First principles studies of chemisorbed O on Ni{1 1 1}

The p( 3× 3) structure formed at saturation by dissociative adsorption of O ₂ on Ni{1 1 1} is investigated by means of first-principles density functional theory. Occupation of fcc hollow sites is favoured over hcp, with atop and bridge sites determined to be maxima and saddle points, respectively, in the potential energy surface. The calculated heat of adsorption (4.21 eV per O ₂ molecule) and work function increase upon adsorption (0.72 eV) are in good agreement with experiment, and the flow of electrons from the surface to O 2p _x and 2p _y orbitals is found to outweigh the counter-flow from O 2p _z to the surface.