Entropy Calculations for Charged Spheres and the Entropy of Molten Salts

Abstract

We derive an expression for the entropy S of a system of charged hard spheres within the Mean Spherical Approximation (MSA). We study the behaviour of the coulombic contribution as a function of both the charging process and the ionic radii ratio. We find that the latter gives an important ordering contribution to S, which is greatly exaggerated in the MSA. We have also calculated S using the data appropriate for the molten alkali halides. The results compare poorly with the experimental entropies and therefore cast doubts on the MSA as a suitable reference system for molten salts.