A computational study of hydrogen doping induced metal-to-insulator transition in CaFeO₃, SrFeO₃, BaFeO₃ and SmMnO₃

The metal-to-insulator transition (MIT) in rare earth perovskite oxides has drawn significant research interest for decades to unveil the underlying physics and develop novel electronic materials. Recently, chemical doping induced MIT in SmNiO₃ has been observed experimentally, with its resistivity changed by eight orders of magnitude. The mechanism of switching from one singly occupied Ni e_g orbital to two singly occupied e_g orbitals upon doping has been proposed by experimentalists and verified by computation. Here, we tested if this mechanism can be generally applied to other perovskite oxides with non-Ni B site elements. We applied first principles density functional theory (DFT) to study a series of perovskite oxides, CaFeO₃, SrFeO₃, BaFeO₃ and SmMnO₃. We investigated the geometry and electronic structures of pure and hydrogen doped oxides. We found that pure CaFeO₃, SrFeO₃ and BaFeO₃ are metallic while pure SmMnO₃ has a small band gap of 0.69 eV. Upon hydrogen doping, band gap opening was predicted for all four oxides: HSE06 predicted band gap values of 1.58 eV, 1.40 eV, 1.20 eV and 2.55 eV for H-doped CaFeO₃, SrFeO₃, BaFeO₃ and SmMnO₃, respectively. This finding opens up research opportunities for exploring a broader range of materials for MIT to be used in optical and electronic devices.