Fast off-lattice Monte Carlo simulations of soft-core spherocylinders: Isotropic-nematic transition and comparisons with virial expansion

Abstract

We proposed a novel anisotropic soft-core potential for spherocylinders that takes into account the degree of overlap between two spherocylinders, thus superior to other soft-core spherocylinder models depending only on the minimum distance between two line segments representing spherocylinders, for example, that used by Vink and Schilling [Phys. Rev. E 71, 051716 (2005)]. Using Monte Carlo simulations in an isothermal-isobaric ensemble with replica exchange at different pressures and multiple histogram re-weighting technique, we studied the isotropic-nematic transition of both models, which recover the standard model of hard spherocylinders for liquid crystals as the repulsion strength ε → ∞, and compared simulation results with virial expansion predictions. We found that isotropic-nematic transition still occurs at high enough densities even for small ε, and that virial expansion predictions become more accurate with increasing aspect ratio of spherocylinders and should be exact in the limit of infinitely large aspect ratio.