Fizika Nizkikh Temperatur: Volume 46, Number 12 (December 2020), p. 1394-1406 ( to contents , go back )
Ab initio calculations of structural, electronic and vibrational properties of BaTiO3 and SrTiO3 perovskite crystals with oxygen vacancies
L.L. Rusevich, E. A. Kotomin, G. Zvejnieks, and A. I. Popov
Institute of Solid State Physics, University of Latvia, Riga LV-1063, Latvia
Received July 7, 2020, published online October 21, 2020
The first-principles (ab initio) computations of the structural, electronic, and phonon properties have been performed for cubic and low-temperature tetragonal phases of BaTiO3 and SrTiO3 perovskite crystals, both stoichiometric and non-stoichiometric (with neutral oxygen vacancies). Calculations were performed with the CRYSTAL17 computer code within the linear combination of atomic orbitals approximation, using the B1WC advanced hybrid exchange-correlation functional of the density-functional-theory (DFT) and the periodic supercell approach. Various possible spin states of the defective systems were considered by means of unrestricted (open shell) DFT calculations. It was demonstrated that oxygen reduction leads to the appearance of new local vibrational modes associated with oxygen vacancies and new first-order peaks in the Raman spectra, which could be used for defect identification. The calculated Raman spectra for different vacancy positions and spins of the system, as well as other properties of defective crystals, are compared with the relevant experimental data.
Key words: BaTiO3, SrTiO3, oxygen vacancy, DFT hybrid calculations, infrared spectra, Raman spectra.