Anion substitution and influence of sulfur on the crystal structures, phase transitions, and electronic properties of mixed TiO₂/TiS₂ compounds

Recent studies of TiO₂/TiS₂ nanostructures with various morphologies have been reported, usually showing improved properties with applications from electronics and catalysis to solar cells and medicine. However, there is a limited number of studies on the crystal structures of TiO₂/TiS₂ compounds with corresponding properties. In this research, relevant crystal structures of TiO_1–xS_x (x = 0, 0.25, 0.5, 0.75 and 1) solid solutions were investigated using an ab initio method. For each composition, crystal structures adopting anatase, rutile and CdI₂ structure type were calculated on LDA-PZ and GGA-PBE levels of theory. Novel phase transitions and predicted structures are presented, and apart from several interesting metastable structures, a very interesting pressure-induced phase transition is found in the TiOS compound. Furthermore, electronic properties were studied through the dependence of semiconducting properties on dopant concentration. The first description of the electronic properties of the mixed TiO_1–xS_x compounds in crystal form has been presented, followed by a detailed study of the structure–property relationship, which will possibly have numerous industrial and technological applications.