Large-scale modelling of the phase transitions in KTa1-xNbxO3 perovskite solid solutions
Autor(en): | Eglitis, RI Fuks, D Dorfman, S Kotomin, EA Borstel, G |
Stichwörter: | ABO(3) perovskites; CENTERS; CORUNDUM CRYSTALS; DOPED KTAO3; Engineering; Engineering, Electrical & Electronic; FIRST-PRINCIPLES; HARTREE-FOCK CALCULATIONS; INDO method; KNBO3; KTN solid solutions; Materials Science; Materials Science, Multidisciplinary; PARAMETRIZATION; Physics; Physics, Applied; Physics, Condensed Matter; PRESSURE; PURE; SEMIEMPIRICAL CALCULATIONS | Erscheinungsdatum: | 2002 | Herausgeber: | ELSEVIER SCI LTD | Journal: | MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING | Volumen: | 5 | Ausgabe: | 2-3 | Startseite: | 153 | Seitenende: | 157 | Zusammenfassung: | 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 (0.27a.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. (C) 2002 Elsevier Science Ltd. All rights reserved. |
Beschreibung: | Symposium on Advanced Materials for Microelectronics held at the Spring Meeting of the E-MRS, STRASBOURG, FRANCE, JUN 18-21, 2002 |
ISSN: | 13698001 | DOI: | 10.1016/S1369-8001(02)00097-5 |
Show full item record