Uranium(IV) Incorporation into Inverse Spinel Magnetite (FeFe2O4): A Charge-Balanced Substitution Case Analysis

Abstract

Magnetite has gained significant attention owing to its good radionuclide solid solution and recovery capacity. In this paper, first-principle calculations are adopted to evaluate and analyse the formation energies, mechanical stabilities, bonding behaviours and magnetic properties of U(IV) ions incorporated into the magnetite lattice with different charge-balanced cases. The case indicated by B1, adding a U(IV) ion in an octahedron site and generating an octahedron Fe(III) ion vacancy, is most favourable for U(IV) incorporation into the magnetite lattice. Moreover, the corresponding models (named B1, C1 and D) for different amounts of U(IV) incorporation satisfy mechanical stability. The bond population and Mulliken charge population calculations show that the ionic bonding strength of Fe–O and UIV–O bonds is stronger in pure magnetite compared to the mentioned U(IV)-doped magnetite models. The spin-polarised density of states of U(IV)-doped magnetites are asymmetrical for the spin-up part and the spin-down part, indicating that the mentioned U(IV)-doped magnetites have good magnetic properties. Our work is expected to provide new ideas for the disposal of U(IV).