The electronic potential of the V-VI-VII compounds in the region of phase transition

Physica Status Solidi (b)

Žigas²,

Siroic³

et al. 2006

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The energy levels of valence bands (VBs) and core levels (CLs) of SbSeI single crystals have been investigated theoretically. A molecular model of the SbSeI crystal was used for the calculations of VBs and CLs by the Hartree -Fock method (UHF). This molecular cluster consisting of 20 molecules was used for calculations of the total and of the averaged density of states including atom vibrations. The averaged total density of states is more similar to the experimental X-ray photoelectron spectra (XPS). The cluster-model calculations showed that the splitting of the CLs in SbSeI may be caused by photoelectron emission from the atoms at the surface which are in a different valence state.

“…The most outstanding representative of this class of compounds is SbSe x S 1-x I, x = 0 to 1 [1][2][3]. It is characterized by a number of unique properties, e.g.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the electronic structure of the SbSeI cluster

Physica Status Solidi (b)

Žigas²,

Siroic³

et al. 2006

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“…The growth rate in the directions perpendicular to the c-axis is about 10 times slower. Employing this technique, during 50-60 days one can get crystals up to the dimensions of 5 Â 5 Â 25 mm 3 . The crystal surfaces are mirror-like, the largest is the [1 1 0]-plane, and the c-axis is always directed along the crystal.…”

Section: Growing Sbsei Crystalsmentioning

confidence: 99%

“…The most outstanding representative of this class of compounds is SbSe x S 1Àx I with x ¼ 021 [1][2][3]. It is characterized by a number of unique properties, e.g.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the vibrational spectrum of SbSeI crystals in harmonic and in the anharmonic approximations

Physica B: Condensed Matter

Klingshirn

Žigas³

et al. 2007

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The reflectivity spectrum RðoÞ of SbSeI crystals was experimentally studied in the spectral range of 102300 cm À1 over a wide range of temperatures (10-297 K) with light polarization Ekc and E ? c . The spectra of optical constants and optical functions were calculated using the Kramers-Kronig and optical parameter fitting methods. The dependence of the frequencies o T and o L of the low-frequency B 1u mode (for Ekc) on temperature was obtained from the experiment. From spectra e ll ðoÞ and Imðe À1 ÞðoÞ the frequencies o L and o T of B 1u normal modes were found at temperatures 10-297 K. The frequencies of normal modes and amplitudes of normal coordinates were calculated by diagonalization of the dynamical matrix in harmonic approximation. The properties of the low-frequency B 1u mode are explained in anharmonic approximation by employing the average potential energy function V ðzÞ. The latter is strongly anharmonic and thus causes the frequency of this mode to show a quite strong temperature dependence. The interaction between phonons creates the anharmonicity of low-frequency B 1u vibrational mode. r

“…In [5,6] we proposed the method for calculating the potential energy at point r of the unit cell. This method allows determination of the potential energy at any point r in the unit cell based on standard structural data and requires no additional adjustable parameters for fitting the results to the experimental data.…”

Section: Investigation Of Potential Energy Of Sb Atoms In Anharmonic mentioning

confidence: 99%

“…For the sum in Eq. (4) we used about 5000 vectors s. The dependence of the atomic form factors f α (s) for Bi, Sb, S, Se, I, Br atoms on the modulus of the reciprocal lattice vector |s| has been published in [5]. We shall study the potential energy V p (z) of Sb atom of the B 1u (A u ) symmetry soft mode vibrations upon the amplitudes of normal coordinates or symmetry coordinates (relative displacement of atoms) along the z(c)-axis.…”

Section: Investigation Of Potential Energy Of Sb Atoms In Anharmonic mentioning

confidence: 99%

The Nature of Piezoelectricity of Ferroelectric SbSI Crystal

Žigas²,

Kvedaravičius³

2011

Ferroelectrics

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The contribution of Sb atoms soft mode to the temperature dependences of the piezoelectric modulus e(T) and atomic equilibrium position's difference z(T) has been studied theoretically, when SbSI crystal is deformed along crystallographic x(a), y(b) and z(c)-axes. The largest change of e(T) occurs in the ferrophase near the phase transition (when T ≈ T C ). At T < T C , the e(T) changes become slow. It has been found that value and anomalous temperature dependence of e(T) and z(T) is influenced by the change of mean potential energy V p (z)of Sb atoms in soft mode due to its interaction with phonons.