THE INFLUENCE OF IMAGE INTERACTIONS ON THE STRUCTURE OF WATER AND ELECTROLYTES IN FRONT OF A METAL-SURFACE

The structure of liquid water in contact with a metallic planar wall i s calculated for the central force water model which is a stoichiometr ic 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 th e bulk information enters through the direct correlation functions, In this approach image interactions which are characteristic for a metal lic boundary, and which cannot be treated as a simple particle-wall in teraction are considered within a mean-field ansatz. We discuss the st ructural properties of the interface layer for both cases, the charged and the uncharged wall, and compare the results to those for an unpol arizable boundary where the image forces have been switched off. The d ifferential capacitance as function of the wall charge is seen to show a characteristic ''hump'' which can be related to the transition betw een two possible icelike water structures in front of the wall. (C) 19 97 American Institute of Physics.