Correlation Effects on Magnetic Structure and Lattice Dynamics of LaMn₇O₁₂: A First-Principles Study

LaMn₇O₁₂, a quadruple perovskite oxide (AA'₃B₄O₁₂-type), has attracted attention for its notable bifunctional activity in oxygen evolution and reduction reactions. Here, we systematically investigate the magnetic phase diagram and lattice dynamics of LaMn₇O₁₂ using two density functional theory plus Hubbard U (DFT + U) approaches: the spin-density and the charge-only-density formalism. Phase diagram analysis as a function of U and J shows that both methods stabilize the experimentally observed antiferromagnetic (AFM) configuration (C-type AFM at the B-site and ferrimagnetic structure at the A'-site Mn ions) at U = 3.5 eV and J = 0.8 eV. These U and J values are consistent with those obtained from the constrained random phase approximation. Furthermore, we observe the dynamical stability of the AFM phase through phonon dispersion curves and analyze the Raman-active phonon modes. These results highlight the critical role of appropriate U and J parameters in accurately describing the properties of LaMn₇O₁₂.