Gibbs ensemble simulation of nematic-isotropic coexistence in a liquid crystal mixture

The results are presented of Gibbs ensemble Monte Carlo (GEMC) simulations examining the nematic-isotropic (N-I) coexistence envelope of a liquid crystal mixture. The system studied is a 50:50 mixture of 1000 generalized Gay-Berne particles with axial ratios 2.0:1 and 2.5:1. For this system, stable N-I coexistence is observed over run lengths in excess of 5 x 105 GEMC sweeps. There is unambiguous evidence of fractionation, the mole fractions of long particles in the coexisting phases typically differing by 11%. The measured coexistence envelope does not conform to the lens shape predicted by Onsager theory; qualitative finite size arguments are given in explanation of this distortion.