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

The (1 x 2) adsorption of atomic Cl on the stoichiometric and the reduced r utile TiO2 (110) surface was investigated from ab initio by applying the fu ll-potential augmented plane wave method. According to the calculated adsor ption 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 similar to 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 a re increased by 1-2 eV, depending on substrate stoichiometry and adsorption geometry. STM images, calculated according to the model of Tersoff and Ham ann are in good agreement with experiment. (C) 2000 Elsevier Science B.V. A ll rights reserved.