Eley-Rideal and hot-atom dynamics of HD formation by H(D) incident from the gas phase on D(H)-covered Cu(111)

We have performed a quasi-classical molecular dynamics study of the reactio n dynamics of HD formation by H or D atoms incident from the gas phase on a D or H-covered Cu(lll) 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 sche me. Our preliminary study supports the Rettner-Auerbach scenario that a sig nificant fraction of the reactions occurs via hot-atom pathways as opposed to Eley-Rideal pathways, in which the incident atom reacts directly with th e adsorbed atom. The calculated reaction probabilities and re-vibrational d istributions are in good agreement with the measured distributions. As obse rved experimentally on other metal surfaces, we also find that the incident atom induces secondary reactions among the adsorbates, producing either H, or D, molecules. The magnitude and the isotope dependence of the calculate d secondary reaction probabilities are in good agreement with measured valu es.