Xiao Yan Chang, Donald L. Thompson and Lionel M. Raff
J. Chem. Phys. 100, 1765 (1994)
Abstract
The semi-empirical hydrocarbon potential-energy surface developed by Brenner is employed to investigate the minimum-energy pathway for hydrogen-atom diffusion on a diamond (111) surface. Three possible diffusion paths are investigated. These are (a) diffusion to an equivalent site on an adjacent hexagon, (b) diffusion to an adjacent site in the meta position relative to the initial site, and (c) diffusion to an adjacent site in the para position relative to the initial site. These paths are found to be associated with potential barriers of 4.4, 3.9, and 3.29 eV, respectively. Thermal rate for path (b) computed from classical jump frequencies obtained using variational transition-state methods yield values of 2.3 x 10-21 s-1 and 4.2 x 10-30 s-1 at 300 and 600 K, respectively. The phonon-assisted tunneling rate is computed using a WKB method combined with a classical variational transition state theory. The results show that tunneling is insignificant at temperatures typically used in diamond-film synthesis.