We present a general approach for the calculation and assignment of X-ray absorption spectra based on electronic wavepacket propagations performed using explicitly time-dependent electronic structure calculations. Such calculations have the appeal of yielding the entire absorption spectrum for the cost of a single set of electronic wavepacket propagations, obviating the need to explicitly calculate large numbers of core-excited states. The spectrum can either be calculated from the Fourier transform of the time-dependent dipole moment or from the Fourier transform of the wavepacket autocorrelation function. We propose that calculating the absorption spectrum using the latter approach will generally be the preferred option. This method has two important advantages. First, the autocorrelation functions can be obtained for twice the propagation time, resulting in a halving of the computational effort required to calculate the spectrum relative to the time-dependent dipole moment approach. Second, using the tools of filter diagonalisation, the autocorrelation functions may be used to determine the time-independent final core-excited states underlying the peaks of interest in the spectrum. The proposed scheme is validated by calculating and characterizing the X-ray absorption spectra of benzene and trifluoroacetonitrile at the time-dependent second-order algebraic diagrammatic construction level of theory.

中文翻译：

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计算和表征X射线吸收光谱的通用方法

我们提出了一种基于电子波包传播的X射线吸收光谱的计算和分配的通用方法，该过程使用明确的时间相关的电子结构计算来执行。这样的计算具有以单套电子波包传播为代价来产生整个吸收光谱的吸引力，从而无需明确计算大量的核激发态。频谱可以从与时间相关的偶极矩的傅立叶变换中得出，也可以从波包自相关函数的傅立叶变换中得出。我们建议使用后一种方法计算吸收光谱通常是首选方案。该方法具有两个重要优点。首先，可以获得两倍的传播时间的自相关函数，相对于与时间相关的偶极矩方法，可将计算频谱所需的计算量减少一半。其次，使用滤波器对角化的工具，自相关函数可用于确定在频谱中感兴趣的峰值之下的时间无关的最终核心激发态。通过在理论上依赖于时间的二阶代数图解构造水平上计算和表征苯和三氟乙腈的X射线吸收光谱，验证了该方案的有效性。自相关函数可用于确定与频谱相关的峰以下的时间无关的最终核激发态。通过在理论上依赖于时间的二阶代数图解构造水平上计算和表征苯和三氟乙腈的X射线吸收光谱，验证了该方案的有效性。自相关函数可用于确定与频谱相关的峰以下的时间无关的最终核激发态。通过在理论上依赖于时间的二阶代数图解构造水平上计算和表征苯和三氟乙腈的X射线吸收光谱，验证了该方案的有效性。