Band structure study of pure and doped anatase titanium dioxide (TiO₂) using first-principle-calculations: role of atomic mass of transition metal elements (TME) on band gap reduction

The titanium dioxide (TiO₂) semiconductor's wide band gap property restricts its application in a variety of fields. To ensure cost-effectiveness and time efficiency, researchers emphasized material modeling and theoretical analysis. This study employs a Density Functional Theory approach to investigate how the presence of transition metal elements (TME) like rhodium (Rh) and rhenium (Re) affects the optoelectronic properties of TiO₂. The study was carried out using the VASP software package and the plane-wave pseudopotential technique. The formation energy, electronic band structure, and optical properties of TiO₂ were affected by the addition of both Rh and Re as doping materials. The outcomes of the band structure and total density of states (TDOS), point out notable alterations in the energy gap (E_g) of TiO₂. The plot of the band structure illustrates that the introduction of Re leads to a more substantial reduction in the TiO₂ band gap compared to Rh. The introduction of numerous sub-states into the band gap causes the valence band to approach the conduction band at the Gamma point. The band gap reduction caused by the addition of Rh and Re TME is confirmed by the relocation of the TDOS to lower energies in the doped TiO₂ structure. Furthermore, significant changes in the partial density of states of TiO₂ upon Re doping have been observed at the bottom of the conduction band, highlighting the effectiveness of Re doping in modifying the electronic band structure of TiO₂. The outcomes of band structure and TDOS proved that TME with high atomic mass is certain to decrease TiO₂'s band gap to the range required for usage as a photocatalytic material. Rh and Re doping in TiO₂ alter their optical properties, making them suitable for optoelectronic devices.