Investigation of Structural, Mechanical, Optoelectronic, and Thermoelectric Properties of BaXF ₃ (X = Co, Ir) Fluoro-Perovskites: Promising Materials for Optoelectronic and Thermoelectric Applications

Abstract

Coded within Wien2K, we carry out DFT-based calculations for investigations of the structural, elastic, optoelectronic, and thermoelectric properties of BaXF ₃ (X = Co, Ir) fluoro-perovskites. The Birch–Murnaghan fit to the energy-vs-volume data and formation energy shows that these fluoro-perovskites are structurally stable. The phonon calculation confirms the thermodynamic stability, while the relation between elastic constants such as C ₁₁ – C ₁₂ > 0, C ₁₁ > 0, C ₁₁ + 2 C ₁₂ > 0, and B > 0 validates the mechanical stability of the compounds. BaIrF ₃ exhibits a strong ability to endure compressive and shear stresses. BaCoF ₃ shows a weaker capacity of withstanding changes in volume, attributed to a lower bulk modulus. Demonstrating a higher G-modulus of rigidity than the BaIrF ₃, BaCoF ₃ demonstrates stronger resistance to change the shape and both compounds are found to be anisotropic and brittle. The determined band structure profiles reveal that both BaCoF ₃ and BaIrF ₃ demonstrate a metallic nature. In addition, the metallic nature of BaCoF ₃ and BaIrF ₃ is reinforced by the density-of-states (DOS) study, where Co and F atoms contribute significantly to the total DOS in the valence band in the case of BaCoF ₃, while that of BaIrF ₃ is predominated by the Ba and F atoms. The computed values of ε ₁(0) for BaCoF ₃ and BaIrF ₃ are approximately 30 and 19, respectively, which are in line with Penn’s model. The researched materials are confirmed to be strong contenders for optoelectronics by the lack of absorption in the visible range. For their potential use in thermoelectric device applications, thermoelectric parameters such as temperature-dependent Seebeck coefficient, specific heat capacity, thermal conductivity, power factor, and figure of merit are also investigated, which show that these materials are thermally stable and promising for applications in thermoelectric devices.