Energy Dissipation Effects on the Adsorption Dynamics of N 2 on W(100)

Abstract

Adsorption dynamics of N 2 on the W(100) surface is studied by means of quasi-classical trajectories making use of a six-dimensional potential energy surface obtained from density functional theory calculations. In our simulations, van der Waals (vdW) interactions are accounted for by using the vdW-DF2 functional. In view of the comparison with experiments, we show that this leads to a good description of the adsorption dynamics, providing a significant improvement with respect to semi-local exchange-correlation functionals used in the past. Particular emphasis is placed on the description of nonactivated pathways, leading to either dissociation or molecular adsorption. Dynamics calculations are performed within the generalized Langevin oscillator (GLO) model in order to simulate the energy exchange between molecule and surface atoms. Electron-hole (e-h) pair excitations are also implemented in the dynamics via the local density friction approximation (LDFA). Overall adsorption probability, including dissociative and nondissociative mechanisms, is enhanced when molecules can lose energy through surface phonons and electronic excitations. However, the energy exchange with phonons has a larger influence in the adsorption probability than e-h pair excitations. Nondissociative molecular adsorption only takes place when such energy dissipation channels are included in the simulations, underlying the importance of GLO and LDFA models in such theoretical studies.