Accurate first principles calculations for x-ray spectroscopy from polyanion-type cathode materials for lithium ion battery

过渡金属L2、3边x射线吸收近边结构（XANES）是实验观察阴极过渡金属离子在充放电循环过程中电子结构变化的有力技术。然而，一个可靠的基于量子力学的理论工具对于这些光谱的分析是必不可少的。在这项工作中，开发了新的L2,3边XANES的第一原理多电子方法，可以明确地处理大活动空间之间的电子相关性。然后，利用这些方法获得了聚阴离子型正极材料的过渡金属L2、3边XANES的理论指纹图谱，可用于实验结果的分析。

X-ray absorption near-edge structure (XANES) at L2,3-edges of transition metal is powerful technique to experimentally observe the change of electronic structure of transition metal ions in cathode during charge/discharge cycle. However, a reliable theoretical tool based on the quantum mechanics is indispensable for the analysis of these spectra. In this work, new first-principle many-electron approaches for L2,3-edge XANES, that can explicitly deal with the electronic correlations between large active space, are developed. Then, the theoretical fingerprints for transition metal L2,3-edge XANES of polyanion-type cathode materials that can be utilized for the analysis of experimental results are obtained by using these methods.