Fizika Nizkikh Temperatur: Volume 46, Number 12 (December 2020), p. 1418-1425 ( to contents , go back )
First principles hybrid Hartree–Fock–DFT calculations of bulk and (001) surface F centers in oxide perovskites and alkaline-earth fluorides
R. Eglitis1, A. I. Popov1, J. Purans1, and Ran Jia1,2
1Institute of Solid State Physics, University of Latvia, Riga LV-1063, Latvia
2Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University Changchun 130023, PR China
Received August 23, 2020, published online October 21, 2020
We report the results of ab initio calculations and analysis of systematic trends for the F centers in the bulk and on the (001) surface in oxide perovskites, such as BaTiO3, SrTiO3, SrZrO3, and PbZrO3, with a corresponding comparison of the F centers in perovskites with those in alkaline earth metal fluorides (CaF2, BaF2, and SrF2). It was found that in perovskites in both bulk F centers and those on their (001) surfaces, two nearest to the vacancy Ti or Zr atoms repel each other, while the next nearest O atoms relax towards the oxygen vacancy. It was also found that the obtained relaxations of atoms in the nearest neighborhood around the F center in ABO3 perovskites are generally larger than in alkaline earth metal fluorides. The bulk and (001)-terminated surface F center ground states in BaTiO3, SrTiO3, and SrZrO3 perovskites are located 0.23, 0.69, 1.12 eV, and 0.07, 0.25, 0.93 eV, respectively, below the conduction band bottom, indicating that the F center is a shallow donor. The vacancies in BaTiO3, SrZrO3, and PbZrO3 are occupied with 1.103e, 1.25e, and 0.68e, respectively, whereas slightly smaller charges, only 1.052e, 1.10e, and 0.3e are localized inside the F center on the perovskite (001) surface. In contrast to the partly covalent ABO3 perovskites, charge is well localized (around 80 %) inside the ionic CaF2, BaF2, and SrF2 fluorine vacancy.
Key words: Ab initio calculations, F center, perovskites.