A new ab initio potential energy surface for hydrogen atom on ruthenium(0001) and its use for variational transition state theory and semiclassical tunneling calculations of the surface diffusion of hydrogen and deuterium

Abstract

We have applied variational transition state theory with a semiclassical tunneling method to calculate the rates of hydrogen and deuterium diffusing on a Ru(0001) surface. The hydrogen-metal interaction is modeled by a pairwise potential which has been fitted to electronic structure calculations based on a local density approximation and a pseudopotential. We present diffusion coefficients and kinetic isotope effects fort the temperature range from 80 to 800 K using the fitted potential and also for two modified potentials ― one in which the potential along the minimum-energy path is scaled by a constant and one in which the pairwise potential parameters are modified to change the barrier height. The results for all three potentials are compared to experimental rate coefficients determined recently by laser-induced thermal desorption