QUANTUM-MECHANICAL CALCULATION OF H ON NI(001) USING A MODEL POTENTIAL BASED ON FIRST-PRINCIPLES CALCULATIONS

First-principles density-functional calculations of hydrogen adsorptio n on the Ni (001) surface have been performed in order to get a better understanding of adsorption and diffusion of hydrogen on metal surfac es. We find good agreement with experiments for the adsorption energy, binding distance, and barrier height for diffusion at room temperatur e, A model potential is fitted to the first-principles data points usi ng the simulated annealing technique and the hydrogen band structure i s derived by solving the three-dimensional Schrodinger equation, We fi nd vibrational excitation energies slightly too high, with about 10%, compared with experiments and very narrow hydrogen bands. The experime ntally observed absence of a pronounced isotope effect for hydrogen di ffusion al low temperatures is discussed in terms of tunneling in a st atic three-dimensional potential.