Calculating X-ray Absorption Spectra of Open-Shell Molecules with the Unrestricted Algebraic-Diagrammatic Construction Scheme for the Polarization Propagator.
Calculating X-ray Absorption Spectra of Open-Shell Molecules with the Unrestricted Algebraic-Diagrammatic Construction Scheme for the Polarization Propagator.
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DOI：
10.1021/ct5006888
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发表时间：
2014-09
影响因子：
5.5
通讯作者：
J. Wenzel;M. Wormit;A. Dreuw
中科院分区：
文献类型：
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作者：
J. Wenzel;M. Wormit;A. Dreuw
X射线吸收光谱（XAS）是一种强大的工具，通过激发电子从K壳层核心区域到未占据的分子水平，提供有关分子电子结构的信息。这些高激发态的电子芯激发态可以通过将芯-价分离（CVS）近似应用于ADC（2）工作方程，使用二阶ADC（2）的代数图解构造方案来精确计算。首次提出了一种有效的非限制性CVS-ADC（2）变体CVS-UADC（2）的实现方法，通过将α和β自旋彼此分开处理来计算开壳层分子。通过与标准TD-DFT/B3 LYP值和实验数据的比较，用一组小的有机自由基证明了CVS-UADC（2）方法的潜力。事实证明，特别是扩展变体CVS-UADC（2）-x提供了最准确的结果，与实验值相比误差仅为0.1%。这种显著的一致性证明了尚未记录的实验XAS光谱的预测，如蒽阳离子的预测。由于半满单占据分子轨道，阳离子表现出额外的峰，这可能有助于区分阳离子和中性物质。
X-ray absorption spectroscopy (XAS) is a powerful tool that provides information about the electronic structure of molecules via excitation of electrons from the K-shell core region to the unoccupied molecular levels. These high-lying electronic core-excited states can be accurately calculated using the algebraic-diagrammatic construction scheme of second order ADC(2) by applying the core-valence separation (CVS) approximation to the ADC(2) working equations. For the first time, an efficient implementation of an unrestricted CVS-ADC(2) variant CVS-UADC(2) is presented for the calculation of open-shell molecules by treating α and β spins separately from each other. The potential of the CVS-UADC(2) method is demonstrated with a set of small organic radicals by comparison with standard TD-DFT/B3LYP values and experimental data. It turns out that the extended variant CVS-UADC(2)-x, in particular, provides the most accurate results with errors of only 0.1% compared to experimental values. This remarkable agreement justifies the prediction of yet nonrecorded experimental XAS spectra like the one of the anthracene cation. The cation exhibits additional peaks due to the half-filled single-occupied molecular orbital, which may help to distinguish cation from the neutral species.