Abstract The nematic liquid crystal film composed of n molecular layers is studied based upon a spatially anisotropic pair potential, which reproduces approximately the elastic free energy density. On condition that the system has perfect nematic order, as in the Lebwohl—Lasher model, the director in the film is isotropic. The effect of the temperature is investigated by means of molecular field theory. Some new results are obtained. Firstly, symmetry breaking takes place when taking account of the temperature, and the state with the director along the normal of the film has the lowest free energy. Secondly, the N—I phase transition temperature increases as an effect of finite sizes instead of decreasing as in the Lebwohl—Lasher model. Thirdly, the nematic order is induced in the layers near the surface in the isotropic phase.
Received: 28 May 2004
Revised: 29 September 2004
Accepted manuscript online:
PACS:
61.30.Cz
(Molecular and microscopic models and theories of liquid crystal structure)
Fund: Project supported by the Natural Science Foundation of Hebei Province, China (Grant No 103002), and the Key Subject Construction Project of Hebei Provincial University.
Cite this article:
Zhang Zhi-Dong (张志东), Li Jing (李静), Wei Huai-Peng (魏怀鹏) Molecular field theory for nematic liquid crystal film with finite layers 2005 Chinese Physics 14 393
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