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