The use of a non-spherical reference potential in statistical mechanical perturbation theory

Abstract

The computational details of the statistical mechanical perturbation theory for linear, quadrupole fluids using a non-spherical reference potential are considered. It is found that relatively few terms in the series make a significant contribution, so that the extent of the calculations to be done using this perturbation method is not very much more than with other perturbation theories. Further, the perturbation series has been found to be rapidly convergent with, in many cases, perhaps only one term in the series being needed. Simple, approximate correlations for the first and second order terms in the Helmholtz free energy and pressure expansions are given which use only molecular diameter, length and quadrupole moment, and macroscopic properties.