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Lattice Dynamics Model of KNO 3 in Its Ferroelectric Phase
Author(s) -
Teng M. K.
Publication year - 1970
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.19700400223
Subject(s) - ferroelectricity , raman spectroscopy , condensed matter physics , phase transition , softening , lattice (music) , soft modes , materials science , statistical physics , physics , optics , dielectric , acoustics , optoelectronics , composite material
In order to study the lattice dynamics behaviour of KNO 3 through the ferroelectric I → III transition, a model is proposed for the ferroelectric phase III. The frequencies of the three normal low frequency modes are calculated and compared with Raman data. Good agreement between calculated and observed frequencies is obtained. Furthermore, basing on the proposed model, it is suggested that in the I → III ferroelectric transition, the long range electrostatic force, which represents the principal contribution for a softening of the unstable mode, shows only a small temperature dependence in accordance with experimental Raman results.