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Lattice Mode Anharmonicity in Sodium Nitrite
Author(s) -
Brehat F.,
Wyncke B.,
El Sherif M.
Publication year - 1982
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.2221100216
Subject(s) - anharmonicity , phonon , dielectric , sodium nitrite , lattice (music) , condensed matter physics , infrared , chemistry , dispersion (optics) , phase transition , infrared spectroscopy , crystal structure , materials science , molecular physics , optics , physics , crystallography , optoelectronics , organic chemistry , acoustics
Abstract The anharmonicity of the infrared active lattice modes of sodium nitrite is studied from measurements of the infrared reflectivity from 60 to 400 cm −1 , in the temperature range 80 to 460 K. The infrared reflectivity spectra are analysed with the four‐parameter dispersion model based on the factorized form of the dielectric function. The comparison between the results of the quantum theory and the dependence observed of damping shows that cubic anharmonicity drives the lattice dynamics of sodium nitrite when the crystal structure is ordered, and that disorder occurs below the phase transition temperature. The results confirm the breakdown of the selection rules in the paraelectric phase and suggest the existence of dielectric dispersion in the low frequency region.