Subsurface deformations in nematic liquid crystals

Abstract

The existence of subsurface deformations in a nematic liquid crystal sample of finite thickness is considered from a molecular point of view. A lattice approximation is used to take into account the intermolecular interactions responsible for the nematic phase. The analysis shows that for the Maier-Saupe interaction law the director profile is a smooth function in the whole sample. In contrast, in the framework of our simple model, for the induced-dipole--induced-dipole interaction law the director profile presents a large subsurface deformation. The results of our calculation are compared with the elastic theories for nematic liquid crystals recently proposed. In particular it is shown that the intermolecular interactions responsible for the effective splay-bend elastic constant are the origin for the subsurface discontinuity in pretilted nematic liquid crystal samples. Our predictions are obviously limited by the applicability of the na\"{\i}ve model considered in the present analysis. \textcopyright{} 1996 The American Physical Society.