Electronic Potentials of Normal Vibrational Modes in SbSI crystals

Bibliogr. str. galeSymmetry and normal coordinates of vibrational modes are calculated in both para- and ferroelectric phases of SbSI crystalsVilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Theoretical Investigation of the Electronic Structure of Ferroelectric SbSBr Molecular Cluster

This paper presents the theoretical calculation of energy levels of the valence bands and bond orders of the SbSBr single crystals using the molecular cluster model consisting twenty SbSBr molecules. The theoretical calculation revealed that the ferroelectric phase transition changes the bond orders and shift valence bands. Results of theoretical calculations of averaged total density of states of SbSBr molecular cluster are compared with the experimentally results of X-ray photoelectron spectroscopy (XPS) of SbSI crystals, because that SbSI and SbSBr crystals have isomorphic electronic structureVilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Research of the vibrational spectra of SbSI type crystals

Bibliogr. str. galeA method based on the simplified model of elementary cel and Born-van-Karman cycle condition has been applied for the investigation of vibrational spectra of SbSI type crystals. Frequencies and normal co-ordinates of vibrations along the z(c) axsis in SbSI type crystals, when k=0 and T=308 K, have been calculatedVilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Splitting of the XPS in ferroelectric SbBr crystals

Vilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Investigation of the electronic structure of the SbSeI cluster

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 stateVilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Research of the phase transition in crystals SbSBrxI1-x

Bibliogr. str. galeVilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Theoretical investigation of the electronic structure of a ferroelectric SbSI cluster at a phase transition

Bibliogr. str. galeVilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Investigation of the soft mode of SbSBrxI1-x crystals

Bibliogr. str. galeVilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Electronic structure of the BiSI cluster

The energy levels of valence bands (VB) and core levels (CL) of the BiSI crystals have been investigated theoretically. The molecular model of this crystal was used for calculation of VB and CL by the unrestricted Hartree–Fock method using GAMESS program, with Hw and MINI basis set. The molecular cluster consisting of 20 molecules of BiSI was used for calculations of averaged total density of states including atom vibrations. The spectra of averaged total density of states from VB of BiSI cluster has been compared with experimental X-ray photoelectron spectra (XPS) of VB of SbSI crystal. The results clarify that the atomic vibrations is one of possible reasons for the smoother appearance of the experimental XPS. The investigation of vibrational spectrum reveals new experimental information about the reflection spectrum of BiSI crystals. The cluster model calculations have shown that the splitting of the CL in the BiSI may be caused by the photoelectron emission from the atoms at the surface that is in different valence states. The cluster model calculation showed that splitting energy of CL depends on difference of ionic charges of the same atoms at the edges of BiSI clusterVilniaus universiteto Teorinės fizikos ir astronomijos institutasVytauto Didžiojo universitetasŠvietimo akademij

Investigation of the electronic structure of the SbSeBr cluster

The energy levels of valence bands (VB) in SbSeBr crystals were calculated for investigation of the photoelectron emission spectra of A(5)B(6)C(7) - type crystals. The molecular model of this crystal was used for calculation of VB by the Density Functional Theory (DFT) and Unrestricted Hartree - Fock (UHF) methods. The molecular cluster consisting of 20 molecules of SbSeBr was used for calculations of averaged total density of states including atom vibrations. The spectra of averaged total density of states from VB in the SbSeBr cluster were compared with experimental photoelectron emission spectra from VB of A(5)B(6)C(7) - type crystals. The results of comparison clarify that the atomic vibrations are one of possible reasons for the smoother appearance of the experimental X-ray photoelectron spectrum (XPS)