Electronic Structure and Properties of Uranium Nitride: A Computational Study

Uranium-based compounds exhibit rich correlated-electron physics, underpinned by the interplay between itinerant and localized 5f electrons, strong spin–orbit coupling, and heavy-fermion effects. These features are central to their applications in superconductivity and nuclear fuels. In this work, we investigate the anomalous bad-metallic transport observed in uranium mononitride (UN), a key nuclear fuel material. Combining density functional theory and dynamical mean-field theory, we demonstrate that UN is a strongly correlated bad metal. Our calculations reveal that intra-atomic Hund’s exchange between the 5$f$ electrons is the primary correlation mechanism, aligning local moments and yielding large quasiparticle mass enhancements. This establishes UN as a 5f analog of a Hund’s metal, a concept typically associated with transition-metal $d$-electron systems. Our findings prompt a broader reconsideration of how Mott, Kondo, and Hund correlations interact in actinide materials.