标题： 从用于温暖稠密氢的从头算路径积分蒙特卡罗模拟中估算电离状态和连续谱降低 显示英文标题

标题： Estimating ionization states and continuum lowering from ab initio path integral Monte Carlo simulations for warm dense hydrogen

摘要： 热密物质（WDM）是一个活跃的研究领域，其应用范围从天体物理学到惯性约束聚变。电离度和连续谱降低是理解材料在这些条件下行为的重要量，但由于实验活动有限且通常需要依赖模型的分析，因此难以诊断。这对于氢气尤其如此，因为其散射截面相对较低，使得获得高质量数据尤为困难。因此，构建状态方程表通常依赖于精确模拟，并结合未经验证的近似方法从实验中提取特性。在此，我们研究了一种方法，利用化学模型从精确的第一性原理路径积分蒙特卡罗（PIMC）模拟中提取电离势降低和电离度——这些量通常无法直接从物理模型中获得。与实验测量不同，实验中噪声和非平衡效应会增加推断参数的不确定性，而PIMC模拟提供了清晰的信号和定义明确的热力学条件。与常用模型的比较显示有定性一致，但我们发现主要在高密度和高温情况下存在偏差。我们还展示了在X射线汤姆逊散射实验中，随着散射角的增加，动态结构因子对电离和连续谱降低的敏感性下降。我们的工作对未来实验的设计具有重要意义，同时也提供了对从精确量子蒙特卡罗模拟中获得的结构因子和虚时关联函数的定性理解。 显示英文摘要

摘要： Warm dense matter (WDM) is an active field of research, with applications ranging from astrophysics to inertial confinement fusion. Ionization degree and continuum lowering are important quantities to understand how materials behave under these conditions, but can be difficult to diagnose since experimental campaigns are limited and often require model-dependent analysis. This is especially true for hydrogen, which has a comparably low scattering cross section, making high quality data particularly difficult to obtain. Consequently, building equation of state tables often relies on exact simulations in combination with untested approximations to extract properties from experiments. Here, we investigate an approach for extracting the ionization potential depression and ionization degree -- quantities which are otherwise not directly accessible from the physical model -- from exact ab initio path integral Monte Carlo (PIMC) simulations utilizing a chemical model. In contrast to experimental measurements, where noise and non-equilibrium effects add to the uncertainty of the inferred parameters, PIMC simulations provide a clean signal with well-defined thermodynamic conditions. Comparisons against commonly used models show a qualitative agreement, but we find deviations primarily for the high density and high temperature cases. We also demonstrate the decreasing sensitivity of the dynamic structure factor with respect to both ionization and continuum lowering for increasing scattering angles in x-ray Thomson scattering experiments. Our work has important implications for the design of future experiments, but also offers qualitative understanding of structure factors and the imaginary-time correlation function obtained from exact quantum Monte Carlo simulations.