论文标题
量化核心分离近似的误差
Quantifying the error of the core-valence separation approximation
论文作者
论文摘要
为了计算通过X射线吸收光谱探测的核心兴奋状态，核心价分离（CVS）方案已成为至关重要的工具。这种方法允许以高特异性为目标，尽管引入了错误。我们报告了在极化传播器（ADC）的代数 - 二氧化述构建方案中获得的CVS激发的后处理步骤，该步骤消除了此错误。基于此，我们提供了对CVS方案的详细分析，确定其准确性是由两个被忽视的耦合之间的误差平衡所支配的，一个耦合之间的误差平衡是核心和价值单个激发之间的误差平衡，而单一核心和双核心激发之间的误差平衡。基集的选择证明对两个耦合的正确描述至关重要，并且对于良好的误差平衡所需的紧密极化功能是至关重要的。 CVS错误已被确认在多个系统上是稳定的，其特定于$ k $ - 边缘频谱计算的元素特定差异约为$ \ pm $ 0.02 ev。在考虑到极度扩散态的激发时，会注意到CVS误差的系统降低0.02-0.03 eV，从而模拟电离。
For the calculation of core-excited states probed through X-ray absorption spectroscopy, the core-valence separation (CVS) scheme has become a vital tool. This approach allows to target such states with high specificity, albeit introducing an error. We report the implementation of a post-processing step for CVS excitations obtained within the algebraic-diagrammatic construction scheme for the polarisation propagator (ADC), which removes this error. Based on this we provide a detailed analysis of the CVS scheme, identifying its accuracy to be dominated by an error balance between two neglected couplings, one between core and valence single excitations and one between single and double core excitations. The selection of the basis set is shown to be vital for a proper description of both couplings, with tight polarising functions being necessary for a good balance of errors. The CVS error is confirmed to be stable across multiple systems, with an element-specific spread for $K$-edge spectrum calculations of about $\pm$0.02 eV. A systematic lowering of the CVS error by 0.02-0.03 eV is noted when considering excitations to extremely diffuse states, emulating ionisation.
