(Faraday Discussion no. 110: Chemical Reaction Theory, p. 287 (1998))
Dmitrii Shalashilin, and Bret Jackson
Department of Chemistry, Lederle
Graduate Research Center, University of Massachusetts, Amherst, MA 01003
Mats Persson
Department of Applied Physics, Chalmers University of
Technology, S-412 96 Göteborg, Sweden
We have performed a quasi-classical molecular dynamics study of the reaction dynamics of HD formation by H or D atoms incident from the gas phase on a D or H-covered Cu(111) surface. A key ingredient has been the construction of a model potential energy surface (PES) that has been exclusively based on results from total energy calculations using the density functional scheme. Our preliminary study supports the Rettner-Auerbach scenario that a significant fraction of the reactions occurs via hot-atom pathways as opposed to Eley-Rideal pathways, in which the incident atom reacts directly with the adsorbed atom. The calculated reaction probabilities and ro-vibrational distributions are in good agreement with the measured distributions. As observed experimentally on other metal surfaces, we also find that the incident atom induces secondary reactions among the adsorbates, producing either H2 or D2 molecules. The magnitude and the isotope dependence of the calculated secondary reaction probabilities are in good agreement with measured values.