Quantum-mechanical calculation of H on Ni(001) using a model potential based on first-principles calculations

First-principles density-functional calculations of hydrogen adsorption on the Ni (001) surface have been performed in order to get a better understanding of adsorption and diffusion of hydrogen on metal surfaces. We find good agreement with experiments for the adsorption energy, binding distance, and barrier height for diffusion at room temperature. A model potential is fitted to the first-principles data points using the simulated annealing technique and the hydrogen band structure is derived by solving the three-dimensional Schrödinger equation. We find vibrational excitation energies slightly too high, with about 10%, compared with experiments and very narrow hydrogen bands. The experimentally observed absence of a pronounced isotope effect for hydrogen diffusion at low temperatures is discussed in terms of tunneling in a static three-dimensional potential.