论文标题
Nexaf和XPS具有近似三重激发的EOM-CC方法
EOM-CC Methods with Approximate Triple Excitations for NEXAFS and XPS
论文作者
论文摘要
在计算K-边缘核心兴奋和核心离子化能量的背景下，评估了与单个，双重激发和三重激发（EOM-CCSDT）的完整运动耦合群集法（EOM-CCSDT）的许多迭代和扰动近似。发现其中几种可以很好地准确地重现EOM-CCSDT能量，尤其是EOM-CCSD*方法，当使用核心价分离（CVS）ANSATZ时，它会以分子大小的第六强度进行严格的缩放。 EOM-CCSDR（3）方法以前已被用来以具有成本效益的方式包含三倍效应，但表现较差，尽管尚未确定确切的原因。这些结果表明，具有第一行原子的分子的非常精确的NexAF和XPS光谱可以以不比EOM-CCSD大的成本计算。
A number of iterative and perturbative approximations to the full equation-of-motion coupled cluster method with single, double, and triple excitations (EOM-CCSDT) are evaluated in the context of calculating the K-edge core-excitation and core-ionization energies of several small molecules. Several of these methods are found to accurately reproduce the full EOM-CCSDT energies well, in particular the EOM-CCSD* method which, when using the core-valence separation (CVS) ansatz, scales rigorously with the sixth power of molecular size. The EOM-CCSDR(3) method, which has been used previously to include triples effects in a cost-effective manner was found to perform rather poorly, although the precise cause has not been determined. These results highlight that very accurate NEXAFS and XPS spectra for molecules with first-row atoms can be computed at a cost not much larger than that for EOM-CCSD.
