ELASTIC-CONSTANTS OF NEMATICS COMPARISON BETWEEN MOLECULAR THEORY ANDCOMPUTER-SIMULATIONS

We compare the ratios of the Frank elasticity coefficients calculated within a recently developed molecular theory, based on the approximati on of perfect local orientational order, with the results of computer simulations presented by Frenkel. Allen, Tjipto-Margo and Evans for fl uids of hard prolate and oblate ellipsoids. Good agreement is found fo r high densities, which correspond to those of thermotropic nematics, and for realistic values of the axial ratio. By constrast, at lower de nsities the approximation of perfect local order appears to be inadequ ate and the results of computer simulations follow the predictions of mean-field-like theories.