THE EFFECT OF SHORT-RANGE ORIENTATIONAL ORDER ON THE NEMATIC-ISOTROPIC PHASE-TRANSITION

A statistical mechanical perturbation theory, that is derived from our earlier work, is applied to investigate the influence of short-range orientational correlation on the thermodynamic properties of nematic liquid crystals. Two-particle orientational distribution function is used in order to account for the short-range orientational order. Numerical calculations are reported for a model system interacting via a pair potential having both repulsive and attractive parts. The repulsive interaction is represented by that between hard ellipsoids of revolution and is short-range rapidly varying potential. Dispersion forces give rise to the attractive interaction. The effect of pressure on the stability, ordering and phase transition properties is analysed and found to be in accordance with experimental observations. It is found that the short-range orientational order has strong influence on the phase transition properties and the numerical results are in better agreement with experiments as compared to mean-field results.