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Title: Rate theory on water exchange in aqueous uranyl ion

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USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Chemical Physics Letters
Additional Journal Information:
Journal Volume: 671; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-12-06 04:24:46; Journal ID: ISSN 0009-2614
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Citation Formats

Dang, Liem X., Vo, Quynh N., Nilsson, Mikael, and Nguyen, Hung D. Rate theory on water exchange in aqueous uranyl ion. Netherlands: N. p., 2017. Web. doi:10.1016/j.cplett.2017.01.020.
Dang, Liem X., Vo, Quynh N., Nilsson, Mikael, & Nguyen, Hung D. Rate theory on water exchange in aqueous uranyl ion. Netherlands. doi:10.1016/j.cplett.2017.01.020.
Dang, Liem X., Vo, Quynh N., Nilsson, Mikael, and Nguyen, Hung D. Wed . "Rate theory on water exchange in aqueous uranyl ion". Netherlands. doi:10.1016/j.cplett.2017.01.020.
title = {Rate theory on water exchange in aqueous uranyl ion},
author = {Dang, Liem X. and Vo, Quynh N. and Nilsson, Mikael and Nguyen, Hung D.},
abstractNote = {},
doi = {10.1016/j.cplett.2017.01.020},
journal = {Chemical Physics Letters},
number = C,
volume = 671,
place = {Netherlands},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.cplett.2017.01.020

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Cited by: 1work
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  • We report one of the first simulations using a classical rate theory approach to predict the mechanism of the exchange process between water and aqueous uranyl ions. Using our water and ion-water polarizable force fields and molecular dynamics techniques, we computed the potentials of mean force for the uranyl ion-water pair as the function of pressures at ambient temperature. Subsequently, these simulated potentials of mean force were used to calculate rate constants using the transition rate theory; the time dependent transmission coefficients were also examined using the reactive flux method and Grote-Hynes treatments of the dynamic response of the solvent.more » The computed activation volumes using transition rate theory and the corrected rate constants are positive, thus the mechanism of this particular water-exchange is a dissociative process. We discuss our rate theory results and compare them with previously studies in which non-polarizable force fields were used. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The calculations were carried out using computer resources provided by the Office of Basic Energy Sciences.« less
  • The structures and vibrational frequencies of UO₂(H₂O)₄ ²⁺ and UO₂(H₂O)₅ ²⁺ have been calculated using density functional theory and are in reasonable agreement with experiment. The energies of various reactions were calculated at the density functional theory (DFT) and MP2 levels; the latter provides the best results. Self-consistent reaction field calculations in the PCM and SCIPCM approximations predicted the free energy of the water exchange reaction, UO₂(H₂O)₄ ²⁺ + H₂O T UO₂(H₂O)₅ ²⁺. The calculated free energies of reaction are very sensitive to the choice of radii (O and H) and isodensity values in the PCM and SCIPCM models, respectively.more » Results consistent with the experimental HEXS value of -1.19 plus or minus 0.42 kcal/mol (within 1-3 kcal/mol) are obtained with small cavities. The structures and vibrational frequencies of the clusters with second solvation shell waters: UO₂2(H₂2O)₄(H₂2O)₈ ²⁺, UO₂(H₂O)₄(H₂O)sub10 ²⁺, UO₂(H₂O)₄(H₂O)sub11 ²⁺, UO₂(H₂O)₅- (H₂O)₇ ²⁺, and UO₂(H₂O)5(H₂O)sub10 ²⁺, were calculated and are in better agreement with experiment as compared to reactions involving only UO₂(H₂O)₄ ²⁺ and UO₂(H₂O)₅ ²⁺. The MP2 reaction energies for water exchange gave gas-phase results that agreed with experiment in the range -5.5 to +3.3 kcal/mol. The results were improved by inclusion of a standard PCM model with differences of -1.2 to +2.7 kcal/mol. Rearrangement reactions based on an intramolecular isomerization leading to a redistribution of water in the two shells provide good values in comparison to experiment with values of ΔGexchange from -2.2 to -0.5 kcal/mol so the inclusion of a second hydration sphere accounts for most solvation effects. Calculation of the free energy of solvation of the uranyl cation yielded an upper bound to the solvation energy of -410 plus or minus 5 kcal/mol, consistent with the best experimental value of -421 plus or minus 15 kcal/mol.« less