Investigation of the Vibrational Spectra of a SbSI (Sb2S3)0.15 Crystals in Harmonic and Anharmonic Approximations

Author: Audzijonis Algirdas  

Publisher: Taylor & Francis Ltd

ISSN: 0015-0193

Source: Ferroelectrics, Vol.377, Iss.1, 2008-01, pp. : 22-35

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Abstract

The vibrational spectra of SbSI (Sb2S3)0.15 crystals in harmonic and anharmonic approximations are calculated by Density Functional Theory (DFT) method. Investigation of IR, R and A low frequency normal modes at points k = 0 and k = 0.5 of the Brillouin zone in SbSI (Sb2S3)0.15 crystals reveal that soft behavior of these modes mainly depends on the temperature dependent force constant Cij between Sb and I atoms and symmetry coordinates. Investigation of the mean value potential energy [image omitted]p(z) per one atom dependence on the amplitude of the soft mode B1u symmetry coordinates in c (z) axis direction on the phase transition region have explained why ferroelectric phase transition temperature TC depends on compression in x-y plane of the SbSI chains in SbSI (Sb2S3)x crystals.