Generalized mean spherical approximations for polar and ionic fluids

Abstract

Generalized mean spherical approximations are solved for polar and ionic fluids. They are generalizations of previous mean spherical results in the sense that more general forms for the direct correlation function c(12) are considered than heretofore. In the case of a polar fluid, c(12) outside a hard-sphere core is taken to be a sum of an ideal dipole term, a Yukawa term, and two short-ranged terms, one of which is a shielded dipolar interaction, the other of which is a shielded ``classical Heisenberg'' interaction. In the ionic case, c(12) outside the core is taken to be the sum of Coulomb and Yukawa terms. In both cases, the coefficients of all terms can be independently adjusted. Two applications of our generalized mean spherical results are discussed. The first generates improved approximations with built-in thermodynamic consistency. The second is a more straightforward use of the generalization to provide mean spherical approximations for a wider class of potentials.