Local Structure and Magnetism of La1-xMxPO4 (M=Sm, 239Pu, 241Am) Explained by Experimental and Computational Analyses

With their high chemical and self-irradiation stability, crystalline monazites are among the most promising materials for the encapsulation of nuclear wastes. Yet, the local and magnetic structures of the matrices doped with low-content actinide cation, depicted as most resistant, are still unclear. This limits the development of theoretical approaches predicting their behavior under extreme conditions--self-irradiation and long-term leaching. Here, we characterize the model matrices La1−xMxPO4 (0 ≤ x ≤ 0.10)-- with M = Sm, 239Pu, 241Am -- by X-ray diffraction and solid-state 31P NMR. As an example, we confirm that La0.96241Am0.04PO4 has higher self-irradiation resistance compared to 241AmPO4. Further, computational analyses show that magnetic properties of the Pu complex are strongly affected by the J-mixing and the paramagnetic NMR shifts are dominated by the Fermi contact contribution, arising from delocalization of the spin density of the cation toward the phosphorus through the bonds.

MARTEL Laura;  ISLAM Md. Ashraful;  POPA Karin;  VIGIER Jean-Francois;  COLINEAU Eric;  BOLVIN Hélène;  GRIVEAU Jean-Christophe; 

2021-11-03

AMER CHEMICAL SOC

JRC125009

1932-7447 (online),   

https://doi.org/10.1021/acs.jpcc.1c03957,    https://publications.jrc.ec.europa.eu/repository/handle/JRC125009,   

10.1021/acs.jpcc.1c03957 (online),