Coulombic interaction restricted primitive model

Here is the radius of particle a. The hard wall repulsion is equivalent to the introduction of a distance of closest approach for the counterions in order to define a Stem layer thickness. In a more restricted primitive model the radius a is set identical for all ionic species. The Coulomb term in 3.6.3] represents the interaction of an ion with a charge q at jc, with the surface charge and its image. According to Coulomb s law. 

In this section we consider the application of the concept of ion association to describe the properties of electrolyte solutions within the ion or McMillan-Mayer level approach. In this approach the effects of solvent molecules are taken into account by introducing the dielectric constant into Coulomb interaction law and by appropriately choosing the short-range part of ion-ion interactions. To simplify, we consider here the restrictive primitive model (RPM)... 

Models of molten salts have evolved with time and so have the inter-ionic potentials relevant to them. The restricted primitive model (RPM) considers the ions to be charged hard spheres of uniform size (radius rj) interacting through their coulomb potentials. The potential function is then ... 

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