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MREI‐model calculations of Raman‐active modes in layered mixed crystals TiS 2− x Se x (0≤ x ≤2)
Author(s) -
Garg A. K.
Publication year - 2008
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1842
Subject(s) - raman spectroscopy , chemistry , phase transition , work (physics) , crystal (programming language) , phase (matter) , thermodynamics , analytical chemistry (journal) , wavenumber , electrical resistivity and conductivity , force constant , physics , molecule , optics , quantum mechanics , organic chemistry , chromatography , computer science , programming language
A modified random‐element isodisplacement model has been developed and used to calculate the concentration dependence of the wavenumbers of Raman‐active modes in mixed crystal system, TiS 2− x Se x (0≤ x ≤2). Earlier theoretical work, based on the Jaswal model, predicted a phase transition in this system on cooling up to 125 K temperature for the composition x ≥ 1.2. But recently reported resistivity measurements did not find the existence of any phase transition for a composition x < 1.4 on cooling. Our calculations show these findings and give remarkably better fitting to Raman data. The estimated values of the force constants are found to lie generally in the range 10 5 –10 6 amu cm −2 . Copyright © 2007 John Wiley & Sons, Ltd.