Computational study of Nb-doped SrTiO3

A study of Nb doping in cubic and tetragonal strontium titanate (SrTiO3) has been carried out using a quantum-chemical method developed for crystals and a periodic Large Unit Cell (LUC) model. One of the Ti atoms, was substituted by Nb atom in LUC consisting of 135 atoms. The optimised geometry in the Nb-surfounding defective region showed considerable differences in the atomic relaxation for two crystallographic phases. Since Nb doping increases the number of valence electrons by one, it leads to the occurrence of a local energy level within the band-gap of the crystal. (C) 2002 Elsevier Science B.V. All rights reserved.