The interfacial structure of a mixture of charged hard spheres and dipolar hard spheres near a charged wall

Abstract

The interfacial structure of an electrolyte near an electrode is examined using dipolar hard spheres as a model solvent. Results are obtained using both the mean spherical approximation and a simple extension. Reasonable agreement with experiment is obtained without the use of adjustable parameters. The results are formally identical to those based upon the use of a continuum dielectric medium as a model for the solvent, together with the concept of an inner layer with a dielectric constant different from the bulk value. However, the microscopic picture is quite different. In this treatment, the interfacial region of the solvent extends several layers into the fluid. This indicates that the concept of an inner layer is of limited utility.