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
E-mail: rieglitis@gmail.com popov@latnet.lv
pos Анотація:1664

Received August 23, 2020, published online October 21, 2020

Abstract

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.

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