Refined geometry and frozen phonons in KNbO3

Autor(en): Postnikov, AV
Borstel, G
Stichwörter: 1ST-PRINCIPLES CALCULATIONS; density functional theory; ferroelectric instability; FERROELECTRICS; FORCE-CONSTANTS; frozen phonons; INELASTIC LIGHT-SCATTERING; KNbO3; KTAO3; LMTO; Materials Science; Materials Science, Multidisciplinary; Physics; Physics, Condensed Matter; RELAXATION MODES; SPECTROSCOPY; STRUCTURAL PHASE-TRANSITIONS; total energy
Erscheinungsdatum: 1997
Volumen: 194
Ausgabe: 1-4
Startseite: 69
Seitenende: 81
Full-potential LMTO calculations for KNbO3 reported up to now provided a reasonable description of off-center equilibrium displacements, including transversal optical Gamma phonons. However, when addressing more sensitive phonon properties and the behavior of the ferroelectric instability over the Brillouin zone, the need was realized to achieve a substantially higher level of accuracy. In order to arrive at ultimately accurate results available with the LMTO method in the local density approximation, the stability of full-potential LMTO predictions for off-center displacements in KNbO3, as depending on the choice of basis and expansion cutoffs, has been thoroughly investigated. With the calculation setup thus optimized, supercell frozen phonon calculations aimed at the study of the chain-structure instability over the Brillouin zone have been done, and the long-wavelength limit of the LO phonon is discussed.
4th Williamsburg Workshop on 1st-Principles Calculations for Ferroelectrics, WILLIAMSBURG, VA, FEB 04-07, 1996
ISSN: 00150193
DOI: 10.1080/00150199708016083

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