A field theoretic approach to the electric interfacial layer: mixture of trivalent rod-like and monovalent point-like ions between charged walls

In this paper, we study the interaction between charged macroions (surfaces) immersed in a solution of oppositely charged, rod-like counterions and point-like co-ions. The system is modeled by a field theoretic approach, which was extended to treat mixtures of rod- and point-like ions. The theory is applicable from the weak to the intermediate through to the strong coupling regimes. In the weak coupling limit, the force between the charged surfaces are only repulsive. In the intermediate coupling regime, the rod-like ions can induce attractive force between the charged surfaces. In the strong coupling limit, the inter-ionic charge correlations dominate the attractive forces at short separations between the charged surfaces.