Charging of the liquid metal surface and the capacitance of the metalndash;electrolyte interface

摘要

Density profiles for the conduction electrons of a simple liquid metal are calculated for a series of surface charge densities, using the selfhyphen;consistent Kohnndash;Sham approach with an oscillatory density profile for the distribution of positive ions. The effect of charging on the electronic density profile is discussed. Considering an interface between the metal and an electrolyte phase such that the two phases have no common charged components (polarizable electrode), we derive an expression for the capacitance in terms of the centroids of the induced charge densities in the two phases, which are themselves functions of surface charge density. The calculated electron density profiles are used to calculate these centroids and to estimate the position of adsorbed water of the electrolyte phase relative to the position of the metal positivehyphen;ion profile. From these one obtains the capacitance of the interface; the contribution of nonideality of the metal is shown to be important.