Structure and stability of aquotetrafluorouranyl(VI) in the solid state - Density functional study of [UO2F4(H2O)][NMe4]2·2H2O1,2

Abstract

Periodic density functional computations have been performed for solid [UO2F4(H2O)][NMe4]2·2H(2)O at the BLYP level. A model with disordered fluoro and aquo ligands in the uranyl anion is significantly lower in energy than one with a symmetrical assignment of these sites, which was favored in the original X-ray crystallography study. According to optimized energies and Car-Parrinello molecular dynamics (CPMD) simulations, the [UO2F4(H2O)]2- ion in the solid is stable with respect to loss of the coordinated water molecule. In contrast, CPMD simulations had found this ligand to be unbound in aqueous solution. The role of the counterions in stabilizing the higher coordination number in the crystal is discussed.