First-principle calculations of the electronic structure of intrinsic defects and impurities of alkali metals in SiS2

It was performed the systematic investigation of chemical modification regularities of the electronic structure at the composition changes of "ideal" SiS2 crystal by the self-consistent density functional theory method in a supercell model. It was analyzed the phases obtained during the introduction of Li and Na impurity atoms a van der Waals (vdW) space as well as during changing silicon disulfide structure due to the appearance of atomic vacancies in cation and anion sublattices (nonstoichiometry effects). The features of chemical bonding in the defect-free and defective SiS2 crystals were analyzed based on electronic density distribution maps. Electronic density maps clearly show the covalent-ionic bond nature within the chains with the predominant charge concentration on Si–S bonds as well as the weak van der Waals bond components between chains with the participation of silicon electronic lone pair.