DFT Analysis of Ba₂NbRhO₆: A Promising Double Perovskite for Sustainable Energy Applications

Our study employed the full-potential linearized augmented plane wave (FP-LAPW) approach within the density functional theory (DFT) framework to examine the fundamental characteristics of the Ba₂NbRhO₆ double perovskite. Our computed results align well with experimental measurements. The phonon dispersion relation confirmed the thermodynamic stability of Ba₂NbRhO₆, showing positive frequencies throughout. Structurally, the material is dominantly covalently bonded and mechanically predicted to be brittle. Electronic property analysis revealed an indirect band gap of 1.83 eV. The optical properties indicated a significant response in the ultraviolet and visible light spectra, with an absorption coefficient peaking at 200 × 10⁴ cm⁻¹ at 12 eV, an optical conductivity reaching up to 7575 \({\Omega }^{-1}{\text{cm}}^{-1}\) ${\mathrm{\Omega }}^{-1}{\text{cm}}^{-1}$ at 5.35 eV, and a refractive index peaking at 3.3 at 3.4 eV. The material also exhibited a reflectivity of 0.74 at 13.5 eV. Thermoelectric properties, including power factor, electrical conductivity, and Seebeck coefficient, were also determined, with a notable Figure of Merit of 0.76 at room temperature and a power factor of 84.43 W K⁻² m⁻¹ s⁻¹ at 700 K. These results suggest that Ba₂NbRhO₆ has considerable potential for application in thermoelectric devices.