Electrostatic interaction of oppositely charged double layers

Abstract

We determined with anisotropic hypernetted chain theory the effective pressure and counterion excess of two oppositely charged surfaces immersed in an electrolyte solution. These thermodynamic properties are enhanced in surfaces with evenly smeared surface charges with respect to those containing confined mobile charges. For low surface charges and moderate reservoir salt concentration ions are expelled from the slit between the planes. Depletion arises from ionic charge positional correlations. Its effect was determined through the number of excess of counterions which displays a negative value in the range of low surface charge density. However, a Poisson-Boltzmann calculation lead to positive definite counterion's excess due to its lack of ionic correlations.