NEW THEORETICAL DESCRIPTION OF ELECTRIFIED INTERFACES

Starting from a Landau-Ginzburg-like Hamiltonian we have analysed an e xtension of the Gouy-Chapman theory. It contains three phenomenologica l parameters describing the overall effect of interionic correlations. We show that the expression for the differential capacitance takes a simple and very suggestive form. We use a numerical method to calculat e ionic profiles and diffuse layer capacitance. Depending on the param eters, a variety of behaviours for the charge dependence of capacitanc e can be generated. We discuss the consequences of our model for the i nterpretation of experimental data based on the Parsons-Zobel plot.