Semirigid vibrating rotor target model for CH4 dissociation on a Ni(111) surface

We present a theoretical treatment of the semirigid vibrating rotor target model to study dissociative chemisorption of CH4 at the atop site on Ni(111) surface. In this treatment, the fixed-site approximation is used to study chemisorption of methane on Ni treated as a rigid and locally flat surface. This results in a four-dimensional (4D) theoretical model to treat methane dissociation on Ni. Using parameters from ab initio calculations, an empirical potential energy surface is constructed for the CH4/Ni(111) system over the atop site. A 4D quantum dynamics calculation using the time-dependent wave-packet method is carried out on this potential energy surface. Our calculation shows that the dissociation probability of methane is an increasing function of kinetic energy, and the C-H stretching vibration significantly enhances the dissociation. The dissociation probability has a strong dependence on the initial orientation of the molecule. Reasonably good agreement is found between the current theoretical calculation and experimental results. (C) 2002 American Institute of Physics.