Self-ordered second-component clusters in solid solutions on the basis of ferroelectric perovskites:: Nb clusters in KTaO3.

被引：5

作者：

Eglitis, RI ^{[1
]}

Vikhnin, VS ^{[1
]}

Markovin, PA ^{[1
]}

Borstel, G ^{[1
]}

机构：

[1] Univ Osnabruck, Fachbereich Phys, D-49069 Osnabruck, Germany

来源：

FIRST-PRINCIPLES CALCULATIONS FOR FERROELECTRICS | 1998年 / 436期

关键词：

perovskites; ferroelectric phase transitions; clusters; solid solutions; KTaO3; semi-empirical Hartree-Fock calculations; phase transitions;

D O I：

10.1063/1.56284

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

Semi-empirical Hartree-Fock calculations using the intermediate neglect of differential overlap (INDO) method, for self-ordered cubic symmetry clusters of seven Nb ions in KTaO3 are performed with the aim of verifying the cluster model [1] of second component-induced phase transitions in ferroelectric perovskite matrices. It is shown that such a seven-particle cluster in KTaO3:Nb has two types of quasidegenerate states of different nature. Namely, the state with the equilibrium full-symmetric dilatation and off-center displacements in [111]-directions of the central Nb-ion in the cluster, and the state with the equilibrium full-symmetric compression without any off-center effect. The consequencies of such cluster structures on the multi-well potential are discussed. In particular, an avalanche-like behaviour of the temperature dependence of the ferroelectric order parameter is obtained. The results of semi-empirical INDO calculations of a seven-impurities cluster of Nb-ions in KTaO3 confirm the key assumptions of the cluster model of induced phase transitions.

引用

页码：87 / 95

页数：9

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