FERROELECTRIC STRUCTURE OF KNBO3 AND KTAO3 FROM 1ST-PRINCIPLES CALCULATIONS

Autor(en): POSTNIKOV, AV
NEUMANN, T
BORSTEL, G
METHFESSEL, M
Stichwörter: CHARGE; DYNAMICS; Materials Science; Materials Science, Multidisciplinary; ORIGIN; PHASE-TRANSITIONS; Physics; Physics, Applied; Physics, Condensed Matter; TOTAL-ENERGY
Erscheinungsdatum: 1993
Herausgeber: AMER PHYSICAL SOC
Journal: PHYSICAL REVIEW B
Volumen: 48
Ausgabe: 9
Startseite: 5910
Seitenende: 5918
Zusammenfassung: 
Based on the results of total-energy calculations u sing the full-potential linear muffin-tin orbital method, the equilibrium ground-state structure is determined in perovskite-type KNbO3 and KTaO3 complex oxides. The first compound is found to have a ferroelectric zero-temperature ground state, induced by atomic displacements along [111], as is consistent with the experimentally determined low-temperature crystal structure. The displacements along [001] give rise to another ferroelectric structure which is stable in the constrained tetragonal symmetry; this structure, however, corresponds to a saddle point on a more general path connecting two adjacent [111]-type displacements. KTaO3 was found to be stable in the undistorted cubic phase at zero temperature, exhibiting a soft phonon mode, but it can be driven to a ferroelectric state by negative pressure.
ISSN: 24699950
DOI: 10.1103/PhysRevB.48.5910

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