DEMIXING IN HARD ELLIPSOID ROD-PLATE MIXTURES

The phase behavior of fluid mixtures of hard uniaxial ellipsoids with elongations e and 1/e, and equal molecular volume, has been studied us ing constant-pressure Gibbs ensemble Monte Carlo simulations for e = 1 5 and e = 20. Four distinct phases are observed: isotropic (I), uniaxi al nematic (N+ and N-) and biaxial nematic (B). The region of stabilit y of the biaxial phase is found to be limited severely by demixing int o two coexisting uniaxial phases. This is in agreement with recent the oretical predictions. The theory, however, does not account for the su rprising asymmetry of the phase diagram that we find in our simulation s. (C) 1997 American Institute of Physics.