Optoelectronic, magnetic, EFG and NMR properties of olivine-type LiMPO4 (M = Fe, Mn, Co, Mg) cathodes for application in lithium-ion battery by DFT

In this study, we present a comprehensive first-principles investigation into the structural, electronic, optical, magnetic, and hyperfine properties of olivine-type LiMPO₄ compounds (M =Co, Fe, Mg, Mn), using the full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). All compounds crystallize in the orthorhombic Pnma space group, with structural parameters exhibiting systematic variation according to the ionic radius of the M−site cation. Electronic band structure analysis reveals insulating behavior in LiFePO₄ and LiMgPO₄ with wide band gap, while LiCoPO₄ and LiMnPO₄ are identified as wide-bandgap semiconductors, owing to transition metal 3d–O 2p hybridization. Optical studies demonstrate pronounced anisotropy in dielectric response and absorption spectra, with LiMgPO₄ exhibiting the highest absorption threshold. Spin-polarized calculations unveil high-spin magnetic configurations in transition-metal-based compounds, with total cell magnetic moments. Furthermore, hyperfine interaction analysis, including electric field gradients and magnetic shielding tensors, and highlights significant anisotropy effects, particularly for Fe2⁺ and Mn2⁺ centers. The quadrupole coupling constants (C_Q) and asymmetry parameters (η) provide insights into local symmetry breaking and electron density distribution around metal centers. This integrated computational approach underscores the tunability of LiMPO₄ compounds for next-generation lithium-ion battery cathodes and multifunctional materials with optoelectronic and magnetic properties.