering (SANS) study of surfactant aggregates formed in aqueous mixtures of sodium dodecyl sulfate (SDS) and didodecyldimethylammonium bromide (DDAB) 86 2.7.5. A small-angle neutron scattering (SANS) study of surfactant micelles formed in aqueous mixtures of sodium dodecyl sulfate (SDS) and tetraethylenoxidedodecylamid (TEDAD) 87 2.7.6.

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