Quantum-chemical simulation of Al- and Sc-bound hole polarons in BaTiO3 crystal

Quantum-chemical modelling of impurity-bound hole polarons in BaTiO3 crysta l was carried out employing the semi-empirical method of intermediate negle ct of differential overlap (INDO) modified for crystals. Two-site hole has been found to be the most common configuration in the BaTiO3 crystal doped with Al or Sc atoms. The automated geometry optimisation was carried out to obtain the polaron spatial configuration and atomic displacements in the d efective region. The Delta SCF calculated absorption energy for the alumini um-bound polaron was found to be equal to 0.27 eV and the corresponding abs orption energies for scandium-bound polaron were computed to be 1.92 and 0. 62 eV. (C) 2000 Elsevier Science B.V. All rights reserved.