"Hot-atom" O2 dissociation and oxide nucleation on Al(111).

We propose an atomistic model for the nucleation of aluminum oxide on the Al(111) surface derived from first principles molecular dynamics simulations. The process begins with the dissociative adsorption of O2 molecules on the metal surface, which occurs via a "hot-atom" mechanism driven by the partial filling of the sigma* antibonding molecular orbital of O2. During the subsequent hyperthermal motion, O atoms can be spontaneously incorporated underneath the topmost Al surface layer, initiating the nucleation of the oxide far below the saturation coverage of one (1 x 1) O adlayer.