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首页> 外文会议>International Conference of Computational Methods in Sciences and Engineering 2007(ICCMSE 2007); 20070925-30; Corfu(GR) >Coupling MD Simulations and X-ray Absorption Spectroscopy to Study Ions in Solution
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Coupling MD Simulations and X-ray Absorption Spectroscopy to Study Ions in Solution

机译：耦合MD模拟和X射线吸收光谱研究溶液中的离子

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摘要

The structure of ionic solutions is a key-point in understanding physicochemical properties of electrolyte solutions. Among the reduced number of experimental techniques which can supply direct information on the ion environment, X-ray Absorption techniques (XAS) have gained importance during the last decades although they are not free of difficulties associated to the data analysis leading to provide reliable structures. Computer simulations of ions in solution is a theoretical alternative to provide information on the solvation structure. Thus, the use of computational chemistry can increase the understanding of these systems although an accurate description of ionic solvation phenomena represents nowadays a significant challenge to theoretical chemistry. We present: (a) the assignment of features in the XANES spectrum to well defined structural motif in the ion environment, (b) MD-based evaluation of EXAFS parameters used in the fitting procedure to make easier the structural resolution, and (c) the use of the agreement between experimental and simulated XANES spectra to help in the choice of a given intermolecular potential for Computer Simulations. Chemical problems examined are: (a) the identification of the second hydration shell in dilute aqueous solutions of highly-charged cations, such as Cr~(3+), Rh~(3+), Ir~(3+), (b) the invisibility by XAS of certain structures characterized by Computer Simulations but exhibiting high dynamical behavior and (c) the solvation of Br~- in acetonitrile.
机译：离子溶液的结构是理解电解质溶液理化性质的关键。在减少的能够提供有关离子环境的直接信息的实验技术中，X射线吸收技术（XAS）在过去的几十年中变得越来越重要，尽管它们没有摆脱与提供可靠结构的数据分析相关的困难。溶液中离子的计算机模拟是提供有关溶剂化结构信息的理论选择。因此，尽管如今对离子溶剂化现象的准确描述对理论化学构成了重大挑战，但使用计算化学可以增进对这些系统的了解。我们提出：（a）XANES光谱中的特征分配给离子环境中定义明确的结构基序；（b）基于MD的EXAFS参数评估，用于拟合过程，以简化结构分辨率；以及（c）利用实验XANES和模拟XANES光谱之间的一致性来帮助选择给定的计算机模拟分子间潜力。所检查的化学问题是：（a）在高电荷阳离子如Cr〜（3 +），Rh〜（3 +），Ir〜（3+）等稀水溶液中鉴定第二个水合壳（b ）XAS对某些以计算机模拟为特征但显示出高动力学行为的结构的不可见性；以及（c）Br〜-在乙腈中的溶剂化。

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