Structural consistency and the fourth virial coefficient for inverse power potentials

Abstract

Exact fourth virial coeficients have been computed for inverse power potentials over the full range of powers which allow thermodynamic stability. Values are given for the exact virial coefficient, together with those from the Percus-Yevick, hypernetted chain and thermodynamically self-consistent approximations. Comparisons show that the thermodynamically self-consistent approximation gives a good account of the variation of the fourth virial coefficient over the full range of inverse powers. A new consistency condition is defined using the pair and triplet direct correlation function, and is shown to be well satisfied by the thermodynamically self-consistent approximation.