DOI: 10.1051/jp2:1994215
J. Phys. II France 4 (1994) 1519-1540

Interfacial energy for nematic liquid crystals : beyond the spherical approximation

G. Barbero^{1, 2}, L. R. Evangelista^{1, 3}, M. Giocondo² and S. Ponti<sup>1

1</sup>  Dipartimento di Fisica del Politecnico, Corso Duca Degli Abruzzi 24, 10129 Torino, Italy
²  Dipartimento di Fisica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy
³  Universidade Estadual de Maringá, Avenida Colombo 3690, 87020-900 Maringá Paraná, Brazil

(Received 3 March 1994, revised 25 April 1994, accepted 9 June 1994)

Abstract
By means of a simple pseudomolecular model the surface elastic properties of nematic liquid crystals are analysed. We show that in the Maier-Saupe approximation for the intermolecular interaction and supposing the interaction volume of ellipsoidal shape, the bulk elastic constants of splay and twist are expected to be equal and different from the bend one. The dependence of the bulk elastic constants on the eccentricity of the ellipsoid is studied. In the same framework it is shown that the number of phenomenological parameters necessary to describe the surface elastic behaviour of nematic liquid crystals is different from the one in the bulk. The position dependence of the surface elastic constants is evaluated and the anisotropic part of the surface tension is determined. The anchoring energy strength, in the Rapini-Papoular sense, versus the eccentricity of the ellipsoid representing the interaction volume is also estimated.

© Les Editions de Physique 1994