Double-layer interaction in the primitive model and the corresponding Poisson-Boltzmann description

Abstract

Using the anisotropic hypernetted chain approximation, we obtain accurate evaluations of the double-layer repulsion or attraction within the primitive model of electrolyte solutions. Most of the results are different from the predictions of the nonlinear Poisson-Boltzmann (PB) theory. However, the effects of finite ion size and electrostatic ion-ion correlations counteract each other, and, for large surface separations, one can bring the PB theory with a suitably chosen effective surface charge to fit the accurate calculations. The difference between the real and the effective surface charges can partly be considered as a nonspecific, electrostatic "adsorption" of ions to the surface. Show more