Huang Meng, Evangelista Francesco A
Department of Chemistry and Cherry Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, United States.
J Chem Theory Comput. 2024 Sep 13;20(18):7990-8000. doi: 10.1021/acs.jctc.4c00835.
X-ray photoelectron spectroscopy (XPS) is a powerful experimental technique for probing the electronic structure of molecules and materials; however, interpreting XPS data requires accurate computational methods to model core-ionized states. This work proposes and benchmarks a new approach based on the generalized active space-driven similarity renormalization group (GAS-DSRG) for calculating core-ionization energies and treating correlation effects at the perturbative and nonperturbative levels. We tested the GAS-DSRG across three data sets. First, the vertical core-ionization energies of small molecules containing first-row elements are evaluated. GAS-DSRG achieves mean absolute errors below 0.3 eV, which is comparable to high-level coupled cluster methods. Next, the accuracy of GAS-DSRG is evaluated for larger organic molecules using the CORE65 data set, with the DSRG-MRPT3 level yielding a mean absolute error of only 0.34 eV for 65 core-ionization transitions. Insights are provided into the treatment of static and dynamic correlation, the importance of high-order perturbation theory, and notable differences from density functional theory in the predicted energy ordering of core-ionized states for specific molecules. Finally, vibrationally resolved XPS spectra of diatomic molecules (CO, N, and O) are simulated, showing excellent agreement with experimental data.
X射线光电子能谱（XPS）是一种用于探测分子和材料电子结构的强大实验技术；然而，解释XPS数据需要精确的计算方法来模拟芯离子化态。这项工作提出并基准测试了一种基于广义活性空间驱动相似重整化群（GAS-DSRG）的新方法，用于计算芯电离能并在微扰和非微扰水平上处理相关效应。我们在三个数据集上测试了GAS-DSRG。首先，评估了含第一行元素的小分子的垂直芯电离能。GAS-DSRG实现了低于0.3 eV的平均绝对误差，这与高水平耦合簇方法相当。接下来，使用CORE65数据集评估了GAS-DSRG对更大有机分子的准确性，DSRG-MRPT3水平对于65个芯电离跃迁产生的平均绝对误差仅为0.34 eV。深入探讨了静态和动态相关性的处理、高阶微扰理论的重要性，以及在特定分子芯离子化态预测能量排序方面与密度泛函理论的显著差异。最后，模拟了双原子分子（CO、N和O）的振动分辨XPS光谱，与实验数据显示出极好的一致性。
