Ab initio study of atomic Cl adsorption on stoichiometric and reduced rutile TiO2 (110) surfaces

The (1×2) adsorption of atomic Cl on the stoichiometric and the reduced rutile TiO2 (110) surface was investigated from ab initio by applying the full-potential augmented plane wave method. According to the calculated adsorption energies of the fully relaxed systems, the most favourable adsorption site is at O defects of the reduced surface. On the stoichiometric surface, Cl is preferentially adsorbed on top of the undercoordinated Ti atoms. Cl 3s and 3p states lie ∼2 eV above and on the upper edge of the O 2s and p bands, respectively. The uppermost state of the p band is emptied upon adsorption of Cl on the stoichiometric substrate. The work functions are increased by 1–2 eV, depending on substrate stoichiometry and adsorption geometry. STM images, calculated according to the model of Tersoff and Hamann are in good agreement with experiment.