Pressure-Induced Electronic, Structural and Optical Properties of Ru-LiNbO₃ Perovskite: A DFT+U Study

Owing to its remarkable features, lithium niobate (LiNbO3) has been deployed in wide range of applications. In this study, the structural, electronic, and optical properties of the pristine LiNbO3 and Ru substituted B-site of LiNbO3 were investigated by employing density functional theory approach (DFT) within CASTEP code based on (GGA-PBE). Moreover, different hydrostatic pressures (0, 5, 10, 15, and 20 GPa) were applied. The results revealed that the optimized lattice parameters and energy bandgap are in well agreement with the published results. Besides, the insertion of Ru atoms at Nb site of LiNbO3 leads to a decrease in the crystal lattice constants. This reduction becomes more increased in both pure and doped structures with rising pressure. At 0 GPa, the calculated bandgap is significantly narrowed from 3.35 eV, 0.73 eV and 0 eV for LiNbO3, LiNb0.5Ru0.5O3, and LiRuO3, respectively. However, increasing pressure to 20 GPa shows a minor increase in the bandgap width of the host structure, while it is decreased in the doped compounds. The absorption spectrum at zero pressure for the host system reveals an improved in the UV region with slight absorption in the visible part. Ru substitution can effectively narrow the bandgap and increase visible-light absorption in the visible region of electromagnetic radiation. At high pressures, the absorption coefficient shifts toward the UV range, while it reduced in the visible range of Ru: LiNbO3. The current results suggest Ru-alloyed LiNbO3 as novel lead-free compounds for next-generation applications.