A modified Poisson-Boltzmann equation for a primitive model electrolyte with unequal ion sizes

Abstract

A modified Poisson-Boltzmann equation is derived for a single primitive model electrolyte with unequal ion sizes. Charge oscillations are found which are similar to those found in the restricted primitive model, but which occur at a higher concentration. Calculations for a 1:1 electrolyte are in reasonable agreement with HNC calculations. There is an inconsistency in the anion-cation radial distribution function which can be serious at high concentrations or high electrolyte valencies.