Abstract
To investigate the energy bands structure of α-Hg 3 S 2 Cl 2 , first-principles calculations were performed within the density functional theory formalism using the SIESTA software package. Using the local density approximation the atomic positions are relaxed so as to minimize the forces acting on the atoms. The analysis of band energy dispersion shows that the VBM and CBM are located at Г symmetry point, resulting in a direct energy band gap of 3.198 eV. It is established that the nature of interatomic interactions has complex character and includes covalent and ionic parts. The inclusion of spin-orbit coupling not strongly modifies the structure of energy bands.
Highlights
Hg3X2Y2 (X = S, Se, Te; Y = F, Cl, Br, I) compounds present a class of perspective materials for nonlinear optics
We have found that the conductive band is formed prevailingly from S-p/d states and Hg-s states
Considering the DOS/PDOS, one can conclude that in αHg3S2Cl2 the sulphur and chlorine atoms play more prominent role in the valence band than the mercury atoms, which is attributed to the higher electron negativity of sulphur and chlorine atoms than the mercury
Summary
Hg3X2Y2 (X = S, Se, Te; Y = F, Cl, Br, I) compounds present a class of perspective materials for nonlinear optics. Physical and chemical properties of these crystals are very useful for the creation of functional elements for optical devices. The corderoite family compounds are characterized by such optical properties as high refractive index and photoconductivity[1,2,3] and are materials showing presence of optical activity and electro-optic effect.[4,5,6,7,8,9,10] The main structural feature of mentioned crystals is the tendency to formation of various polymorphic modifications. The band structure and optical transitions of α-Hg3S2Cl2 have been investigated using DFT. The study on the origin of electronic properties provides an important information and prediction of physical properties of title crystal
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