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Lattice Dynamics of Cs 2 HgBr 4 Crystal in High‐Temperature Phase
Author(s) -
Shchur Ya.I.
Publication year - 1999
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/(sici)1521-3951(199910)215:2<963::aid-pssb963>3.0.co;2-1
Subject(s) - brillouin zone , phonon , condensed matter physics , phase transition , raman spectroscopy , raman scattering , coulomb , dispersion relation , lattice (music) , physics , quantum mechanics , acoustics , electron
In order to interpret the experimental observations of Raman scattering a lattice‐dynamical modeling was carried out. A model based on an atom–atom potential function comprised of the Coulomb, short‐range and covalent interactions was used to calculate the phonon dispersion relations in Cs 2 HgBr 4 . Comparison of the calculated phonon frequencies with the experimental ones reveals a reasonable agreement for most of them. Details of the eigenvector analysis of Raman active modes and LO–TO splittings of polar modes are presented. The possible reasons for the observed incommensurate phase transition have been explained on the basis of interphonon interaction of low‐lying Σ 2 branches. The possibility of incommensurate phase transition owing to softening of the lowest Σ 2 phonon branch (A u symmetry at the Brillouin zone centre) is discussed.