Using first-principles density-functional calculations we have studied the interactions of molecular oxygen with a partially reduced rutile ${\mathrm{TiO}}_2$ (110) surface. In agreement with experiments, a number of different ${\mathrm{O}}_2$ adsorption states, both molecular and dissociated, have been found. The kinetic barriers for conversion between these states have also been calculated. Based on these results, we analyze the mechanism of oxygen vacancy diffusion, recently observed by Scanning Tunneling Microscopy (STM), and suggest a pathway which does not imply the high oxygen adatom reactivity assumed in the original model.

• Received 22 August 2003

DOI:https://doi.org/10.1103/PhysRevB.68.241402