Salty solutions near a charged modulated interface

Charged monolayers at a liquid-vapor interface may be found in a crystalline state, resulting in a surface density of charge that displays periodic modulations. In this paper we discuss how these modulations affect different thermodynamical and mechanical properties (compared with the equivalent uniform charge density) of a system consisting of the charged monolayer and a bulk solution including a finite concentration of counter-ions and co-ions. It is shown that very accurate results for low and moderate salt concentrations are possible within an expansion in the Fourier modes of the modulations, the Weak Amplitude Perturbation (WAP), if the finite size of the ions are included as a Stern layer. We conclude by discussing the implications and the relevance of these results for both theoretical studies and experiments.