The presence of oxygen character at the CBM suggests polar covalent Mn-O bonding with hybridised states. Since Mn and Ni dominate the CBM and VBM respectively, charge localisation would occur on Mn (for electron polarons) and Ni (for hole polarons). The Mn 3d states in the spin-up channel at the CBM also suggest that Mn would adopt a highspin configuration when an additional electron is populated to form Mn 3+ (d 4 ). Liu et al. Figure shows the electronic band structure and both functionals show weak band dispersion, reflecting strong electron-electron correlations. LMNO is calculated to be a widegap semiconductor, with an indirect band gap of 1.76 and 3.17 eV determined using PBEsol + U and HSE06 functionals, respectively. The hybrid approach, in theory, should give a more reliable prediction of fundamental band gap compared to PBEsol+U , in which the magnitude of the band gap is influenced by the choice of U values. There is limited experimental data on the fundamental band gap to compare with the current study, though an optical gap between 1.2-1.3 eV has been reported experimentally. The large difference between the fundamental and optical band gaps is likely due to the strong excitonic effects in flat d-band wide gap materials. Phase stability