Al-bound hole polarons in TiO2

Changes in the structural and electronic properties of TiO2 (anatase and rutile) due to the Al-doping are studied using a quantum-chemical approach based on the Hartree-Fock theory. The formation of hole polarons trapped at oxygen sites near the Al impurity has been discovered and their spatial configuration are discussed. The occurrence of well-localized one-center hole polarons in rutile may influence its photocatalytic activity. Optical absorption energy for this hole center is obtained, 0.4 eV, using the Delta SCF approach. (C) 2009 Elsevier B.V. All rights reserved.