Importance of Counteranions on the Hydration Structure
of the Curium Ion
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Abstract
Using density functional theory based
ab initio molecular dynamics
and metadynamics, we show that counterions can trigger noticeable
changes in the hydration shell structure of the curium ion. On the
basis of the free energies of curium–water coordination, the
eight-fold coordination state is dominant by at least 98% in the absence
of counteranions and in the presence of chloride and bromide counteranions.
In addition, the solvent hydrogen bond (HB) lifetimes are relatively
longer. In contrast, the solvent hydrogen bond (HB) lifetimes are
relatively shorter in the presence of perchlorate counteranions, with
the nine-fold and eight-fold states existing in an 8/2 ratio, which
is in good agreement with the reported ratio measured by X-ray scattering
experiments. To our knowledge, this is the first time that molecular
simulations have shown that counteranions can directly affect the
first hydration shell structure of a cation