Seaborg Institutes: Emerging Topics in Actinide Materials and Science: Panel/Actinide Physics
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: J. Rory Kennedy, Idaho National Laboratory; Taylor Jacobs, Helion Energy; Krzysztof Gofryk, Idaho National Laboratory; Assel Aitkaliyeva, University of Florida; Don Wood, Idaho National Laboratory
Monday 2:00 PM
March 20, 2023
Room: 28A
Location: SDCC
Session Chair: Krzysztof Gofryk, Idaho National Laboratory
2:00 PM Panel Discussion
3:30 PM Break
3:50 PM Cancelled
The Central Role of f-electron Correlations in the Spin Triplet Superconductor UTe2: Nicholas Butch1; 1University of Maryland
Uranium ditelluride hosts an unusual form of superconductivity. This electronic phase exhibits experimental signatures of spin-triplet pairing, multiple order parameters, time-reversal symmetry breaking, and in-gap chiral surface states, making it a leading candidate for topological superconductivity. The superconductivity emerges from a background of heavy fermion liquid, with several telltale signatures. Additional reentrant superconductivity appears at fields greater than 40T, up to at 65T, challenging theoretical understanding. These phases are readily modified by relatively modest applied pressure, eventually yielding to magnetic order. I will give an overview of current understanding of this material and discuss outstanding questions.
4:20 PM Invited
DFT+U in Uranium Dioxide: Occupation Matrix Control and Phonons: Shuxiang Zhou1; Hao Ma2; Enda Xiao3; Krzysztof Gofryk1; Chao Jiang1; Michael Manley2; David Hurley1; Chris Marianetti3; 1Idaho National Laboratory; 2Oak Ridge National Laboratory; 3Columbia University
UO2 remains a formidable challenge for first-principles due to the complex interplay among spin-orbit coupling, Mott physics, magnetic ordering, and crystal distortions. Here we use DFT+U to explore UO2 at 0K, incorporating all the aforementioned phenomena. The technical challenge is to navigate the metastable electronic states in DFT+U, which is accomplished using f-orbital occupation matrix control to search for the ground state. We find an unreported occupation matrix, in which the oxygen cage distortion of the 3k antiferromagnetic state is in excellent agreement with experiments, and both the spin-orbit coupling and the Hubbard U are critical ingredients. We demonstrate that only select phonon modes have a strong dependence on the Hubbard U, whereas magnetic ordering has only a small influence. We measure the phonon dispersion using inelastic neutron scattering, and our calculations show good agreement. The quantitative success of DFT+U warrants exploration of thermal transport within this level of theory.
4:50 PM
Synthesis, Characterization, and Magnetic Property Measurements of Some A2M4U6S17 (A = K, Rb, Cs; M = Pd, Pt) and Ba3MUQ6 ( M = transition metal; Q = S, Se) Compounds: Logan Breton1; 1University of South Carolina
Uranium chalcogenides have a unique ability to stabilize uranium’s paramagnetic 4+ oxidation state, making it possible to study the magnetic behavior of uranium(IV). However, the high oxophilicity of uranium inevitably leads to the reaction of uranium with even trace amounts of oxygen present, resulting in uranium oxide or magnetic oxychalcogenide impurities that complicate magnetic measurements. Our recently established boron−chalcogen mixture (BCM) method permits the synthesis of uranium chalcogenides starting from oxide reagents by adding a mixture of boron and the desired chalcogen to the reagent mixture, resulting in products devoid of actinide oxide or oxychalcogenide impurities. This talk will introduce the BCM method and describe the synthesis, characterization, and magnetic properties of some A2M4U6S17 (A = K, Rb, Cs; M = Pd, Pt) compounds and 2H perovskite related uranium chalcogenides with the chemical formula Ba3MUQ6 ( M = transition metal; Q = S, Se), all synthesized utilizing the BCM method.