Title: Orientation-translation and orientation-orientation correlations in neopentane plastic crystals : computer simulation
Authors : Depondt, Philippe
Breymann, Wolfgang
Published in : Molecular Physics : an International Journal at the Interface Between Chemistry and Physics
Volume(Issue) : 87
Issue : 5
Pages : 1015
Pages to: 1037
Publisher / Ed. Institution : Taylor & Francis
Issue Date: 1996
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (Publication)
Language : English
Subject (DDC) : 530: Physics
Abstract: The dynamics of orientationally disordered crystals, such as neopentane C(CH3)4, couple translational and orientational variables in a complex way. From the results of a molecular dynamics simulation of the orientationally disordered phase of neopentane, simple geometrical methods are used to define functions that can be displayed on a two-dimensional surface and yield practical information, and from these are obtained the single-molecule orientation-translation coupling, the coupling between the translation of a molecule and the orientation of one of its neighbours, and the orientation-orientation coupling of two neighbouring molecules. The single-molecule orientation-translation term, although weak, is consistent with experimental results. A distinct orientation-orientation coupling is visible when a C-C bond of one molecule points at a neighbouring molecule, while a bond of that neighbour points away from the former. Isotropy around the connecting vector tends to disqualify pseudospin-type models for neopentane. The most salient feature, however, is the strong two-molecule orientation-translation correlation, which confirms the motion of one molecule when a C-C bond of one of its neighbours points in its direction; up to now this was only inferred from partial experimental data. Predictions are made for the type of information that is likely to be obtained from neutron diffuse scattering.
Departement: School of Engineering
Organisational Unit: Institute of Data Analysis and Process Design (IDP)
Publication type: Article in scientific Journal
DOI : 10.1080/00268979600100701
ISSN: 0026-8976
URI: https://digitalcollection.zhaw.ch/handle/11475/4621
Appears in Collections:Publikationen School of Engineering

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