A two-ellipsoid model based upon a Gaussian overlap potential

Abstract

The two-ellipsoid model (TEM) is proposed as a versatile single-site model which can be used in the study of liquid crystal phases. This TEM uses two ellipsoids to describe a molecule, one ellipsoid for the geometry and the other for the interaction strengths of the molecule. The present TEM can mimic asymmetric interactions of a liquid crystal molecule by separating the center of the interaction ellipsoid from that of the geometry ellipsoid. The potential energy surfaces of the present TEMs compare favorably with those of the corresponding Gay-Berne and the site-site models. Monte Carlo simulations with 320 particles are performed for a symmetric interaction TEM and an asymmetric interaction TEM. The asymmetric interaction TEM displays a slightly higher transition temperature than the symmetric interaction TEM indicating that asymmetric interactions can be a driving force in a phase transition. Radial and cylindrical distribution functions of two models in the isotropic phase are similar, but those in the nematic phase are quite different.