Discovery of High‐Performance Multifunctional Zintl Compounds: Ab Initio Investigation of UCu 2 P 2 and UCu 2 As 2 for Thermoelectric and Optoelectronic Applications

ABSTRACT High‐performance multifunctional materials are key to sustainable energy technologies. This first‐principles study investigates uranium‐based Zintl compounds UCu 2 X 2 (X = P, As) for energy harvesting and optoelectronics. Structural stability in the trigonal P3̅m1 space group is confirmed using GGA. Electronic properties with the mBJ potential reveal half‐metallic character and indirect band gaps of ∼0.7 eV in the semiconducting spin channel. Optical conductivities reach 8643 Ω − 1 cm − 1 (UCu 2 P 2 ) and 7623 Ω − 1 cm − 1 (UCu 2 As 2 ). Thermoelectric transport, evaluated under the constant relaxation time approximation, includes both electronic and lattice thermal conductivities. Lattice thermal conductivity decreases with temperature due to enhanced phonon–phonon scattering; UCu 2 As 2 shows lower values from larger atomic mass and stronger anharmonicity. The figure of merit ZT peaks at ∼1.0 near 150–200 K in the spin‐down channel of UCu 2 P 2 , indicating promising low‐temperature thermoelectric performance for waste heat recovery and cooling. The combination of half‐metallicity, strong optical response, and competitive ZT positions UCu 2 X 2 as a candidate class for spintronic, optoelectronic, and energy conversion devices. Experimental validation is strongly encouraged, particularly regarding half‐metallic robustness against defects and finite temperatures, along with direct lattice thermal conductivity measurements.