Unraveling halide hydration: A high dilution approach
- Dipartimento di Chimica, Università di Roma “La Sapienza”, P. le A. Moro 5, 00185 Roma (Italy)
- Sincrotrone Trieste S.C.p.A s.s. 14, km 163.5, I-34149 Basovizza, Trieste (Italy)
The hydration properties of halide aqua ions have been investigated combining classical Molecular Dynamics (MD) with Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Three halide-water interaction potentials recently developed [M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144104 (2011)], along with three plausible choices for the value of the absolute hydration free energy of the proton (ΔG{sub hyd}{sup ⊖}[H{sup +}]), have been checked for their capability to properly describe the structural properties of halide aqueous solutions, by comparing the MD structural results with EXAFS experimental data. A very good agreement between theory and experiment has been obtained with one parameter set, namely L{sub E}, thus strengthening preliminary evidences for a ΔG{sub hyd}{sup ⊖}[H{sup +}] value of −1100 kJ mol{sup −1} [M. M. Reif and P. H. Hünenberger, J. Chem. Phys. 134, 144104 (2011)]. The Cl{sup −}, Br{sup −}, and I{sup −} ions have been found to form an unstructured and disordered first hydration shell in aqueous solution, with a broad distribution of instantaneous coordination numbers. Conversely, the F{sup −} ion shows more ordered and defined first solvation shell, with only two statistically relevant coordination geometries (six and sevenfold complexes). Our thorough investigation on the effect of halide ions on the microscopic structure of water highlights that the perturbation induced by the Cl{sup −}, Br{sup −}, and I{sup −} ions does not extend beyond the ion first hydration shell, and the structure of water in the F{sup −} second shell is also substantially unaffected by the ion.
- OSTI ID:
- 22419950
- Journal Information:
- Journal of Chemical Physics, Vol. 141, Issue 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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