发表机构
Brookhaven National Laboratory; University of Washington; Stony Brook University; National Institute of Standards and Technology（布鲁克海文国家实验室; 华盛顿大学; 石溪大学; 美国国家标准与技术研究院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究对九种钛化合物的Ti K边XANES模拟进行基准测试，发现四极激发、热无序和多体效应至关重要，并建立了高保真光谱数据库生成流程。
AI 中文摘要
X射线吸收光谱（XAS）是一种强大的、元素特异性的探针，用于研究材料的局域结构和电子性质。然而，定量分析仍然具有挑战性，需要精确的第一性原理光谱模拟。在本研究中，我们针对九种常见钛化合物，将Ti K边X射线吸收近边结构（XANES）的第一性原理模拟与实验数据进行了基准测试。我们系统地研究了关键物理效应，包括四极激发、热无序和多体振起效应。我们的结果表明，四极激发和热无序对于准确捕捉前边特征至关重要，而多体振起效应显著影响主边和后边区域的光谱形状。通过将这些效应与芯洞末态的能带理论处理相结合，我们的模拟光谱在大多数系统中与实验数据达到了极好的一致性，这由高相似度分数所证实。实验中BaTiO$_3$在4980 eV处的肩峰在模拟中基本缺失。进一步分析表明，需要比半局域密度泛函理论更精确的电子结构理论来捕捉Ba $4f$轨道的关联效应，并且缺陷（如氧空位）也可能对肩峰有所贡献。除了处理特定的钛材料体系外，这项工作为生成钛化合物的高保真Ti K边XANES数据库建立了稳健的工作流程，提供了一个可推广到广泛材料范围的框架。
英文摘要
X-ray absorption spectroscopy (XAS) is a powerful, element-specific probe for investigating the local structural and electronic properties of materials. However, quantitative analysis remains challenging, necessitating accurate first-principles spectral simulations. In this study, we benchmark first-principles simulations of Ti K-edge X-ray absorption near-edge structure (XANES) against experimental data for nine common titanium compounds. We systematically investigate key physical effects, including quadrupole excitations, thermal disorder, and many-body shake-up. Our results demonstrate that quadrupole excitations and thermal disorder are essential for capturing accurate pre-edge features, while many-body shake-up effects significantly influence the spectral shape of the main- and post-edge regions. By incorporating these effects alongside a band-theory treatment of the core-hole final state, our simulated spectra achieve excellent agreement with experimental data for most of the systems, as evidenced by high similarity scores. The shoulder peak in BaTiO$_3$ at 4980 eV in the experiment is largely missing in simulation. Further analysis shows that more accurate electronic structure theory than semi-local density functional theory is required to capture the correlation effects of the Ba $4f$ orbitals and that defects, such as oxygen vacancies, may also contribute to the shoulder. Beyond tackling specific titanium material systems, this work establishes a robust workflow for generating high-fidelity Ti K-edge XANES databases for titanium compounds, providing a framework that can be generalized to a broad range of materials.
