典型温稠密物质X射线吸收谱的理论模拟研究

Studies of warm dense mater (WDM) have shown remarkable importance in various fields of physics, including astrophysics and inertial confinement fusion (ICF). X-ray absorption spectrum (XAS) is a powerful tool for the detection of microscopic properties and macroscopic conditions of WDM. Theoretical simulations of XAS can help to directly relate the structures and properties of the materials to the shape and position of XAS curves. Furthermore, this kind of studies can provide useful data and physical explanations for experimental XAS results. Traditional first-principles XAS simulation methods based on the one-electron approximation and the frozen-core approximation are not accurate enough, especially for WDM. In this project, we will modify the traditional method, making it more capable for the description of WDM. We will also develop a new simulation method based on many-body theory, which can better describe the electron excitation process. Our methods will apply to a series of ICF related materials under warm dense conditions, including metals of beryllium, gold and uranium, as well as organic polymer materials, and the influence of external conditions and atomic structures on the XAS curves is discussed. These results will provide useful information for future XAS measurements and ICF experiments.

温稠密物质的研究在天体物理和惯性约束聚变等领域具有重要意义。X射线吸收谱是探测温稠密物质微观性质和宏观状态的有效手段。在理论上模拟X射线吸收谱可以直接建立物质的结构、物性与吸收谱形状、位置的关联，并进一步为实验上吸收谱的测量结果提供数据支持和理论解释。传统的基于单电子近似和冻芯近似的X射线吸收谱理论模拟方法在模拟温稠密物质时不够准确。本项目中我们将改进传统的模拟方法，使其更适合描述温稠密物质。我们还将发展新的基于多体理论的方法，从而可以更好地描述电子激发过程。我们的方法将应用于研究一系列惯性约束聚变相关材料，包括金属材料铍、金和铀以及有机聚合物材料，在温稠密状态下的X射线吸收谱，以及各种外部条件和原子结构对X射线吸收谱的影响。我们的结果将为吸收谱测量以及惯性约束聚变相关实验提供有用的信息。

温稠密物质的研究在天体物理和惯性约束聚变等领域具有重要意义,而X射线吸收谱是探测温稠密物质微观性质和宏观状态的有效手段。在本项目中，我们发展了基于单电子近似的方法和基于含时密度泛函的方法来模拟X射线吸收谱，并系统获得了金属铝、甲烷、氨等材料在温稠密状态下的吸收谱，分析了影响吸收谱的各种因素。计算发现，对于金属的吸收谱，其吸收边形状主要由Fermi-Dirac分布主导，对体系温度较为敏感；对于小分子的吸收谱，化学键的断裂以及新结构的形成会导致吸收谱有显著的变化。我们的结果将为吸收谱测量以及温稠密物质相关实验提供有用的信息。