Casanova-Páez Marcos, Neese Frank
Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
J Chem Theory Comput. 2025 Feb 11;21(3):1306-1321. doi: 10.1021/acs.jctc.4c01181. Epub 2025 Jan 28.
X-ray absorption spectroscopy (XAS) is a powerful method for exploring molecular electronic structure by exciting core electrons into higher unoccupied molecular orbitals. In this study, we present the first integration of the spin-unrestricted similarity-transformed equation-of-motion coupled cluster method (CVS-USTEOM-CCSD) for core-excited and core-ionized states into the ORCA quantum chemistry package. Using the core-valence separation (CVS) approach, we evaluate the accuracy of CVS-USTEOM-CCSD across 13 open-shell organic systems, covering over 20 core excitations with diverse spin multiplicities (doublet, triplet, and quartet). The implementation leverages automated active space selection, incorporating CIS natural orbitals to efficiently capture electronic transitions. We benchmark the predicted K- and L-edge spectra against experimental data, underscoring the accuracy of the CVS-USTEOM-CCSD method for high-precision core excitation studies.
X射线吸收光谱法（XAS）是一种通过将内层电子激发到更高的未占据分子轨道来探索分子电子结构的强大方法。在本研究中，我们首次将用于芯激发态和芯电离态的自旋非限制相似变换运动方程耦合簇方法（CVS-USTEOM-CCSD）集成到ORCA量子化学软件包中。使用芯价分离（CVS）方法，我们评估了CVS-USTEOM-CCSD在13个开壳层有机体系中的准确性，涵盖了20多种具有不同自旋多重性（二重态、三重态和四重态）的芯激发。该实现利用自动活性空间选择，结合CIS自然轨道来有效捕获电子跃迁。我们将预测的K边和L边光谱与实验数据进行基准测试，强调了CVS-USTEOM-CCSD方法在高精度芯激发研究中的准确性。
