Density-functional theory for systems of hard rods

Abstract

We present a density-functional theory, based on the smoothed density approximation, to study systems of hard rods with full translational and orientational freedom. For hard spherocylinders, we find both the nematic-isotropic and the nematic–smectic-A transition in a wide range of length-to-width ratios (L+D)/D. We locate the tricritical point for the nematic–smectic-A transition and also make some predictions about the nematic–smectic-A–smectic-B point. Finally, we calculate the nematic elastic constants. The predictions of our theory are compared with the results of computer simulations and other theories. We also make some comments about application of the theory to systems of hard ellipsoids of revolution and hard cylinders.