Methane dissociation on Ni(111): A seven-dimensional to nine-dimensional quantum dynamics study.

Abstract

As one benchmark system of CH4 dissociation on the Ni(111) surface, it is of great significance to explore the role of each degree of freedom (DOF) of reactant CH4 in its first C-H bond dissociation from quantum dynamics simulations. Here, the influence of the CH stretching DOF of methyl limited in C3v symmetry is quantitatively investigated as well as the important role of azimuth. We calculated the sticking probabilities, S0, of ground state (GS) CH4 dissociation on a rigid Ni(111) surface by performing some seven-dimensional to nine-dimensional (9D) quantum dynamics simulations based on one highly accurate and fifteen-dimensional (15D) ab initio potential energy surface which we recently developed. Our direct quantum dynamics results show that S0 of GS CH4 on four given surface impact sites are weakly enhanced by adding the CH stretching DOF of methyl but strongly weakened by the DOF of azimuth. Furthermore, using a 9D quantum dynamics model, we improve the post-treatment model for treating the influence of surface impact sites through a linear relationship between the effective potential barriers and the distances relative to that on the transition state site. These developed high-dimensional quantum dynamics models and improved post-treatments can be usefully extended for studying some complex polyatomic gas-surface reactions by other theoretical groups.