Rotational dynamics of simple asymmetric molecules

D. Fragiadakis and C. M. Roland
Phys. Rev. E 91, 022310 – Published 24 February 2015

Abstract

Molecular dynamic simulations were carried out on rigid diatomic molecules, which exhibit both α (structural) and β (secondary) dynamics. The relaxation scenarios range from onset behavior, in which a distinct α process emerges on cooling, to merging behavior, associated with two relaxation peaks that converge at higher temperature. These properties, as well as the manifestation of the β peak as an excess wing, depend not only on thermodynamic conditions, but also on both the symmetry of the molecule and the correlation function (odd or even) used to analyze its dynamics. These observations help to reconcile divergent results obtained from different experiments. For example, the β process is more intense and the α-relaxation peak is narrower in dielectric relaxation spectra than in dynamic light scattering or NMR measurements. In the simulations herein, this follows from the weaker contribution of the secondary relaxation to even-order correlation functions, related to the magnitude of the relevant angular jumps.

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  • Received 11 September 2014
  • Revised 9 January 2015

DOI:https://doi.org/10.1103/PhysRevE.91.022310

Published by the American Physical Society

Authors & Affiliations

D. Fragiadakis and C. M. Roland

  • Naval Research Laboratory, Chemistry Division, Code 6120, Washington DC 20375-5342, USA

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Issue

Vol. 91, Iss. 2 — February 2015

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