Structural and electronic properties of oxygen vacancies in cubic and antiferrodistortive phases of SrTiO3 -: art. no. 180102

The structural and electronic properties of oxygen vacancy (V-O) defects in cubic and antiferrodistortive (AFD) phases of bulk SrTiO3 are investigated using results from first principles pseudopotential calculations. By systematically increasing the supercell size from 40 to 320 atoms, we show that large supercells are necessary to investigate the structural energetics of this seemingly simple defect properly. With the increase in the supercell size, the formation energy of V-O decreases by similar to1.3 eV due to long-ranged relaxations, and the character of the defect wave function changes from a deep to a shallow level. Calculations indicate that presence of V-O decreases the relative stability of the AFD phase over the cubic phase, consistent with recent experimental results, which find a lowering of the AFD-cubic transition temperature in samples with higher V-O concentrations.