  We present a density-functional theory study addressing the energetics and
electronic structure properties of isolated oxygen adatoms at the SrTiO3(001)
surface. Together with a surface lattice oxygen atom, the adsorbate is found to
form a peroxide-type molecular species. This gives rise to a non-trivial
topology of the potential energy surface for lateral adatom motion, with the
most stable adsorption site not corresponding to the one expected from a
continuation of the perovskite lattice. With computed modest diffusion barriers
below 1 eV, it is rather the overall too weak binding at both regular
SrTiO3(001) terminations that could be a critical factor for oxide film growth
applications.
