First-Principles Design of Room Temperature Ferromagnetic Metallic Rare-Earth Zintl Compounds AB₂C₂ (A = Ce, Pr, Nd;...

A comprehensive density functional theory (DFT) study investigates the structural, electronic, and magnetic properties of rare-earth Zintl compounds AB₂C₂ (A = Ce, Pr, Nd; B = Li; C = Sb). Calculations employing the FPLAPW method (WIEN2k code) utilize PBE-GGA and GGA + U approximations to accurately treat correlated 4f electrons. Structural optimization reveals ferromagnetic (FM) ordering as the most stable ground state for all compounds, with optimized lattice parameters aligning with lanthanide series trends. Electronic structure analysis confirms metallic behavior driven by rare-earth 4f and 5d states near the Fermi level. Density of states analysis shows significant hybridization between Sb-p and RE-d states, indicating covalent interactions within the anionic [Sb] networks consistent with the Zintl concept. Magnetic characterization reveals total moments localized on rare-earth sites, with strong FM exchange interactions stabilizing the ground state. Calculated Curie temperatures (T_C) from DFT + U (with U_eff  = 0.52-0.58 Ry) and empirical relations exceed room temperature, despite DFT being a 0K method, the predicted T_C  > 300 K indicates that ferromagnetic order persists under ambient conditions comparable to values reported for spintronic Heusler alloys. Negative formation and cohesive energies confirm thermodynamic stability and experimental viability. In conclusion, these compounds exhibit a promising combination of robust room-temperature ferromagnetism, metallic conductivity, and structural stability, fundamental prerequisites for spintronic materials requiring efficient spin-polarized transport, identifying these Zintl phases as compelling candidates for experimental exploration.