COMPUTER-SIMULATION STUDIES OF THE DEPENDENCE ON DENSITY OF THE ORIENTATIONAL ORDER IN NEMATIC LIQUID-CRYSTALS

Simulations of the temperature dependence of the nematic orientational order parameter, PBAR2, at different densities have been made using the Gay-Berne potential. The results are used to calculate GAMMA = -(partial derivative ln T/partial derivative ln V)PBAR2, which is a measure of the relative sensitivity of PBAR2 to temperature and density. Previous experimental measurements of GAMMA have obtained values in the range 2-6 for real nematogens, whilst the present simulations yield GAMMA = 8 +/- 1. Changing the Gay-Berne potential by increasing the steepness of the repulsive term increases the calculated value of GAMMA, whilst changing the relative well depths for side-by-side compared to end-to-end arrangements of Gay-Berne Berne particles leaves GAMMA virtually unchanged. These exploratory calculations suggest that GAMMA is a useful parameter for testing the parametrizations of model potentials.