title: Path integral evaluation of H diffusion on Ni(100) surface based on the quantum instanton approximation.
abstract: The diffusion coefficients for hydrogen on Ni(100) surface are calculated by using the quantum instanton approximation, together with path integral Monte Carlo and adaptive umbrella sampling techniques. The model includes 163 atoms in which the motions of the hydrogen and 25 Ni atoms are treated quantum mechanically and the left Ni atoms are considered classically. At high temperature, the predicted diffusion coefficients are in good agreement with experiments. As temperature decreases to 80 K the hydrogen tunneling begins to dominate the diffusive process and the transition temperature is found to be 70 K under which the diffusion coefficient is nearly independent of temperature. The calculations also indicate that the quantum motions of surface atoms hinder the diffusive process compared to the rigid surface and purely classical motions of surface atoms. The underlying mechanisms are extensively investigated.
authors.affiliation: Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026, People's Republic of China.
authors.forename: Wenji
authors.initials: W
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhao