Finding Order in the Disordered Hydration Shell of Rapidly Exchanging Water Molecules around the Heaviest Alkali Cs + and Fr +

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Abstract

We report the structural and dynamical characterization of the intrinsically disordered hydration shells of the heaviest alkali ions, Cs + and Fr + , obtained in ab initio molecular dynamics simulations. The knowledge of solvation and complexation properties of short-lived Fr + is very limited and mostly based on extrapolations from the smaller alkali metal ions. To this end, we provide a critical insight into Fr + solvation, demonstrating an extreme example of disordered solvation with no distinction between the ion-bound and solvent-bound states of water based on the ion-water distance. However, these two states are distinguished through distance-solvent rearrangement correlation, where either coordination number or electric field is employed to treat solvent rearrangement. Utilizing reaction rate theory, we find that the water exchange time scale for Fr + (2.1-2.3 ps) is unexpectedly slower than for Cs + (0.5-1.2 ps), because Fr + experiences stronger nonequilibrium solvent effects. This study provides a new perspective on weak and hydrophobic solvation.

Original languageEnglish
Pages (from-to)12067-12076
Number of pages10
JournalJournal of Physical Chemistry B
Volume122
Issue number50
DOIs
StatePublished - Dec 20 2018

Funding

This research was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division and used resources of the Oak Ridge Leadership Computing Facility and the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which are supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. *E-mail: [email protected]. *E-mail: [email protected]. ORCID Santanu Roy: 0000-0001-6991-8205 Vyacheslav S. Bryantsev: 0000-0002-6501-6594 Notes The authors declare no competing financial interest. This manuscript has been authored [in part] by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/ downloads/doe-public-access-plan).

FundersFunder number
Data Environment for Science
US Department of Energy
UT-Battelle, LLCDE-AC05-00OR22725
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Cades Foundation

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