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) surface of diamond. The association dynamics are affected by the potential between the H-atom and radical site, nonbonded interactions between the H-atom and the surface of the lattice, and the lattice vibrational frequencies. The sensitivity of the association probability to the lattice frequencies suggests that in a complete theory for association the dynamics of energy transfer from H-atom relative translation to the lattice modes must be considered. As a result, a capture theory like transition-state theory is expected to overestimate the association rate constant. The trajectories also show that once the H-atom associates there is a negligible initial transient in the ensuing dissociation of this H-atom from the lattice. The trajectory results are found to be sensitive to the treatment of zero-point energy. A quasiclassical trajectory calculation as performed here, which includes lattice zero-point energy, is expected to give a larger abstraction/addition rate constant ratio for a H-atom interacting with a diamond surface than does a molecular dynamics calculation, which does not include lattice zero-point energy.