Computer simulation of a biaxial liquid crystal

Abstract

We report the first results of Monte Carlo simulations using hard ellipsoids with three distinct semi-axes a, b, c chosen such that abc = 1, c/a = 10 and b/a varies between 1 and 10. A survey of the phase diagram provides evidence for the existence of isotropic, nematic, discotic, and biaxial liquid crystal phases; this is believed to be the first simulation of a biaxial phase of a bulk liquid with full rotational and translational freedom. We find that the phase diagram is approximately symmetric under the transformation {a, b, c} → {a⁻¹,b⁻¹,c⁻¹}, and that the biaxial phase is most stable at about the expected (self-conjugate) value b= √ac. For this value, the isotropic phase transforms directly into the biaxial phase on compression, at a density at least 50 per cent higher than that at which-the nematic-isotropic transition occurs in the corresponding uniaxial systems. These results are in semi-quantitative agreement with recent theories, but there are also some significant differences.