Molecular dynamics study of the effects of translational energy and incident angle on dissociation probability of hydrogen/deuterium molecules on Pt(111)

The dissociation probabilities of H₂ and D₂ molecules on a Pt(111) surface with thermal motion were analyzed using the molecular dynamics (MD) method. The potential constructed using the embedded atom method was used as the interaction potential between a gas molecule and the surface. The effects of changing the translational energy and incident polar angle of D₂ molecules impinging on a Pt(111) surface were analyzed using MD simulations. The effect of initial orientation, incident azimuthal angle, rotational energy of gas molecules, and the impinging points on the surface were averaged by setting the initial values in a random manner. When the molecules approach normal to the surface, the dissociation probability increases with the initial translational energy. At larger incident angles, the probability becomes smaller. The impinging processes were categorized in terms of reaching the chemisorption layer by analyzing the repulsion forces from the surface. The effective translational energies for impingement, both normal and parallel to the surface, play important but different roles in terms of molecules reaching the chemisorption layer and the dissociation probability. The results were compared to those obtained by molecular beam experiments to check the validity of the simulations. The results indicate that the dependence of the dissociation probability on the translational energy and incident angle is in approximate agreement with that from experiments.