Structural phase transition of G-type antiferromagnetic SrMnO3 under pressure

Abstract Perovskite SrMnO 3 is a versatile material with applications in transistors, supercapacitors, and spintronic devices. This study employs the DFT+ U calculations to investigate the electronic and magnetic properties of two polymorphs: 4 H -SrMnO 3 and 3 C -SrMnO 3 under isotropic pressure conditions up to 60 GPa. A novel approach based on density functional perturbation theory (DFPT) is employed to precisely determine the on-site Hubbard U value, yielding a computed value of 4.552 eV, consistent with experimental reports. Below P = 14 GPa, the G -AFM phase of 4 H -SrMnO 3 is the most favored stable, and transitioning to the G -AFM phase of 3 C -SrMnO 3 beyond 14 GPa. Notably, we observed significant changes in the band gaps, exhibiting an increasing trend under isotropic pressure, while the magnetic moments of the Mn sites exhibit a decreasing trend from ≈2.8 μ B to ≈2.3 μ B for P = 0 GPa and 60 GPa, respectively. The projected density of states (PDOS) reveals the p - d hybridization contributions between the 3 d -Mn and 2 p -O covalent bonds, along with d - d Mott Hubbard interactions within the localized 3 d orbitals of neighboring Mn-Mn atoms. Furthermore, a decrease in the Mn1-O-Mn2 distance prompts enhanced charge transfer which was facilitated by ligand holes, leading to a noticeable decrease in the magnetic moment of the Mn site in the G -AFM phase of SrMnO 3 .