Multipolar electrolyte solution models. II. Monte Carlo convergence and size dependence

Abstract

Monte Carlo simulations of mixtures of charged and multipolar hard spheres with equivalent diameters are presented. A solution with dipolar solvent at a state point considered earlier, with greatly different results, by Chan et al. [Mol. Phys. 66, 299 (1989)] and by Caillol et al. [Mol. Phys. 69, 199 (1990)] is re-examined. Structural, thermodynamic, and dielectric properties are determined and particle number dependence in these averages is examined. The rate of convergence is shown to be satisfactory for correlation functions, other than that of repulsive ion pairs, and for thermodynamic properties. These are in good agreement with hypernetted chain theory. The reliability of the Metropolis Monte Carlo technique for the evaluation of thermodynamic properties in conveniently small systems of this solution model is established. We also consider a solution in which the solvent has both dipolar and linear quadrupolar symmetry. Two smaller systems give structural and thermodynamic properties in good agreement with hypernetted chain theory. In a larger system ionic clustering occurs to produce very different solution structure.