W L $_3$边扩展X射线吸收精细结构的局部结构重建与理论验证
Advanced approach to the local structure reconstruction and theory validation on the example of the W L$_3$-edge extended X-ray absorption fine structure of tungsten
摘要：
采用经典分子动力学（MD）和反向蒙特卡罗（RMC）方法，对体心立方钨在T = 300 K时的W L $_3$边扩展X射线吸收精细结构（EXAFS）进行了原子模拟.基于MD模拟结果的MD-EXAFS方法使我们能够访问EXAFS中编码的结构信息，超出第一配位壳层，并验证两种相互作用势模型的准确性-嵌入原子模型势和第二近邻修正嵌入原子方法势。的RMC-EXAFS方法被用于更详细的EXAFS数据的分析，获得热无序效应。这两种方法的结果表明，体心立方钨中原子运动的相关性在8 Ω以上变得可以忽略不计。这一事实使我们能够使用EXAFS数据来确定不仅原子W-W对运动的均方相对位移，而且单个钨原子的均方位移，这通常只能从衍射数据中获得。
英文摘要：
Atomistic simulations of the experimental W L$_3$-edge extended X-ray absorption fine structure (EXAFS) of bcc tungsten at T = 300 K were performed using classical molecular dynamics (MD) and reverse Monte Carlo (RMC) methods. The MD-EXAFS method based on the results of MD simulations allowed us to access the structural information, encoded in EXAFS, beyond the first coordination shell and to validate the accuracy of two interaction potential models - the embedded atom model potential and the second nearest-neighbor modified embedded atom method potential. The RMC-EXAFS method was used for more elaborate analysis of the EXAFS data giving access to thermal disorder effects. The results of both methods suggest that the correlation in atomic motion in bcc tungsten becomes negligible above 8 Å. This fact allowed us to use the EXAFS data to determine not only mean-square relative displacements of atomic W-W pair motion but also mean-square displacements of individual tungsten atoms, which are usually accessible from diffraction data only.
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