Large-scale modelling of the phase transitions in KTa1-xNbxO3 perovskite solid solutions

R. I. Eglitis, D. Fuks, S. Dorfman, E. A. Kotomin, G. Borstel

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

We use quantum chemical method of the intermediate neglect of the differential overlap (INDO) based on the Hartree-Fock formalism for a large-scale modelling of the atomic and electronic structure of KNbxTa1-xO3 (KTN) perovskite solid solutions. Results for periodic defect models (large unit cell) of 40 and 320 atoms are compared with 135-atom INDO cluster calculations. Periodic Nb impurities in KTaO3 reveal clear off-center displacement beginning with the smallest calculated concentrations, so does an isolated Nb impurity in a cluster INDO calculation. The magnitude of Nb off-center displacement is close to the X-ray-absorption fine-structure observation (0.27 a.u.). In contrast, Ta impurities in KNbO3 always remain on-center, due to higher ionicity of Ta as compared to Nb atom. Using the calculated energy gain due to the off-center displacements of Nb atoms for several concentrations of Nb in KTN, we construct the non-empirical Ginzburg-Landau-type functional for the excess energy. The coefficients of this functional are concentration dependent. This dependence allows to define the type of the concentration-induced phase transition in KTaO3 alloyed by Nb.

Original languageEnglish
Pages (from-to)153-157
Number of pages5
JournalMaterials Science in Semiconductor Processing
Volume5
Issue number2-3
DOIs
StatePublished - 1 Apr 2002

Keywords

  • ABO perovskites
  • INDO method
  • KTN solid solutions

Fingerprint

Dive into the research topics of 'Large-scale modelling of the phase transitions in KTa<sub>1-x</sub>Nb<sub>x</sub>O<sub>3</sub> perovskite solid solutions'. Together they form a unique fingerprint.

Cite this