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Phonon Modes in a Disordered Lattice
Author(s) -
Chakrabarti B. K.,
Roy G. K.,
Sinha S. K.
Publication year - 1980
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.2220990130
Subject(s) - phonon , condensed matter physics , degenerate energy levels , dispersion relation , lattice (music) , impurity , physics , normal mode , lattice vibration , long wavelength limit , materials science , quantum mechanics , vibration , acoustics
The vibrational excitations are studied using the lattice Green function expansion for a disordered simple cubic system with degenerate modes. Both mass and force constant disorders are considered. The resulting dispersion relation, including damping, of the long wavelength longitudinal phonon modes are obtained in the limit of small impurity concentrations. The results are obtained analytically and are exact up to the linear term in concentration. In a simple mass defect case, the results reduce to those obtained by Langer.