Structure and energetics of stoichiometric TiO2 anatase surfaces - art. no. 155409

We present an ab initio density-functional investigation of the structure a nd energetics of several stoichiometric 1 X 1 low-index surfaces of anatase , a TiO2 polymorph similar to9% less dense and similar to1.2 kcal/mol less stable than rutile. Although our calculations do not reproduce the relative ordering of the two phases that is observed experimentally, the calculated bulk structural and elastic properties of both polymorphs are in excellent agreement with the experiment, suggesting that surface relaxations are cor rectly described as well. As expected, the surface energies of anatase appe ar to be related to the presence of undercoordinated Ti atoms: the surfaces with fourfold-coordinated Ti atoms have a larger energy than those with fi vefold-coordinated Ti. Furthermore, we find that the average surface energy of a TiO2 anatase macroscopic crystal is smaller than that of rutile. Fina lly, patterns in the relaxation of the surface atoms which are com;non to d ifferent surfaces are analyzed.