A new representation of the potential energy surface (PES) for diatomic moleculendash;solid surface interactions is presented. It is based upon a delocalized effective medium form (i.e., homogeneous gas analogy) plus empirical twohyphen;body terms and is transferable from face to face of a crystal. We have determined the parameters for H2ndash;Cu and H2ndash;Ni from experimental measurements of Hndash;Cu and Hndash;Ni adsorption energy, frequency, and height and from limited molecular beam scattering data. The PES for H2ndash;Ni(100), Ni(110), Ni(111), and H2ndash;Cu(110), Cu(100) are presented. A dynamical simulation using the classical trajectoryhyphen;generalized Langevin equation lsquo;lsquo;ghostrsquo;rsquo; 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 manyhyphen;body expansion approach lsqb;J. Chem. Phys.84, 485 (1986)rsqb; 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 H2ndash;Cu systems. Quantitative agreement is not obtained especially for the surfaces which exhibit barriers to dissociation. The PES for H2ndash;Ni(111) is different from the previous one and suggests an interesting dissociation mechanism. It was also found that the participation ofdelectrons is essential for the structure sensitivity of the H2dissociative chemisorption on Ni surfaces. On Cu with a 3d104s1configuration, no promotion of 4sto 3delectrons is possible and much less structure sensitivity is shown.
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