Aqueous Speciation of Tetravalent Actinides in the Presences of Chloride and Nitrate Ligands

14 June 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Speciation of hexachloride tetravalent uranium, neptunium, and plutonium species in aqueous media have been investigated using density functional theory in the presence of inner sphere ligands such as chloride, nitrate, and solvent molecules. All possible structures with the formula [AnIV(Cl)x(H2O)y(NO3)z]4-x-z (An=U, Np, and Pu; x=0-6, y=0-8, and z=0-6) were considered to explore the speciation chemical space of each actinide. The nature of the mixed-ligand complexes present in solution is controlled by the concentration of free ligands in solution. A low chloride concentration is suitable to drive the speciation away from the highly thermodynamically stable hexachloride species. Furthermore, the formation of dimeric species can proceed through both olation and oxolation mechanisms. Oxolation is preferred for monomers that contain fewer water ligands, while olation becomes favorable for the complexes with more water ligands.


Density Functional Theory

Supplementary materials

Supporting Information
Additional actinide speciation, olation, and oxolation energetics.


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