Hydration Structure of No: A Density Functional Theory-Molecular Dynamics Study.

The hydration structure of No, the divalent cation of nobelium in water, was investigated by ab initio molecular dynamics (MD) simulations. First, a series of benchmark calculations were performed to validate the density functional theory (DFT) calculation methods for a molecule containing a No atom. The DFT-MD simulation of the hydration structure of No was conducted after the MD method was validated by simulating the hydration structures of Ca and Sr, whose behavior was previously reported to be similar to that of No. The model cluster containing M (M = Ca, Sr, or No) and 32 water molecules was used for DFT-MD simulation. The results showed that the hydration distance of No was intermediate between those of Ca and Sr. This trend in the hydration distance is in good agreement with the elution position trend obtained in a previous radiochemical experiment. The calculated No-O bond lengths in the optimized structure of [No(HO)] was 2.59 Å, while the average No-O bond length of [No(HO)] in water by DFT-MD was 2.55 Å. This difference implies the importance of dynamic solvent effects, considering the second (and further) coordination sphere in the theoretical calculation of solution chemistry for superheavy elements.