Helium and argon Interactions with gold surfaces: ab initio-assisted determination of the He-Au pairwise potential and its application to accommodation coefficient determination

Abstract

Global potentials for the extremely weak interaction between the He atom and gold surfaces are determined from ab initio calculations and validated with experimental-based determinations of well depth values. Dispersionless density functional periodic calculations are combined with effective pairwise functional parameters for the dispersion. These parameters are obtained from time-dependent density functional theory response theory using localized Hartree-Fock orbitals, as applied on He-Au clusters. This He-Au pairwise potential is used in molecular dynamics simulations of gas-gold surface collisions from which incident and reflected gas atom velocities allow the determination of energy and momentum accommodation coefficients. Boundary quantities such as slip velocity and thermal resistance are not only derived from these coefficients, but also from a new methodology based on a nonparametric kernel, avoiding the atomic description of the gold surface. Similar collision simulations are performed for Ar for comparison. A model of a rough gold surface is also investigated.