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

Abstract

This paper presents the theoretical investigation of energy levels of valence bands (VB) and core levels (CL) of the ferroelectric SbSI single crystals in antiferroelectric and ferroelectric phases. Since the best approximation for the deep VB levels is a calculation by the Hartree-Fock method, the molecular model of a SbSI crystal was used for calculations. This model of the crystal was also used for calculations of the total density of states. It was found that the VB and CL of this ferroelectric semiconductor are sensitive to the small lattice distortion at the phase transition, and that an average of the total density of states, when all atoms participate in oscillations of all normal modes, are more similar to the experimental X-ray photoelectron spectra (XPS). The experimental splitting of CL obtained by XPS was compared with the theoretically calculated one by two different methods. The cluster model calculations showed that the splitting of the CL in SbSI might be caused by photoelectron emission from the atoms, which have different valence state, at the surface.

Investigation of the electronic structure of the SbSeI cluster

“…As is seen from Fig. 4b, the theoretical total densities of states calculated for SbSI [10] and SbSeI clusters of 20 molecules are similar in the energy range of 0-25 eV.…”

“…6a and b). Therefore, the energy difference clust * ∆E of the 3d state between two Sb atoms and of the 3d state between two Se atoms at the edges of the SbSeI cluster can be estimated [10]:…”

“…In [10] we performed UFH theoretical calculations of the energies of CLs, bond orders between atoms, ionic charges of atoms, and the splitting energy using the SbSI molecular cluster. Task of the present work is UFH theoretical calculations of bond orders between atoms, ionic charges of atoms, and the splitting energy of CLs using the SbSeI molecular cluster.…”

XPS analysis of sonochemically prepared SbSI ethanogel

“…The shifts are towards higher/lower binding energies for the surface cations/anions [10]. In order to understand the splitting and the large shift of the CL binding energies several reasons were analyzed [1,9,[11][12][13][14][15][16], e.g. appearance of inequivalent positions of atoms due to domain boundaries, screening of polarization and charging effects, as well as antiparallel orientation of the chains.…”

Electronic structure of valence band of ferroelectric SbSI crystals

“…The experimental results were confirmed by the theoretical ab initio calculations. Audzijonis et al [4] performed the same theoretical calculations with the same GAMESS program and the same SbSI model as in [3] and came to similar conclusions, however without citation of [3]. The purpose of this paper is to discuss in greater details the form and electronic structure of the VB in SbSI crystals based on the XPS and on theoretical calculations.…”