New self-consistent approximations for ionic and polar fluids

Abstract

A general approximation scheme for the pair correlation function of fluids at equilibrium is discussed, and two new specific approximations that come out of it—one for polar fluids and one for ionic fluids—are introduced. The approximation scheme, developed for hard-core particles, is based upon the replacement of the actual structure of the Ornstein–Zernike direct correlation function c (12) outside the core by a form that can be wholly characterized in terms of its poles in Fourier space. The locations and residues of the poles are constrained by thermodynamic self-consistency; the approximate scheme is designated as the self-consistent Ornstein–Zernike approximation (SCOZA) scheme.