Molecular theory of flexoelectricity in nematic liquid crystals

Osipov, Mikhail; Buka, A. and Eber, N., eds. (2013) Molecular theory of flexoelectricity in nematic liquid crystals. In: Flexoelectricity in liquid crystals. World Scientific Publishing Company, pp. 9-32. ISBN 9781848168008

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Abstract

The molecular-statistical theory of flexoelectricity in nematic liquid crystals is considered in detail and general expressions for the flexoelectric coefficients are obtained in terms of the direct correlation function. These general formulae are then used to express the flexoelectric coefficients in terms of molecular model parameters using the mean-field approximation. The relation between dipolar and quadrupolar flexoelectricity is discussed in detail and the effect of molecular longitudinal and transverse electric dipoles and the polarity of the molecular shape on the value of the flexoelectric coefficients is considered. The contribution from a strong dipole–dipole intermolecular correlation is also estimated, and the dependence of the value and sign of the difference of the flexocoefficients on various molecular parameters is analysed. The results of the theory are compared with existing experimental data. Finally we consider the original version of the mean-field theory of flexoelectricity, proposed by Ferrarini, which allows us to take into account the real molecular shape.