Elasticity of thermotropic liquid crystals

摘要

In this article I describe the elasticity associated with liquid crystalline structures. The deviations from a spatially constant ground state of configurations of liquid crystals often arise due to imposition of boundary conditions, from external fields, or from thermal fluctuations. Since the characteristic distances involved in these phenomena are large compared to molecular dimensions, liquid crystals are assumed to be continuum with a set of elastic constants. I also discuss a microscopic theory involving the molecular parameters for the elastic constants. This theory which is based on the density-functional formalism, leads to expressions for the elastic constants of any system with continuous broken symmetry and are expressed in terms of the order parameters characterizing the degree and type of ordering and the pair correlation functions of an effective isotropic phase.