Uranium(IV) incorporation into inverse spinel magnetite ($\hbox {FeFe}_{2}\hbox {O}_{4}$): 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 $B_{1}$, 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 $B_{1}$, $C_{1}$ 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 $\hbox {U}^{\mathrm{IV}}$–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).