Surface embedded atom model of the electrolyte-metal interface

Abstract

We develop a semiempirical interatomic potential model based on the surface embedded atom method (SEAM) for simulating the metal-electrolyte interface in the presence of excess surface charge on the metal electrode surface in an electrochemical cell. We take the excess charge into account by modifying the electron density in the embedding function of the SEAM potential. We calculate total and surface energies and the surface stress as functions of the cell voltage [relative to the potential of zero charge (PZC)] for gold electrodes and compare with reported measurements. The values of the two parameters that occur in our model are fit to the measured work function and capacitance of the Au(111) surface. The parameter corresponding to the height of the surface layer is in close agreement with that obtained from density-functional theory calculations. A similar fit is also carried out for silver electrodes. The calculated values of the PZC for low index faces of gold and silver follow the trend observed experimentally. Our results suggest that the SEAM potentials can reasonably describe the physics of the metal-electrolyte interface.