A comparison between molecular-dynamics and theoretical results for the structure of fluids of hard ellipsoids

Abstract

For fluids of hard ellipsoids of revolution the pair distribution function can be expressed as an expansion in products of spherical harmonics. In this paper molecular-dynamics results are given for eight coefficients in this expansion and detailed comparisons are made with the hypernetted-chain (HNC) and Percus-Yevick (PY) approximations. Ellipsoids with length-to-breadth ratios of ⅓, 2, 3 and 5 are considered, and in some cases results are reported for different densities. It is shown that both the HNC and PY theories are in reasonable agreement with molecular-dynamics results for prolate particles. The accuracy of the theories improves with decreasing density as expected, but does not depend strongly upon the length-to-breadth ratio for the prolate systems considered. For oblate ellipsoids the HNC theory remains in very good agreement with the molecular-dynamics results but the PY approximation is less accurate, tending to be rather poor for some coefficients.