Chemisorption of atomic hydrogen on large-nickel-cluster surfaces

First-principles Hartree-Fock calculations are reported for binding of a hydrogen atom at high-symmetry sites of low-index faces of Ni surfaces (using an Ni20 cluster as a model). Chemisorption energies increase with ligancy of the binding site, with bond energies of 1.6, 2.8, 3.2, and 3.0 eV for onefold, twofold, threefold, and fourfold sites, respectively. A reverse trend is found for e with values of 275, 170, 150, and 73 meV for ligancies of 1, 2, 3, and 4, respectively.