On the Structure of Aqueous Cesium Fluoride and Cesium Iodide Solutions: Diffraction Experiments, Molecular Dynamics Simulations, and Reverse Monte Carlo Modeling
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- 作者：Vikt贸ria Mile ; Orsolya Gereben ; Shinji Kohara ; L谩szl贸 Pusztai
- 刊名：The Journal of Physical Chemistry B
- 出版年：2012
- 出版时间：August 16, 2012
- 年：2012
- 卷：116
- 期：32
- 页码：9758-9767
- 全文大小：628K
- 年卷期：v.116,no.32(August 16, 2012)
- ISSN：1520-5207
文摘
A detailed study of the microscopic structure of two electrolyte solutions, cesium fluoride (CsF) and cesium iodide (CsI) in water, is presented. For revealing the influence of salt concentration on the structure, CsF solutions at concentrations of 15.1 and 32.3 mol % and CsI solutions at concentrations of 1.0 and 3.9 mol % are investigated. For each concentration, we combine total scattering structure factors from neutron and X-ray diffraction and 10 partial radial distribution functions from molecular dynamics simulations in one single structural model, generated by reverse Monte Carlo modeling. For the present solutions we show that the level of consistency between simulations that use simple pair potentials and experimental structure factors is at least semiquantitative for even the extremely highly concentrated CsF solutions. Remaining inconsistencies seem to be caused primarily by water鈥搘ater distribution functions, whereas slightly problematic parts appear on the ion鈥搊xygen partials, too. As a final result, we obtained particle configurations from reverse Monte Carlo modeling that were in quantitative agreement with both sets of diffraction data and most of the MD simulated partial radial distribution functions. From the particle coordinates, distributions of the number of first neighbors as well as angular correlation functions were calculated. The average number of water molecules around cations in both materials decreases from about 8.0 to about 5.1 as concentration increases, whereas the same quantity for the anions (X) changes from about 5.3 to about 3.7 in the case of CsF and from about 6.2 to about 4.0 in the case of CsI. The average angle of X路路路H鈥揙 particle arrangements, characteristic of anion鈥搘ater hydrogen bonds, is closer to 180掳 than that found for O路路路H鈥揙 arrangements (water鈥搘ater hydrogen bonds) at higher concentrations.