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

Quantum-chemical modelling of impurity-bound hole polarons in BaTiO3 crystal was carried out employing the semi-empirical method of intermediate neglect 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 defective region. The ΔSCF calculated absorption energy for the aluminium-bound polaron was found to be equal to 0.27 eV and the corresponding absorption energies for scandium-bound polaron were computed to be 1.92 and 0.62 eV.