Phonon Thermal Transport in Uranium Dioxide—A Self-Consistent Perturbation Theory Approach

Computing thermal transport in uranium dioxide (UO₂) remains a formidable challenge for first-principles approache due to the challenges associated with Mott physics. Here we use DFT+U to explore the thermal transport properties, and apply f-orbital occupation matrix control to navigate the many metastable electronic states. Furthermore, irreducible derivative approaches are applied to compute the cubic and quartic phonon interactions in UO₂, with enhanced thermal transport computations by evaluating the phonon Green’s function via self-consistent diagrammatic perturbation theory. Our predicted phonon scattering functions and phonon lifetimes at T = 600 K agree well with our inelastic neutron scattering measurements across the entire Brillouin zone, and our thermal conductivity predictions agree well with previous measurements. Nontrivial effects on thermal tranposrt from thermal expansion, interband phonon transitions, and self-consistent contributions are also yielded in UO₂ at high temperatures.