IMPORTANCE OF ENERGY-TRANSFER AND LATTICE PROPERTIES IN H-ATOM ASSOCIATION WITH THE (111) SURFACE OF DIAMOND

This paper reports the results of a classical trajectory study of the dynamics of H-atom association with a radical site on the (111) surfac e of diamond. The association dynamics are affected by the potential b etween the H-atom and radical site, nonbonded interactions between the H-atom and the surface of the lattice, and the lattice vibrational fr equencies. The sensitivity of the association probability to the latti ce frequencies suggests that in a complete theory for association the dynamics of energy transfer from H-atom relative translation to the la ttice modes must be considered. As a result, a capture theory like tra nsition-state theory is expected to overestimate the association rate constant. The trajectories also show that once the H-atom associates t here is a negligible initial transient in the ensuing dissociation of this H-atom from the lattice. The trajectory results are found to be s ensitive to the treatment of zero-point energy. A quasiclassical traje ctory calculation as performed here, which includes lattice zero-point energy, is expected to give a larger abstraction/addition rate consta nt ratio for a H-atom interacting with a diamond surface than does a m olecular dynamics calculation, which does not include lattice zero-poi nt energy.