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IJPAP Vol.44(05) [May 2006] >


Title: Lattice dynamical calculations of spinel structure compounds
Authors: Kushwaha, A K
Shankar, Girija
Kushwaha, S S
Keywords: Spinel structure
Lattice dynamics
Octahedral
Zone center
Phonons
Issue Date: May-2006
Publisher: CSIR
IPC CodeC30B
Abstract:  Lattice dynamical calculations have been performed for normal spinel structure compounds using the proposed theoretical model. In this model, the dynamical matrix is split into two parts: (i) the short range part is evaluated by using Taylor’s expansion of the crystal potential energy in the harmonic approximation and (ii) the long range part is evaluated on the basis of screened Coulomb potential. This model is applied to study the zone centre (=0) phonon frequencies of sulphide spinels MCr2S4 (M= Mn, Fe, Cd). The significant outcome of the present work is that (i) the tetrahedral M-S force constants are smaller than the respective octahedral (Cr-S) ones, (ii) the bending force constants are negligible, and (iii) the effective dynamical charges of the bivalent metal ions are nearly zero. The zone-center phonon frequencies, thus calculated using these parameters are found to be in very good agreement with the observed results.
Page(s): 385-390
ISSN: 0975-1041 (Online); 0019-5596 (Print)
Source:IJPAP Vol.44(05) [May 2006]

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