Study of intrinsic point defects in oxides of the perovskite family: I. Theory

Prosandeyev, S. A.; Fisenko, A. V.; Riabchinski, A I; Osipenko, I. A.; Raevski, I. P.; Safontseva, N. Yu.

doi:10.1088/0953-8984/8/36/021

Cited by 47 publications

(38 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These Nb atoms remain to be identical; i.e., we did not see formation of dipole moments of the Nb 1 -V O -Nb 2 type, as suggested in Ref. 25. Note that the relevant relaxation energy is several eV which is typical for many point defects in ionic and partly ionic solids.…”

Section: Discussionsupporting

confidence: 71%

First-principles and semiempirical calculations forFcenters inKNbO3

et al. 1997

View full text Add to dashboard Cite

The linear muffin-tin-orbital method combined with density functional theory (local approximation) and the semiempirical method of the intermediate neglect of the differential overlap (INDO) based on the Hartree-Fock formalism are used for the study of the F centers (O vacancy with two electrons) in cubic and orthorhombic ferroelectric KNbO3 crystals. Calculations for 39-atom supercells show that the two electrons are considerably delocalized even in the ground state of the defect. Their wave functions extend over the two Nb atoms closest to the O vacancy and over other nearby atoms. Thus, the F center in KNbO3 resembles electron defects in the partially-covalent SiO2 crystal (the so-called E ′ 1 center) rather than usual F centers in ionic crystals like MgO and alkali halides. This covalency is confirmed by the analysis of the electronic density distribution. Absorption energies were calculated by means of the INDO method using the ∆ self-consistent-field scheme after a relaxation of atoms surrounding the F center. For the orthorhombic phase three absorption bands are calculated to lie at 2.72 eV, 3.04 eV, and 3.11 eV. The first one is close to that observed under electron irradiation. For the cubic phase, stable at high temperatures, above 708 K, only the two bands, at 2.73 eV and 2.97 eV, are expected.

show abstract

Section: Discussionsupporting

confidence: 71%

First-principles and semiempirical calculations forFcenters inKNbO3

et al. 1997

View full text Add to dashboard Cite

show abstract

“…Hence, a greater number of oxygen vacancies correspond to the generation of more free electrons in CCTO ceramics. Prosandeyev et al [29] reported that ceramics become more conductive as the sintering temperature increases. Since CCTO can be regarded as a Cu-substituted CTO, the grains should become more semi-conducting as the sintering temperature increases.…”

Section: Resultsmentioning

confidence: 99%

Microstructural and electrical properties of CaTiO3–CaCu3Ti4O12 ceramics

Wang

Lin

Kao

et al. 2010

Journal of Alloys and Compounds

View full text Add to dashboard Cite

“…First, due to the lowering of the local point symmetry at the O site in ferroelectric phases of KNbO 3 (for instance, in the orthorhombic phase which is the room-temperature one), the degeneracy of the 2p-type excited state may be lifted, resulting in several splitted absorption bands. Second, there were claims in the literature in favor of the symmetry breaking between two Nb atoms neighboring the O vacancy, resulting in an asymmetric electron density distribution [6]. In order to clarify these questions and to check the assignment of the 2.7 eV absorption band, we study in the present paper the F center in KNbO 3 using the supercell model and two different theoretical techniques: the full-potential linear muffin-tin orbital (FP-LMTO) and the semiempirical Intermediate Neglect of the Differential Overlap (INDO) methods.…”

Section: Introductionmentioning

confidence: 99%

First-principles and semiempirical Hartree-Fock calculations for F centers in KNbO[sub 3] and Li impurities in KTaO[sub 3]

Eglitis¹,

Kotomin²,

Postnikov³

et al. 1998

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. The linear muffin-tin-orbital method based on the density-functional theory and the semi-empirical method of the Intermediate Neglect of the Differential Overlap based on the Hartree-Fock formalism are used for the supercell study of the F centers in cubic and orthorhombic ferroelectric KNbO 3 crystals. Two electrons are found to be considerably delocalized even in the ground state of the defect. The absorption energies were calculated by means of the INDO method using the ∆SCF scheme after a relaxation of atoms surrounding the F center.As an example of another type of point defect in perovskite, an isolated Li impurity in KTaO 3 as well as interacting Li pairs are considered in the supercell approach, using the supercells of up to 270 atoms. The off-center Li displacement, reorientational energy barriers and the lattice relaxation around impurities are calculated. The results are compared with those obtained earlier within the shell model, revealing the relaxation pattern somehow different from the shell model estimations.

show abstract

Study of intrinsic point defects in oxides of the perovskite family: I. Theory

Cited by 47 publications

References 29 publications

First-principles and semiempirical calculations forFcenters inKNbO3

First-principles and semiempirical calculations forFcenters inKNbO3

Microstructural and electrical properties of CaTiO3–CaCu3Ti4O12 ceramics

First-principles and semiempirical Hartree-Fock calculations for F centers in KNbO[sub 3] and Li impurities in KTaO[sub 3]

Contact Info

Product

Resources

About