Calculation of the cadmium-water interface

This paper presents the results of a very nearly ab initio calculation of t he molecular and electronic distributions at the interface of hcp cadmium a nd liquid water. The calculated results were obtained by combining a molecu lar dynamics simulation for the H2O molecular distributions with a self-con sistent density functional calculation for the valence electron density of the cadmium surface. The method employs a three-dimensionally periodic unit cell, uses standard molecular dynamics potentials for H2O-H2O interactions , and calculates a self-consistent electronic structure for the metal at ea ch time step of the molecular dynamics simulation, with the electron-H2O an d electron-Cd interactions represented by pseudopotentials. The electronic and H2O distributions of the Cd-water interface are obtained both for zero applied potential, and for a range of electric potentials applied across th e interface. Results are given for the equilibrium structure of interface, and its response to applied potentials. An analysis of the electrostatics o f the interface yields a prediction for the compact capacitance of the cadm ium-electrolyte interface, which is compared to experiment. (C) 2000 Americ an Institute of Physics. [S0021-9606(00)70806-3].