A THEORETICAL MOLECULAR-ORBITAL APPROACH TO THE ADSORPTION AND ABSORPTION OF ATOMIC-HYDROGEN ON NI(111)

A semiempirical molecular orbital approach to the H-Ni interaction for a hydrogen atom adsorbed on the (111) surface or immersed in the bulk of Ni is given. The results show that the chemisorptive surface sites are more stable than the subsurface interstitials and that the bulk octahedral sites are more stable than the tetrahedral sites, in agreement with earlier models. The repulsive influence on hydrogen atom adsorption due to other hydrogen atoms residing in the nearer subsurface interstitials is also considered and discussed in terms of electronic arguments.