Numéro |
J. Phys. II France
Volume 4, Numéro 9, September 1994
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Page(s) | 1617 - 1630 | |
DOI | https://doi.org/10.1051/jp2:1994221 |
J. Phys. II France 4 (1994) 1617-1630
Elastic anomalies at the interface between a nematic liquid crystal and its vapour : a microscopic approach
Sandro Faetti and aurizio NobiliDipartimento di Fisica dell'Universita' di Pisa and Consorzio Interuniversitario di Fisica della Materia, Piazza Torricelli 2, 56100 Pisa, Italy
(Received 19 November 1993, revised 25 March 1994, accepted 18 May 1994)
Abstract
Close to the interface between a nematic liquid crystal (NLC) and another medium, the elastic constants are expected to become
functions of distance
z from the interface and of angle
between the director n and the unit vector k orthogonal to the interface. Furthermore, due to symmetry breaking, new elastic contributions that are absent in the bulk
may become important close to the interface. In this paper we consider a simple microscopic model based on van der Waals induced
dipole-induced dipole interactions under the special assumption of perfect orientational order (
S = 1). By using this model, we calculate the free energy density and the excess of surface free energy. Some elastic constants
are obtained by using a numerical procedure. In particular, a new elastic contribution which is linear in the director gradients
is obtained for the first time. Close to the interface, these elastic constants greatly depend on distance
z and are simple functions of the scalar product n
k.
© Les Editions de Physique 1994