Abstract
From density functional theory (DFT) based ab initio (Car-Parrinello) metadynamics, we compute the activation energies and mechanisms of water exchange between the first and second hydration shells of aqueous Uranyl (UO22+) using the primary hydration number of U as the reaction coordinate. The free energy and activation barrier of the water dissociation reaction [UO2(OH2)5]2+(aq) → [UO2(OH2)4]2+(aq) + H2O are 0.7 kcal and 4.7 kcal/mol respectively. The free energy is in good agreement with previous theoretical (-2.7 to +1.2 kcal/mol) and experimental (0.5 to 2.2 kcal/mol) data. The associative reaction [UO2(OH2)5]2+(aq) + H2O → [UO2(OH2)6]2+(aq) is short-lived with a free energy and activation barrier of +7.9 kcal/mol and +8.9 kca/mol respectively; it is therefore classified as associative-interchange. On the basis of the free energy differences and activation barriers, we predict that the dominant exchange mechanism between [UO2(OH2)5]2+(aq) and bulk water is dissociative.
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References
Richens D. T. The Chemistry of Aqua Ions. Chichester: John Wiley & Sons, 1997.
Helm L.; Merbach A. E. Chem. Rev. 2005, 105, 1923.
Nichols P.; Bylaska E. J.; Schenter G. K.; de Jong W. A. J. Chem. Phys. 2008, 128, 124507.
Neuefeind J.; Soderholm L.; Skanthakumar S. J. Phys. Chem. A 2004, 109, 2733.
Soderholm L.; Skanthakumar S.; Neuefeind J. Anal. Bioanal. Chem. 2005, 383, 48.
K. E. Gutowski, K. E Dixon, D. A. J. Phys. Chem. A 2008, 110, 8840.
Spencer S. et al. J. Phys. Chem. A 1999, 103, 1831.
Hay P. J. J. Chem. Phys. 1983, 79, 5469.
Vallet V.; Privalov T.; Wahlgren U.; Grenthe I. J. Am. Chem. Soc. 2004, 126, 7766.
Bühl M.; Diss R.; Wipff G. J. Am. Chem. Soc. 2005, 127, 13506.
Bühl M.; Kabreden H. Inorg. Chem. 2006, 45, 3834.
Farkas I.; Bányai I.; Szabó Z.; Wahlgren U.; Grenthe I. Inorg. Chem. 2000, 39, 799.
Laio A.; Parrinello M. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 12562.
Laio A.; Gervasio F. L. Rep. Prog. Phys. 2008, 71, 126601.
Barducci A.; Bussi G.; Parrinello M. Phys. Rev. Lett. 2008, 100, 020603
Car R.; Parrinello M.. Phys. Rev. Lett. 1985, 55, 2471.
Kohn W.; Sham L. J. Phys. Rev. 1965, 140, A1133.
Valiev M. et al. Comput. Phys. Commun. 2010, 181, 1477.
Perdew J. P.; Burke K.; Ernzerhof M. Phys. Rev. Lett. 1996, 77, 3865.
Kleinman L.; Bylander D. M. Phys. Rev. Lett. 1982, 48, 1425.
Nose S. Mol. Phys. 1984, 52, 255; Hoover, W. G. Phys. Rev. A, 1985, 31, 1695.
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Atta-Fynn, R., Bylaska, E.J. & de Jong, W.A. Free energies and mechanisms of water exchange around Uranyl from first principles molecular dynamics. MRS Online Proceedings Library 1383, 113–118 (2011). https://doi.org/10.1557/opl.2012.181
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DOI: https://doi.org/10.1557/opl.2012.181