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Determination of the Maier-Saupe strength parameter from dielectric relaxation experiments: a molecular dynamics simulation study

Determination of the Maier-Saupe strength parameter from dielectric relaxation experiments: a molecular dynamics simulation study
Determination of the Maier-Saupe strength parameter from dielectric relaxation experiments: a molecular dynamics simulation study
Molecular dynamics simulations have been performed to investigate the rotational motion in the nematic and isotropic phases of a model mesogenic system in which the interactions between the molecules are represented by the Gay-Berne potential. First-rank end-over-end rotational relaxation times, analogous to those measured using dielectric relaxation spectroscopy for real mesogens with a longitudinal electric dipole, have been determined as a function of temperature and density. The relaxation times at temperatures throughout the nematic region are found to be larger than the values extrapolated from the isotropic phase to the same temperature. The simulation results are compared with the extended Debye theory for dielectric relaxation in the nematic phase. This relates the reduction in the relaxation rate to the retardation factor which depends on the Maier-Saupe strength parameter, and in turn is defined uniquely by the second-rank orientational order parameter. The simulations indicate that the retardation factor at constant strength parameter is density dependent, a feature neglected in the relaxation theory. We compare the simulation results where possible with experiment.
high-pressure, computer-simulation, anisotropic systems, order-parameter, liquid-crystals, phase
0026-8976
1365-1371
Bates, Martin A.
6001a185-ebdb-4ed1-959c-6bba80c61ed2
Luckhurst, Geoffrey R.
7807d1c6-54a1-414f-9abe-22de4d9c30f7
Bates, Martin A.
6001a185-ebdb-4ed1-959c-6bba80c61ed2
Luckhurst, Geoffrey R.
7807d1c6-54a1-414f-9abe-22de4d9c30f7

Bates, Martin A. and Luckhurst, Geoffrey R. (2001) Determination of the Maier-Saupe strength parameter from dielectric relaxation experiments: a molecular dynamics simulation study. Molecular Physics, 99 (16), 1365-1371. (doi:10.1080/00268970110061829).

Record type: Article

Abstract

Molecular dynamics simulations have been performed to investigate the rotational motion in the nematic and isotropic phases of a model mesogenic system in which the interactions between the molecules are represented by the Gay-Berne potential. First-rank end-over-end rotational relaxation times, analogous to those measured using dielectric relaxation spectroscopy for real mesogens with a longitudinal electric dipole, have been determined as a function of temperature and density. The relaxation times at temperatures throughout the nematic region are found to be larger than the values extrapolated from the isotropic phase to the same temperature. The simulation results are compared with the extended Debye theory for dielectric relaxation in the nematic phase. This relates the reduction in the relaxation rate to the retardation factor which depends on the Maier-Saupe strength parameter, and in turn is defined uniquely by the second-rank orientational order parameter. The simulations indicate that the retardation factor at constant strength parameter is density dependent, a feature neglected in the relaxation theory. We compare the simulation results where possible with experiment.

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More information

Published date: 2001
Keywords: high-pressure, computer-simulation, anisotropic systems, order-parameter, liquid-crystals, phase

Identifiers

Local EPrints ID: 19399
URI: https://eprints.soton.ac.uk/id/eprint/19399
ISSN: 0026-8976
PURE UUID: fe1e212d-a49f-40ba-9846-39029e234d30

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Date deposited: 14 Feb 2006
Last modified: 15 Jul 2019 19:27

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