FORMATION AND DYNAMICS OF HOT-PRECURSOR HYDROGEN-ATOMS ON METAL-SURFACES - TRAJECTORY SIMULATIONS AND STOCHASTIC-MODELS

The results of a theoretical study of H atoms colliding with a Cu(lll) surface are presented. The metal is treated as a five-layer slab of 1 50 atoms, and all dynamics are classical. The formation of trapped ''h ot-precursor'' atoms on the surface is examined, as well as the nature of their motion on the surface and their energy and momentum dissipat ion. Connections are made with recent Eley-Rideal experiments, for whi ch hot-atom precursors may play an important role. To facilitate futur e simulations of Eley-Rideal and hot-atom reactions on metals, simple stochastic models are developed to describe hot-atom energy dissipatio n. A Fokker-Planck equation is used to model the hot-atom energy distr ibution. Quasi-Langevin terms, which simulate fluctuation and dissipat ion consistent with this Fokker-Planck description, are developed for the hat-atom equations of motion. These quasi-langevin terms are diffe rent from the hydrodynamic forms used for Brownian-type motion. (C) 19 98 American Institute of Physics.