Optoelectronic properties of the double perovskite Ba2TiMnO6 under applied pressure: A density functional theory study

We studied the pressure dependence of the optical properties and electronic structure of the double perovskite Ba 2 TiMnO 6 using the PBE-GGA and PBE-GGA + U exchange–correlation functionals. DFT calculations reveal direct semiconductor behaviour in Ba 2 TiMnO 6 . Hubbard correction significantly affects the electronic characteristics, shifting the O- p x and spin-up Mn- d xz orbitals to higher energies. Superexchange, which is associated with electrons jumping between the Mn-3 d and O-2 p orbitals, is responsible for the magnetic order. Furthermore, Ba 2 TiMnO 6 exhibits significant optical conductivity, high dielectric constants, and a robust light absorption coefficient in the UV energy range. This makes it a promising candidate for high-efficiency perovskite solar cells in optoelectrical applications. Discrepancies in the optical characteristics below 15 eV between the two methods are primarily due to the intraband and interband transitions of the Mn-3 d electrons. The comparison of the electronic and optical properties of two related double perovskites, Ba 2 TiMnO 6 and Ba 2 WMnO 6 show that the PDOS position of the W-5 d or Ti-3 d bands with respect to the E F governs their magnetic, electronic, and optical properties. According to the pressure effect investigation, compressive strain might produce structural distortion in Ba 2 TiMnO 6 at pressures of around 8 GPa, resulting in a significant enlargement of the semiconducting gap.