Induced Nearest-Neighbor Bond Orientational Ordering and Structural Transformation in a Two-Dimensional Liquid Crystal Model

Abstract

The intermolecular pair potential responsible for orientational phase transitions in liquid crystal materials are anisotropic and depend on both the orientation of the molecules and on the orientation of the intermolecular vector which connects interacting particles. The induced nearest-neighbor hexatic bond orientational order present in two-dimensional liquid crystalline systems originates from the couplings between the molecular and the intermolecular bond orientation. We show, using an anistropic van der Waals pair potential, that the degree of bond orientational order increases when the strength of these coupling terms is increased. We find that such an increase results in a structural transformation of the nearest-neighbor shell which is similar to the structural phase transitions predicted from zero temperature lattice calculations. Connections are made between the behavior exhibited by the pair potential we study and the behavior of freely-suspended smectic liquid crystal films.