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首页> 外文期刊>The Journal of Chemical Physics >AN EXTENDED X-RAY ABSORPTION FINE STRUCTURE STUDY BY EMPLOYING MOLECULAR DYNAMICS SIMULATIONS - BROMIDE ION IN METHANOLIC SOLUTION
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AN EXTENDED X-RAY ABSORPTION FINE STRUCTURE STUDY BY EMPLOYING MOLECULAR DYNAMICS SIMULATIONS - BROMIDE ION IN METHANOLIC SOLUTION

机译：应用分子动力学模拟扩展的X射线吸收精细结构-甲醇溶液中的溴离子。

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X-ray absorption spectroscopy is widely employed in the structural analysis of disordered systems. In the standard extended x-ray absorption fine structure (EXAFS) analysis the coordination of the photoabsorber is usually defined by means of Gaussian shells. It is known that this procedure can lead to significant errors in the determination of the coordination parameters for systems which present anharmonic thermal vibrations or interatomic asymmetric pair distribution functions. An efficient method has been recently employed in the study of the hydration shells of bromide and rubidium ions and brominated hydrocarbon molecules in diluted aqueous solutions. According to this method, pair distribution functions [g(r)] obtained from molecular dynamics simulations can be used as relevant models in the calculation of the EXAFS signals. Moreover, asymmetric shells modeled on the g(r) first peaks, have been employed in the EXAFS analysis and the parameters defining the asymmetric peaks have been optimized during the minimization procedure. In the present paper this new procedure has been used to investigate the coordination of Br- in methanol. The analysis of this system is particularly interesting due to the presence of three well separated coordination shells. We show that the inclusion of the hydrogen signal is essential to perform a reliable analysis. A comparison of the analysis with asymmetric and Gaussian shells shows how the accuracy of the EXAFS data analysis is improved by using asymmetric shells. (C) 1996 American Institute of Physics. [References: 59]
机译：X射线吸收光谱法广泛用于无序系统的结构分析中。在标准的扩展X射线吸收精细结构（EXAFS）分析中，通常通过高斯壳来定义光吸收剂的配位。众所周知，对于存在非谐热振动或原子间不对称对分布函数的系统，此过程可能会导致确定协调参数时出现重大错误。最近，在研究稀释水溶液中的溴化物，id离子和溴化烃分子的水合壳时，采用了一种有效的方法。根据这种方法，从分子动力学模拟获得的对分布函数[g（r）]可以用作EXAFS信号计算中的相关模型。此外，在EXAFS分析中采用了以g（r）第一峰为模型的不对称壳，并且在最小化过程中优化了定义不对称峰的参数。在本文中，该新方法已用于研究Br-在甲醇中的配位。由于存在三个分隔良好的协调壳，因此对该系统的分析特别有趣。我们表明，包含氢信号对于执行可靠的分析至关重要。通过对不对称壳和高斯壳的分析的比较，可以看出使用不对称壳如何提高EXAFS数据分析的准确性。 （C）1996年美国物理研究所。 [参考：59]

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