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8 results on '"Chapuis, Gervais"'

5. The Structure of Diaqua (15-Crown-5) Copper (II) Dinitrate Described in (3+1)-Dimensional Superspace.

Author

Schönleber, Andreas and Chapuis, Gervais

Subjects
*NITRATES, *MOLECULAR structure, *COPPER, *OPTICS, *NITROGEN compounds, *INTERFEROMETRY
Abstract

Diaqua (15-crown-5) copper (II) dinitrate is an organic salt presenting an one-dimensional commensurate modulation. The diffraction pattern is characterized by strong Bragg reflections and weaker superstructure reflections (satellites). The structure is described in the superspace formalism as a modulated structure in (3+1) dimensions with occupational and displacive modulation functions. [ABSTRACT FROM AUTHOR]

Published
2004
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6. A Molecular Dynamics Study of an Incommensurate Modulation Compound: 4, 4′-Dichlorobiphenyl Sulphone.

Author

Pan, Yuansheng, Brown, David, Zuniga, F. J., and Chapuis, Gervais

Subjects
SULFONES, MOLECULAR dynamics, INTERFEROMETRY, STATICS, OPTICS, MECHANICS (Physics)
Abstract

A molecular dynamics simulation of 4, 4′-dichlorobiphenyl sulfone was carried out in order to study the phase transition from a normal to incommensurate modulated phase observed experimentally. Agreements of simulated and experimental diffraction patterns and lattice constants indicates that the simulation is able to well reproduce the normal-incommensurate phase transition. The incommensurate modulation is found to originate from large-scale fluctuations in the displacements of the molecules. [ABSTRACT FROM AUTHOR]

Published
2004
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7. Ab-initio energy calculation and X-ray diffraction in the study of the disordered N(CH3)4ClO4 structure

Author

Pinheiro, Carlos Basilio, Vianna, Reinaldo, Chapuis, Gervais, and Speziali, Nivaldo Lucio

Abstract

Single crystal X-ray diffraction in N(CH3)4ClO4 reveals two distinct sets of reflections. Neglecting the set a few and weak reflections called “satellites” a disordered structural model can be satisfactorily refined. The “satellites” can be explained by considering an orientational correlation between nearest ClO4 disordered molecules. Ab-initio energy calculation reinforce the results obtained after X-ray experiments.

Published
2001
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8. The modulated and composite model descriptions of La2Co1.7

Author

Dusek, Michal, Chapuis, Gervais, Schobinger-Papamantellos, Penelope, Wilkinson, Clive, and Petricek, Vaclav

Abstract

The crystal of chemical formula La2Co1.7 was investigated by single crystal neutron and X-ray diffraction. In the hexagonal cell, the cobalt atoms adopt a different periodicity along c, which is not commensurate with the corresponding periodicity of the La atoms. Two structure models are used to describe this behaviour, one expressing the positional modulation of cobalt by a sawtooth function and the other describing the structure as a composite system.

Published
2001
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