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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Simulating X-ray Absorption Spectra with Linear-Response Density Cumulant Theory
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Simulating X-ray Absorption Spectra with Linear-Response Density Cumulant Theory

机译：模拟具有线性响应密度累积累积理论的X射线吸收光谱

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摘要

We present a new approach for simulating X-ray absorption spectra based on linear-response density cumulant theory (LR-DCT) [Copan, A. V.; Sokolov, A. Yu. J. Chem. Theory Comput. 2018, 14, 4097-4108]. Our new method combines the LR-ODC-12 formulation of LR-DCT with core-valence separation approximation (CVS) that allows us to efficiently access high-energy core-excited states. We describe our computer implementation of the CVS-approximated LR-ODC-12 method (CVS-ODC-12) and benchmark its performance by comparing simulated X-ray absorption spectra to those obtained from experiment for several small molecules. Our results demonstrate that the CVS-ODC-12 method shows good agreement with experiment for relative spacings between transitions and their intensities, but the excitation energies are systematically overestimated. When compared to results from excited-state coupled cluster methods with single and double excitations, the CVS-ODC-12 method shows a similar performance for intensities and peak separations, while coupled cluster spectra are less shifted, relative to experiment. An important advantage of CVS-ODC-12 is that its excitation energies are computed by diagonalizing a Hermitian matrix, which enables efficient computation of transition intensities.
机译：我们提出了一种基于线性响应密度累积累积理论（LR-DCT）的X射线吸收光谱的新方法[Copan，A.V。; Sokolov，A. Yu。 J.Chem。理论计算。 2018,14,4097-4108]。我们的新方法将LR-ODC-12配方与LR-DCT的LR-ODC-12配方与核心价分离近似（CV）相结合，使我们能够有效地访问高能核心激发状态。我们通过将模拟的X射线吸收光谱与来自几个小分子的实验获得的那些进行比较来描述CVS近似的LR-ODC-12方法（CVS-ODC-12）的计算机实现，并通过将模拟的X射线吸收光谱进行比较来基准。我们的结果表明，CVS-ODC-12方法与转变与其强度之间的相对间距的实验表现出良好的一致性，但是激发能量被系统地高估。与具有单一和双激发的激发状态耦合群方法的结果相比，CVS-ODC-12方法显示了相似性的强度和峰值分离的性能，而耦合的聚类光谱相对于实验则较少移位。 CVS-ODC-12的一个重要优点是其激励能量通过对角度化密封矩阵来计算，这使得能够有效地计算转变强度。

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