Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Hydration of uranyl(VI) ion has been a subject of both theoretical and experimental interests for many years. Most of recent publications from both theory and experimental sides agree that the uranyl(VI) ion in aqueous solution exists as 5-fold UO2(H2O)52+. In this work, we studied the hydration of uranyl(VI, V) and neptunyl(VI) ions in further accurate way by optimizing structures of AnO2(H2O)n2+/+ (n = 4, 5, 6) clusters at the DFT level in aqueous solution using polarizable continuum model (PCM); with special focus on the conformation of coordinating water molecules. A stable energy minimum with no imaginary vibrational frequency was found for UO2(H2O)52+ having U-Oax distance of 1.756 and 1.757Å, and U-Oeq distance of 2.428, 2.436, 2.441, 2.441, and 2.443Å. Three water planes stay perpendicular to the equatorial plane, while two water planes stay parallel to the equatorial plane. Structures and energies of 4-, and 5-fold uranyl(VI,V) and neptunyl(VI) hydrates were studied and compared with recent experimental data some of which suggest presence of 4-fold actinyl hydrates.