Small Au clusters oxidation: an ab initio study

We have performed ab initio calculations in the Density Functional Theory framework on unsupported small gold clusters with size ranging from three to seven atoms. In our calculations we have introduced a single O2 molecule on different places around the cluster surface, and in both parallel and perpendicular position with respect to the cluster surface. We have found that the oxygen molecule bonds in-plane with the bidimensional Au cluster when the number of Au atoms is even, and it will be adsorbed off-plane if the number of Au atoms is odd. The latter case, despite not presenting a true chemical bonding, has great stability due to spin pairing and electrostatic interactions, and the structures will be distorted respect to the geometry of their pure Au cluster equivalents.