A theoretical study of the adsorption dynamics of hydrogen on Ni(111) surface

Abstract

The dissociative chemisorption of a beam of molecular hydrogen on the Ni(111) surface was simulated by classical trajectories calculations, using an LEPS potential for the interaction of H2 with Ni(111) surface built from ab initio results available for the H atom interacting with Ni clusters. In the most favoured reaction path, the adsorption of H2 is activated, with a small barrier (140 meV) in the entrance channel, followed by a small well in the exit channel, separated by a narrow saddle point region from the H-H bond breaking well. The results show that (a) the dissociative adsorption probability Pa increases steadily with collision kinetic energy Ecol, showing a trend in good agreement with nozzle beams experiments; (b) the H2 vibrational energy is less important than the translational one in favouring adsorption with H-H bond breaking; (c) Pa increases when the incident polar angle of the beam increases from Θ = 0° up to Θ = 25-30°, and then it decreases rapidly to zero when Θ increases from 25-30° to 60°; (d) azimuthal corrugation effects on Pa are present at incident angles greater than 15°.