Theoretical studies of the dissociative adsorption of H₂ on Ni(001) using ab initio parameterized LEPS calculations

Semi-empirical London-Eyring-Polanyi-Sato (LEPS) calculations are reported, comparing the energetics of H₂ dissociation at linear, twofold, and fourfold sites on Ni(001). Parameters for the LEPS method were obtained from the results of first principles calculations of both atomic and molecular hydrogen adsorption on model Ni(001) surfaces. Several pathways are found to require no activation energy for dissociation, of which the most favorable is dissociation across a twofold site with subsequent atomic adsorption at fourfold sites. The experimentally observed β₁ (high coverage) state is found to be consistent with a geometry in which two hydrogen atoms are adsorbed at a single fourfold site.