The application of density functional theory and the generalized mean spherical approximation to double layers containing strongly coupled ions

Density functional theory (DFT) is the most successful simple theory for ions near an electrode (the double layer), However, most previous applications of DFT have been for ions that are relatively weakly coupled; Interesting effects have been found in simulations for ions that are strongly coupled. Specifically, drying of the electrode with a resultant large increase in the magnitude of the adsorption is observed. Further, the capacitance decreases with increasing coupling. The DFT formalism requires the direct correlation function of the bulk electrolyte as input. If the bulk electrolyte is treated by means of the mean spherical approximation (MSA), DFT fails to account for these phenomena. However, if the bulk electrolyte is treated by means of a generalized MSA, partial. success results. The electrolyte dries the electrode but the lowering of the capacitance is predicted only weakly. Further refinements are necessary for full success.