Interaction between charged surfaces mediated by rodlike counterions: the influence of discrete charge distribution in the solution and on the surfaces.

The interaction between two charged surfaces, with discrete or uniform charge distributions, embedded in a solution of rodlike counterions has been studied. Monte Carlo simulations and density functional theory have been applied to study the concentration profiles of counterions and the force between the charged surfaces. We show that for low surface charge densities the repulsive force between like-charged surfaces is observed regardless of the rod length. Where high surface charge densities are present, attractive forces at surface separations related to the rod length are observed.