Dissociative and non-dissociative adsorption dynamics of N2 on Fe(110)

Abstract

We study the adsorption dynamics of N₂ on the Fe(110) surface. Classical molecular dynamics calculations are performed on top of a six-dimensional potential energy surface calculated within density functional theory. Our results show that N₂ dissociation on this surface is a highly activated process that takes place along a very narrow reaction path with an energy barrier of around 1.1 eV, which explains the measured low reactivity of this system. By incorporating energy exchange with the lattice in the dynamics, we also study the non-dissociative molecular adsorption process. From the analysis of the potential energy surface, we observe the presence of two distinct N₂ adsorption wells. Our dynamics calculations show that the relative population of these adsorption sites varies with the incident energy of the molecule and the surface temperature. We find an activation energy of around 150 meV that prevents molecular adsorption under thermal and hypothermal N₂ gas exposure of the surface. This finding is also consistent with the available experimental information.