We present an extension of the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) theory for computing X-ray L-edge spectra, both in the absorption (XAS) and in the photoelectron (XPS) regimes. The approach is based on the perturbative evaluation of spin–orbit couplings using the Breit–Pauli Hamiltonian and nonrelativistic wave functions described by the fc-CVS-EOM-CCSD ansatz (EOM-CCSD within the frozen-core core–valence separated (fc-CVS) scheme). The formalism is based on spinless one-particle density matrices. The approach is illustrated by modeling XAS and XPS of several model systems ranging from Ar to small molecules containing sulfur and silicon.

中文翻译：

---

用运动方程耦合簇理论对L边缘X射线吸收和光电子能谱进行建模。

我们提出了运动方程耦合簇单双打（EOM-CCSD）理论的扩展，用于在吸收（XAS）和光电子（XPS）体制中计算X射线L边缘光谱。该方法基于使用Breit-Pauli哈密顿量和非相对论波函数对自旋-轨道耦合的扰动评估，fc-CVS-EOM-CCSD ansatz（EOM-CCSD在冻核核心价中分离（fc- CVS）方案）。形式主义基于无旋转的单粒子密度矩阵。通过对从Ar到含硫和硅的小分子的多个模型系统的XAS和XPS进行建模来说明该方法。