Investigation of the Vibration Spectra of a SbSBrxI1-x Crystal in Harmonic and Quasiharmonic Approximation

The vibration spectra of SbSBr x I 1-x (x = 0 ÷ 0.75) crystal have been determined in quasiharmonic approximation by diagonalization of dynamical matrix. Applying the model atom A with its own parameters (mass and force constant) we were able to get exact normal modes' vibration frequencies. Th...

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Bibliographic Details
Published in:Ferroelectrics 2009-11, Vol.392 (1), p.33-44
Main Authors: Audzijonis, A., Žigas, L., Kvedaravičius, A., Žaltauskas, R.
Format: Article
Language:English
Subjects:
Anharmonic lattice modes
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Lattice dynamics
Phonon states and bands, normal modes, and phonon dispersion
Phonons and vibrations in crystal lattices
Physics
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Summary:The vibration spectra of SbSBr x I 1-x (x = 0 ÷ 0.75) crystal have been determined in quasiharmonic approximation by diagonalization of dynamical matrix. Applying the model atom A with its own parameters (mass and force constant) we were able to get exact normal modes' vibration frequencies. The obtained normal modes' frequencies were superposed with experimental data. It is proved that in Brillouin zone's point k = 0 the lower frequency IR (infrared) mode of B 1u symmetry and lower frequency R (Raman) mode of B 1g symmetry are soft-alike modes whereas in Brillouin zone's point k = 0.5 an acoustic and Raman mode become active, but lower frequency IR mode becomes inactive. The interaction between phonons creates the anharmonicity of soft-alike IR, R and A vibration modes.
ISSN:0015-0193
1563-5112
DOI:10.1080/00150190903412473