A variational approach to static correlations in dilute macro-ion suspensions

Abstract

The Gibbs-Bogoliubov inequality is used to determine an effective diameter and charge of a suspension consisting of highly charged colloid particles or micelles, point counter-ions and neutral particles. The reference system is analysed in terms of the mean spherical approximation (MSA), and the full three-component system is reduced to an effective one-component problem in which the macro-ions interact via a screened Coulomb potential. The contact potential and screening length are given in terms of the suspension parameters and radial distribution functions. The results of this procedure are discussed in light of scattering experiments on colloidal and micellar suspensions.