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Title: Long-range orientational order, local-field anisotropy, and mean molecular polarizability in liquid crystals

Abstract

The problems on the relation of the mean effective molecular polarizability {gamma}-bar to the long-range orientational order of molecules (the optical anisotropy of the medium) in uniaxial and biaxial liquid crystals, the local anisotropy on mesoscopic scales, and the anisotropy of the Lorentz tensor L and the local-field tensor f are formulated and solved. It is demonstrated that the presence of the long-range orientational order of molecules in liquid crystals imposes limitations from below on the molecular polarizability {gamma}-bar, which differs for uniaxial and biaxial liquid crystals. The relation between the local anisotropy and the molecular polarizability {gamma}-bar is investigated for calamitic and discotic uniaxial liquid crystals consisting of lath- and disk-shaped molecules. These liquid crystals with identical macroscopic symmetry differ in the local anisotropy and the relationships between the components L{sub parallel} < L{sub perpendicular} , f{sub parallel} < f{sub perpendicular} (calamitic) and L{sub parallel} > L{sub perpendicular} , f{sub parallel} > f{sub perpendicular} (discotic) for an electric field oriented parallel and perpendicular to the director. The limitations from below and above on the molecular polarizability {gamma}-bar due to the anisotropy of the tensors L and f are established for liquid crystals of both types. These limitations indicate thatmore » the molecular polarizability {gamma}-bar depends on the phase state and the temperature. The factors responsible for the nonphysical consequences of the local-field models based on the approximation {gamma}-bar = const are revealed. The theoretical inferences are confirmed by the experimental data for a number of calamitic nematic liquid crystals with different values of birefringence and the discotic liquid crystal Col{sub ho}.« less

Authors:
 [1]
  1. Russian Academy of Sciences, Kirensky Institute of Physics, Siberian Branch (Russian Federation), E-mail: aver@iph.krasn.ru
Publication Date:
OSTI Identifier:
21246957
Resource Type:
Journal Article
Journal Name:
Journal of Experimental and Theoretical Physics
Additional Journal Information:
Journal Volume: 108; Journal Issue: 1; Other Information: DOI: 10.1134/S106377610901021X; Copyright (c) 2009 Pleiades Publishing, Ltd; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1063-7761
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANISOTROPY; APPROXIMATIONS; BIREFRINGENCE; ELECTRIC FIELDS; LIQUID CRYSTALS; MOLECULES; POLARIZABILITY; SYMMETRY; TENSORS

Citation Formats

Aver'yanov, E. M. Long-range orientational order, local-field anisotropy, and mean molecular polarizability in liquid crystals. United States: N. p., 2009. Web. doi:10.1134/S106377610901021X.
Aver'yanov, E. M. Long-range orientational order, local-field anisotropy, and mean molecular polarizability in liquid crystals. United States. doi:10.1134/S106377610901021X.
Aver'yanov, E. M. Thu . "Long-range orientational order, local-field anisotropy, and mean molecular polarizability in liquid crystals". United States. doi:10.1134/S106377610901021X.
@article{osti_21246957,
title = {Long-range orientational order, local-field anisotropy, and mean molecular polarizability in liquid crystals},
author = {Aver'yanov, E. M.},
abstractNote = {The problems on the relation of the mean effective molecular polarizability {gamma}-bar to the long-range orientational order of molecules (the optical anisotropy of the medium) in uniaxial and biaxial liquid crystals, the local anisotropy on mesoscopic scales, and the anisotropy of the Lorentz tensor L and the local-field tensor f are formulated and solved. It is demonstrated that the presence of the long-range orientational order of molecules in liquid crystals imposes limitations from below on the molecular polarizability {gamma}-bar, which differs for uniaxial and biaxial liquid crystals. The relation between the local anisotropy and the molecular polarizability {gamma}-bar is investigated for calamitic and discotic uniaxial liquid crystals consisting of lath- and disk-shaped molecules. These liquid crystals with identical macroscopic symmetry differ in the local anisotropy and the relationships between the components L{sub parallel} < L{sub perpendicular} , f{sub parallel} < f{sub perpendicular} (calamitic) and L{sub parallel} > L{sub perpendicular} , f{sub parallel} > f{sub perpendicular} (discotic) for an electric field oriented parallel and perpendicular to the director. The limitations from below and above on the molecular polarizability {gamma}-bar due to the anisotropy of the tensors L and f are established for liquid crystals of both types. These limitations indicate that the molecular polarizability {gamma}-bar depends on the phase state and the temperature. The factors responsible for the nonphysical consequences of the local-field models based on the approximation {gamma}-bar = const are revealed. The theoretical inferences are confirmed by the experimental data for a number of calamitic nematic liquid crystals with different values of birefringence and the discotic liquid crystal Col{sub ho}.},
doi = {10.1134/S106377610901021X},
journal = {Journal of Experimental and Theoretical Physics},
issn = {1063-7761},
number = 1,
volume = 108,
place = {United States},
year = {2009},
month = {1}
}