Oxygen adsorption on Cu(100): First-principles pseudopotential calculations

We have studied the adsorption characteristics of atomic and molecular oxygen, incident on the Cu(100) surface. Our pseudopotential first-principles calculations yield trajectories for the O₂ molecule without dissociation barriers at the entrance channel. We discuss the energetics of the O₂ adsorption and dissociation in terms of the elbow plots which are two-dimensional cuts of the full six-dimensional potential-energy surface. The top site is found to be the most reactive one while at the fcc site molecular adsorption takes place. The adsorption energies at horizontal configurations of the O₂ molecule are found to be larger than those at the vertical configurations. The local densities of states reveal differences between the sites with direct dissociative adsorption and the ones with molecular precursor states. We also discuss the interactions between O and Cu atoms adsorbed at the hollow sites on Cu(100), and the corresponding diffusion barriers.