ROLE OF THE SURFACE SITE IN THE KINETICS OF H ATOM ASSOCIATION WITH DIAMOND SURFACES

The reaction path Hamiltonian model and the MAPS/HDIAM analytic potent ial energy function were used in a canonical variational transition st ate theory (CVTST) study of H atom association with diamond surfaces. CVTST rate constants are compared for H atom association with a terrac e site on the diamond {111} surface and two ledge sites on this surfac e. The CVTST association rate constant is largest for the terrace site and is 3.9 and 2.4 times larger than the rate constant for one of the ledge sites at 300 and 2000 K, respectively. Nonbonded interactions b etween the associating H atom and surface H atoms decrease the attract iveness and increase the repulsiveness of the radial and angular poten tials, respectively, along the association reaction path. The CVTST ra te constants are found to be in good agreement with classical trajecto ry rate constants, also calculated for the MAPS/HDIAM potential. This study shows how nonbonded interactions and steric effects may affect r ate constants for diamond surfaces.