The dual localized-itinerant character of uranium $5f$ electrons governs the electronic and magnetic properties of many actinide materials, yet the microscopic mechanisms controlling their tunable itinerancy remain incompletely understood. Here we investigate the uranium dipnictides $\mathrm{U}{X}_2$ ($X=\mathrm{P},\mathrm{As},\mathrm{Sb}$) using fully charge-self-consistent density functional theory combined with dynamical mean-field theory including spin–orbit coupling (SOC) in the paramagnetic (PM) state at $T=300\mathrm{K}$. The calculations reveal that the uranium $5f$ shell resides in a mixed-valence configuration with occupancies $\langle n_{5f}\rangle \approx 2.6-2.8$, dominated by $5f^2-5f^3$ states. Momentum-resolved spectra and hybridization functions show that decreasing $5f-p$ hybridization along the $\mathrm{P}\to \mathrm{As}\to \mathrm{Sb}$ series enhances correlation effects and strengthens $5f$ localization, whereas hydrostatic pressure increases hybridization and quasiparticle (QP) coherence, driving the system toward greater itinerancy. The Matsubara self-energy indicates coherent Fermi-liquid behavior at 300 K with pronounced spin–orbit-driven orbital differentiation, where the $j=5/2$ manifold is more strongly renormalized than the $j=7/2$ states. Local susceptibilities reveal sizable fluctuating $5f$ moments in the PM phase at room temperature, providing a qualitative—necessarily speculative—connection to magnetic scales inferred from previous static DFT calculations of the antiferromagnetic ground state. Additional calculations for ${\mathrm{UP}}_2$ in its experimentally established tetragonal $I4/mmm$ phase show that the key features identified in the $P4/nmm$ reference structure—including the SOC-split $5f$ manifold, the dominance of $j=5/2$ states near the Fermi level, and pressure-enhanced QP coherence—remain qualitatively preserved, with only moderate quantitative differences arising from the distinct crystallographic environment. Together these results establish a clear microscopic mechanism: ligand chemistry sets the baseline uranium–ligand hybridization and degree of $5f$ localization, while pressure continuously tunes the same control parameter, providing a unified framework for understanding how correlations, SOC, and hybridization govern $5f$ itinerancy in uranium intermetallic compounds.

Close

PrevNext

View figure in article

• Density of states
• Electronic structure
• Actinides
• DFT+DMFT