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The Aqueous Ca2+ System, in Comparison with Zn2+, Fe3 +, and Al3 +: An Ab Initio Molecular Dynamics Study

Authors

  • Dr. Stuart Bogatko,

    Corresponding author
    1. Chemistry and Biochemistry Department, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (USA)
    2. Current address: Eenheid Algemene Chemie, Vrije Universiteit Brussel (VUB), Faculteit Wetenschappen, Pleinlaan 2, 1050 Brussels (Belgium)
    • Chemistry and Biochemistry Department, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (USA)
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  • Dr. Emilie Cauët,

    1. Chemistry and Biochemistry Department, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (USA)
    2. Current address: Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles, CP 160/09, 50 Avenue F. D. Roosevelt, 1050 Brussels (Belgium)
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  • Dr. Eric Bylaska,

    1. Pacific Northwest National Laboratory, Richland, WA (USA)
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  • Dr. Gregory Schenter,

    1. Pacific Northwest National Laboratory, Richland, WA (USA)
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  • Dr. John Fulton,

    1. Pacific Northwest National Laboratory, Richland, WA (USA)
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  • Prof. John Weare

    1. Chemistry and Biochemistry Department, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (USA)
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Abstract

Herein, we report on the structure and dynamics of the aqueous Ca2+ system studied by using ab initio molecular dynamics (AIMD) simulations. Our detailed study revealed the formation of well-formed hydration shells with characteristics that were significantly different to those of bulk water. To facilitate a robust comparison with state-of-the-art X-ray absorption fine structure (XAFS) data, we employ a 1st principles MD-XAFS procedure and directly compare simulated and experimental XAFS spectra. A comparison of the data for the aqueous Ca2+ system with those of the recently reported Zn2+, Fe3+, and Al3+ species showed that many of their structural characteristics correlated well with charge density on the cation. Some very important exceptions were found, which indicated a strong sensitivity of the solvent structure towards the cation′s valence electronic structure. Average dipole moments for the 2nd shell of all cations were suppressed relative to bulk water.

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