The influence of image interactions on the structure of water and electrolytes in front of a metal surface

Abstract

The structure of liquid water in contact with a metallic planar wall is calculated for the central force water model which is a stoichiometric mixture of partially charged hydrogen and oxygen atoms interacting via effective spherical pair potentials. The density profiles near the wall are obtained from the Wertheim–Lovett–Mou–Buff equation where the bulk information enters through the direct correlation functions. In this approach image interactions which are characteristic for a metallic boundary, and which cannot be treated as a simple particle–wall interaction are considered within a mean-field ansatz. We discuss the structural properties of the interface layer for both cases, the charged and the uncharged wall, and compare the results to those for an unpolarizable boundary where the image forces have been switched off. The differential capacitance as function of the wall charge is seen to show a characteristic “hump” which can be related to the transition between two possible icelike water structures in front of the wall.