|Title:||Orientation-translation and orientation-orientation correlations in neopentane plastic crystals : computer simulation|
|Authors :||Depondt, Philippe|
|Published in :||Molecular Physics : an International Journal at the Interface Between Chemistry and Physics|
|Publisher / Ed. Institution :||Taylor & Francis|
|License (according to publishing contract) :||Licence according to publishing contract|
|Type of review:||Peer review (Publication)|
|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|
|Appears in Collections:||Publikationen School of Engineering|
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