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首页> 外文期刊>Physica Scripta: An International Journal for Experimental and Theoretical Physics >Atomistic simulations of the Fe K-edge EXAFS in FeF3 using molecular dynamics and reverse Monte Carlo methods
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Atomistic simulations of the Fe K-edge EXAFS in FeF3 using molecular dynamics and reverse Monte Carlo methods

机译：使用分子动力学和反向蒙特卡洛方法对FeF3中的Fe K-edge EXAFS进行原子模拟

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摘要

Atomistic simulations of the experimental Fe K-edge extended x-ray absorption fine structure (EXAFS) of rhombohedral (space groupR (3) over barc) FeF3 at T = 300. K were performed using classical molecular dynamics and reverse Monte Carlo (RMC) methods. The use of two complementary theoretical approaches allowed us to account accurately for thermal disorder effects in EXAFS and to validate the developed force-field model, which was constructed as a sum of two-body Buckingham-type (Fe-F and F-F), three-body harmonic (Fe-F-Fe) and Coulomb potentials. We found that the shape of the Fe K-edge EXAFS spectrum of FeF3 is a more sensitive probe for the determination of potential parameters than the values of structural parameters (a, c, x(F)) available from diffraction studies. The best overall agreement between the experimental and theoretical EXAFS spectra calculated using ab initio multiple-scattering approach was obtained for the iron effective charge q(Fe) = 1.71. The RMC method coupled with the evolutionary algorithm was used for more elaborate analysis of the EXAFS data. The obtained results suggest that our force-field model slightly underestimates the amplitude of thermal vibrations of fluorine atoms in the direction perpendicular to the Fe-F bonds.
机译：T = 300时菱形（空间基体R（3）在barc上）FeF3的实验Fe K边缘扩展x射线吸收精细结构（EXAFS）的原子模拟。K是使用经典分子动力学和反向蒙特卡洛（RMC）进行的方法。两种互补理论方法的使用使我们能够准确地解释EXAFS中的热失调效应，并验证所开发的力场模型，该模型由两体白金汉型（Fe-F和FF），三体谐波（Fe-F-Fe）和库仑电势。我们发现，FeF3的Fe K-edge EXAFS光谱的形状比潜在的衍射研究结构参数（a，c，x（F））的值对确定潜在参数更敏感。对于铁有效电荷q（Fe）= 1.71，使用从头算多次散射方法计算得出的实验和理论EXAFS光谱之间的最佳总体一致性最佳。 RMC方法与进化算法相结合，用于对EXAFS数据进行更精细的分析。所得结果表明，我们的力场模型略微低估了氟原子在垂直于Fe-F键的方向上的热振动幅度。

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