A molecular dynamics study of a steric multipole model of liquid crystal molecular geometry

Abstract

We report results from a series of molecular dynamics simulations designed to study the phase behaviour of model rod-like liquid crystal molecules with different geometries interacting via the Gay-Berne potential. Following the classification of molecular geometry in terms of a multipole expansion in steric asymmetry, two models have been studied in detail: a zigzag model defined as a steric quadrupole and a triangle model defined as a longitudinal steric dipole, and comparison has been made with a cylindrical model. Results from the NVE ensemble indicate that the model steric quadrupole delays the temperature of onset of the nematic phase. Extensive simulations in the NPT ensemble demonstrate a similar trend in the temperature of onset of the smectic B phase, with a lower temperature of onset observed with the steric quadrupole than the steric dipole. Local antiparallel steric ordering within a layer was observed with the model steric dipole in the crystal B phase but not with the model steric quadrupole...