| Abstrakt: |
A new representation of the potential energy surface (PES) for diatomic molecule–solid surface interactions is presented. It is based upon a delocalized effective medium form (i.e., homogeneous gas analogy) plus empirical two-body terms and is transferable from face to face of a crystal. We have determined the parameters for H2–Cu and H2–Ni from experimental measurements of H–Cu and H–Ni adsorption energy, frequency, and height and from limited molecular beam scattering data. The PES for H2–Ni(100), Ni(110), Ni(111), and H2–Cu(110), Cu(100) are presented. A dynamical simulation using the classical trajectory-generalized Langevin equation ‘‘ghost’’ atom formalism is implemented in order to calculate the dissociative sticking probability as a function of incident kinetic energy and surface temperature. The calculated probabilities are in general qualitative agreement with those measured experimentally, and are superior to those based upon the previous many-body expansion approach [J. Chem. Phys. 84, 485 (1986)] in the following features: (1) the angular distribution of reflected molecules is more specular, (2) Ni(100) has a barrier for dissociation so that the dissociation probability depends on the translational energy, and (3) the many body expansion approach requires very high order terms for H2–Cu systems. Quantitative agreement is not obtained especially for the surfaces which exhibit barriers to dissociation. The PES for H2–Ni(111) is different from the previous one and suggests an interesting dissociation mechanism. It was also found that the participation of d electrons is essential for the structure sensitivity of the H2 dissociative chemisorption on Ni surfaces. On Cu with a 3d10 4s1 configuration, no promotion of 4s to 3d electrons is possible and much less structure sensitivity is shown. [ABSTRACT FROM AUTHOR] |
