SLIPUKHINA I. The influence of symmetry and structural factors on energy spectrum formation in the vicinity of band gap of complex semiconductors

The dissertation is devoted to the investigation of symmetry and structural factors, which are determinative in the formation of energy spectra of complex crystals and characterize their response on the external perturbations like strains and defects. In the framework of minimal band complexes concept using the empty-lattice approximation, the main aspects of CdSb crystal's band spectrum formation in the vicinity of band gap are established. Based upon the example of this semiconductor, the peculiarities of formation of minimal band complexes in the valence band are considered in the case of crystals, in unit cells of which none of the atoms are situated at the specific Wyckoff positions. The differences in formation of minimal band complexes in the band spectra of isovalent SnS and PbS crystals belonging to A4B6 group semiconductors with essentially different symmetry, as well as in their solid solution Pb0.5Sn0.5S, are studied. The effect of the shear strains on the topology of bands in the vicinityof band gap of SbSI and In4Se3 crystals is studied. The changes in the band spectrum of copper- and lithium-intercalated In4Se3 crystals are investigated by means of first-principles calculations.