Studies in statistical mechanics of Coulombic systems. I. Equation of state for the restricted primitive model

Abstract

Thermodynamic properties for a system consisting of charged hard spheres are investigated in the liquid state. A Padé type approximant which satisfies certain known limiting features of this model is fitted to Monte Carlo calculated internal energies previously reported. Other thermodynamic properties are derived from this energy equation of state and compared with experimental results for some molten alkali halides. It is found that the primitive model system shows a thermodynamic behavior that is remarkably similar to a typical alkali halide in the liquid phase. This similarity is explained in terms of the similar basic properties of the pair potential, namely the short range repulsion and the long range Coulomb contribution which are sufficient for a typical molten salt structure to be formed.