Speaker
Description
Uranium hydrides are not only materials necessary for an understanding of fundamental aspects of actinides. They are also relevant for nuclear technologies as well as for specific hydrogen storage tasks, e.g. storing tritium in nuclear fusion devices. The electronic structure of uranium hydrides (α- and β-UH3, UH2) reflects two contradictory tendencies. One is a charge transfer from U towards H, the other is the stability of the f shell. Here, based on the first-principle calculations we reveal the phase stability of three of them: UH2, Alfa-UH3, and Beta-UH3 with respect to the relative occupancy of the majority f-states. The transfer is thus realized in U by the 6d and 7s electrons, which become noticeably depleted, but the 5f occupancies remain high, together with the volume expansion, to pronounced ferromagnetism of the U hydrides with Curie temperatures far above 100 K. We found a relatively simple model of the electron structure that is able to correctly and still accurately model the elastic, magnetic (spin, orbital moments) properties as well, as reveal the lattice dynamics properties for further spectroscopic measurements. Theoretical calculations reveal for the first time the non-collinear ferromagnetic order of the one of Uranium sites in Beta-UH3 and allow the estimate of the Curie temperatures in reasonable agreement with the experiment[1].
References:
1. L. Kyvala, L. Havela, A. Kadzielawa, D. Legut, J. Nucl. Mater. 567, 153817 (2022), doi.org://10.1016/j.jnucmat.2022.153817
