Calculation of the cadmium–water interface

Abstract

This paper presents the results of a very nearly ab initio calculation of the molecular and electronic distributions at the interface of hcp cadmium and liquid water. The calculated results were obtained by combining a molecular dynamics simulation for the H2O molecular distributions with a self-consistent 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 each time step of the molecular dynamics simulation, with the electron–H2O and 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 the interface. Results are given for the equilibrium structure of interface, and its response to applied potentials. An analysis of the electrostatics of the interface yields a prediction for the compact capacitance of the cadmium–electrolyte interface, which is compared to experiment.