Investigation of Electronic, Optical and Thermoelectric Properties of Perovskite BaTMO₃ (TM=Zr, Hf): First-Principles Calculations

The structural, electronic, optical, and thermoelectric characteristics of crystalline oxides-perovskites BaTMO₃ (TM=Zr or Hf) were investigated using the all-electron full-potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT). The GGA as parameterized in Perdew, Burke, and Ernzerhof (PBE-GGA) was employed to calculate exchange-correlation potential. Also, the modified Becke Johnson exchange potential approximation as parameterized by Tarn and Blaha (TB-mBJ) was used to improve the bandgap estimation. According to the researchers’ calculations, the two perovskites BaZrO₃ and BaHfO₃ show insulator behavior and have widely indirect band-gap energy (R-Γ) 4.42 (3.39) eV for BaZrO₃ and 5.25 (3.69) eV for BaHfO₃ from both approaches, TB-mBJ (PBE-GGA), respectively. The optical properties such as dielectric tensor, the refractive index, the absorption coefficient, and the electron loss function have been calculated and analyzed. The optical transitions mainly take place if an electron radiate from the initial state O-2p to the final state Hf-5d or to the Zr-4d in BaHfO₃ or BaZrO₃ case, respectively. Furthermore, the transport characteristics calculations based on semi-classical Boltzmann theory have been discussed.