DFT study of a single F center in cubic SrTiO₃ perovskite

Abstract

ABSTRACT:Various properties of a cubic phase of SrTiO 3 perovskite containing single F centers (neutral oxygen vacancies), including energies of their formation and migration, were simulated using different formalisms of density functional theory (DFT) as implemented into CRYSTAL-2003 and VASP computer codes. The lattice relaxation around the F center was found to be sensitive to both shape and size of supercells used. The larger the supercell, the closer the defect energy level in the bandgap lies to the conduction band bottom. It approaches the optical ionization energy of 0.49 eV for 270-and 320-atom supercells, where the distance between neighboring defects increases up to four lattice constants. The defect bandwidth decreases for these supercells down to 0.02 eV, i.e., the defect-defect interaction becomes negligible. Thus, the two different first-principles periodic approaches combined provide results that are converged with respect to the supercell size and correspond to a single defect limit.

Defect States Induced by Oxygen Vacancies in Cubic SrTiO3: First-Principles Calculations

“…10,[12][13][14][15][16][17][18] Here we briefly summarize the previous results and illustrate schematically possible electronic configurations of V O in Fig. 1.…”

“…21) This may be the reason why two free carriers are [12][13][14][15] and the LDA+U calculations in ref. 10 produced in the conduction band by an O vacancy.…”

“…1. The density functional theory (DFT) calculations [12][13][14][15] with the local density approximation (LDA) and the generalized gradient approximation (GGA) have predicted that V O induces only a delocalized state with the character of 3d-t 2g orbital in the conduction band, as shown in Fig. 1(a).…”

Influence of F centres on structural and electronic properties of AlN single-walled nanotubes

“…Use of a supercell model for point defect simulation means, in fact, consideration of a 'new periodic system' with an artificially introduced periodicity. The periodicity of the point defect is defined by the choice of supercell lattice, with the space group of the defective crystal defined by the defect local point symmetry [31]. The new Brillouin zone (BZ) is smaller than the primitive one and may also differ in symmetry, when the lattice type is changed.…”

Electronic structure of defects in Sr2MgSi2O7:Eu2+,La3+ persistent luminescence material

“…Both isolated defect species [6][7][8][9][10][11][12][13][14][15][16][17][18][19] and defect aggregates [20][21][22] have been studied in simple oxide materials (e.g. CaO, MgO and TiO 2 ) with density functional theory (DFT) calculations.…”