First-principles insights into the structural stability, spin-polarized electronic structure, and multifunctional...

A comprehensive first-principles study of actinide antimonides U₃TSb₅ [T = Cr, Mn, Ti, and V] is carried out using density functional theory to explore their structural, electronic, magnetic, mechanical, optical, phonon and thermoelectric properties. Structural optimization confirms that all compounds crystallize in a stable hexagonal phase with space group P6₃/mcm, as supported by smooth energy-volume curves fitted with the Birch-Murnaghan equation of state. Transition-metal substitution leads to moderate variations in lattice parameters and bulk modulus without altering the structural framework. Spin-polarized electronic structure calculations reveal metallic behaviour in both spin channels, with strong hybridization between U-5f and transition-metal d states dominating near the Fermi level. All compounds exhibit a ferromagnetic ground state, with uranium and transition-metal atoms contributing significantly to the total magnetic moments, particularly in U₃CrSb₅ and U₃MnSb₅. Elastic constant analysis confirms mechanical stability, while Pugh's ratio and Poisson's coefficient indicate ductile behaviour with mixed ionic-metallic bonding. Optical property analysis shows high dielectric response, strong absorption in the visible-ultraviolet region, pronounced plasmon features, and enhanced optical conductivity, reflecting their metallic character and optoelectronic potential. Thermoelectric transport calculations demonstrate increasing Seebeck coefficients and moderate figures of merit with temperature, suggesting scope for further optimization. The phonon dispersion analysis indicates that all studied U₃TSb₅ [T = Ti, V, Cr, Mn] compounds exhibit dynamical instability due to the presence of imaginary phonon modes. The results establish U₃TSb₅ compounds as structurally robust, metallic ferromagnets with multifunctional properties, offering promising prospects for spintronic, optoelectronic, and thermoelectric applications.