基于修正Chihara公式的DFT-MD模拟X射线汤姆逊散射谱研究
X-ray Thomson scattering spectra from DFT-MD simulations based on a modified Chihara formula
AI总结：
本文提出基于修正Chihara公式和DFT-MD模拟计算X射线汤姆逊散射谱的方法，比较Mermin介电函数与LR-TDDFT框架，发现前者在环境密度铍中表现优异但在高度压缩物质中失效，并利用LR-TDDFT重新分析实验证明传统模型在小散射角下存在显著偏差。
摘要：
我们研究了基于修正Chihara公式从密度泛函理论分子动力学（DFT-MD）模拟计算X射线汤姆逊散射谱的最先进方法，该公式将非弹性贡献用介电函数表示。我们比较了使用从头算电子-离子碰撞频率从Mermin介电函数计算的电子动态结构因子，与使用线性响应含时密度泛函理论（LR-TDDFT）框架对氢和铍的计算结果，并研究了自由-自由和束缚-自由贡献对散射信号的色散。在Mermin介电函数中分别处理这些贡献，对于环境密度铍与LR-TDDFT结果高度一致，但对于束缚态被压力电离的高度压缩物质则失效。使用LR-TDDFT重新分析了铍的X射线汤姆逊散射实验，证明在小散射角下与传统解析模型推断的等离子体条件存在显著偏差。
英文摘要：
We study state-of-the-art approaches for calculating x-ray Thomson scattering spectra from density functional theory molecular dynamics (DFT-MD) simulations based on a modified Chihara formula that expresses the inelastic contribution in terms of the dielectric function. We compare the electronic dynamic structure factor computed from the Mermin dielectric function using an ab initio electron-ion collision frequency to computations using a linear response time dependent density functional theory (LR-TDDFT) framework for hydrogen and beryllium and investigate the dispersion of free-free and bound-free contributions to the scattering signal. A separate treatment of these contributions in the Mermin dielectric function shows excellent agreement with LR-TDDFT results for ambient-density beryllium, but breaks down for highly compressed matter where the bound states become pressure ionized. LR-TDDFT is used to reanalyze x-ray Thomson scattering experiments on beryllium demonstrating strong deviations from the plasma conditions inferred with traditional analytic models at small scattering angles.
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