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Title: Unraveling halide hydration: A high dilution approach

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 halidemore » 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.« less
Authors:
; ;  [1] ;  [2]
  1. Dipartimento di Chimica, Università di Roma “La Sapienza”, P. le A. Moro 5, 00185 Roma (Italy)
  2. Sincrotrone Trieste S.C.p.A s.s. 14, km 163.5, I-34149 Basovizza, Trieste (Italy)
Publication Date:
OSTI Identifier:
22419950
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; ABSORPTION SPECTROSCOPY; AQUEOUS SOLUTIONS; COMPARATIVE EVALUATIONS; DILUTION; FINE STRUCTURE; FREE ENERGY; HALIDES; HYDRATION; INTERACTIONS; MOLECULAR DYNAMICS METHOD; PERTURBATION THEORY; PROTONS; X RADIATION; X-RAY SPECTROSCOPY