{"title":"Core-Excited States for Open-Shell Systems in Similarity-Transformed Equation-of-Motion Theory.","authors":"Marcos Casanova-Páez, Frank Neese","doi":"10.1021/acs.jctc.4c01181","DOIUrl":null,"url":null,"abstract":"<p><p>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.</p>","PeriodicalId":45,"journal":{"name":"Journal of Chemical Theory and Computation","volume":" ","pages":"1306-1321"},"PeriodicalIF":5.7000,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11823418/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Chemical Theory and Computation","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1021/acs.jctc.4c01181","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/1/28 0:00:00","PubModel":"Epub","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
摘要
X 射线吸收光谱（XAS）是一种通过激发核心电子进入较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，我们首次将针对核激发态和核电离态的自旋无限制相似性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。利用核价分离（CVS）方法，我们评估了 CVS-USTEOM-CCSD 在 13 个开壳有机体系中的准确性，涵盖了 20 多种具有不同自旋倍率（二重、三重和四重）的核激发。该方法利用自动活动空间选择，结合 CIS 自然轨道，有效捕捉电子跃迁。我们将预测的 K 边和 L 边光谱与实验数据进行了比对，从而证明了 CVS-USTEOM-CCSD 方法在高精度核激发研究中的准确性。
Core-Excited States for Open-Shell Systems in Similarity-Transformed Equation-of-Motion Theory.
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.
期刊介绍：
The Journal of Chemical Theory and Computation invites new and original contributions with the understanding that, if accepted, they will not be published elsewhere. Papers reporting new theories, methodology, and/or important applications in quantum electronic structure, molecular dynamics, and statistical mechanics are appropriate for submission to this Journal. Specific topics include advances in or applications of ab initio quantum mechanics, density functional theory, design and properties of new materials, surface science, Monte Carlo simulations, solvation models, QM/MM calculations, biomolecular structure prediction, and molecular dynamics in the broadest sense including gas-phase dynamics, ab initio dynamics, biomolecular dynamics, and protein folding. The Journal does not consider papers that are straightforward applications of known methods including DFT and molecular dynamics. The Journal favors submissions that include advances in theory or methodology with applications to compelling problems.
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