Chemisorption of hydrogen on the nickel (111) surface

Abstract

The chemisorption of atomic H on the [111] surface of Ni is treated by use of a many-electron embedding theory to describe the electronic bonding. The lattice is modeled as a 26-atom, three layer cluster which is extracted from a larger cluster by an orbital localization transformation. Ab initio valence orbital CI calculations carried out on a local surface region permit an accurate description of bonding at the surface. H atoms are found to bind strongly to the Ni(111) surface at threefold and bridge sites. Calculated H binding energies are in the range 2.50–2.66 eV, for optimized Ni–H bond lengths ranging from 1.81 to 1.87 Å. Vibrational frequencies are in the range 1043–1183 cm−1. The binding energy of H at an atop atom site is 1.94 eV. The work function increases by ∼0.2 eV on H adsorption.