Tenorio Bruno Nunes Cabral, Voß Torben Arne, Bokarev Sergey I, Decleva Piero, Coriani Sonia
DTU Chemistry - Department of Chemistry, Technical University of Denmark, Kemitorvet Bldg 207, DK-2800 Kongens Lyngby, Denmark.
Institut für Physik, Universität Rostock, Albert-Einstein-Str. 23-24, D-18059 Rostock, Germany.
J Chem Theory Comput. 2022 Jul 12;18(7):4387-4407. doi: 10.1021/acs.jctc.2c00252. Epub 2022 Jun 23.
A methodology to calculate the decay rates of normal and resonant Auger processes in atoms and molecules based on the One-Center Approximation (OCA), using atomic radial Auger integrals, is implemented within the restricted-active-space self-consistent-field (RASSCF) and the multistate restricted-active-space perturbation theory of second order (MS-RASPT2) frameworks, as part of the OpenMolcas project. To ensure an unbiased description of the correlation and relaxation effects on the initial core excited/ionized states and the final cationic states, their wave functions are optimized independently, whereas the Auger matrix elements are computed with a biorthonormalized set of molecular orbitals within the state-interaction (SI) approach. As a decay of an isolated resonance, the computation of Auger intensities involves matrix elements with one electron in the continuum. However, treating ionization and autoionization problems can be overwhelmingly complicated for nonexperts, because of many peculiarities, in comparison to bound-state electronic structure theory. One of the advantages of our approach is that by projecting the intensities on the atomic center bearing the core hole and using precalculated atomic radial two-electron integrals, the Auger decay rates can be easily obtained directly with OpenMolcas, avoiding the need to interface it with external programs to compute matrix elements with the photoelectron wave function. The implementation is tested on the Ne atom, for which numerous theoretical and experimental results are available for comparison, as well as on a set of prototype closed- and open-shell molecules, namely, CO, N, HNCO, HO, NO, and CNH (pyrimidine).
作为OpenMolcas项目的一部分，一种基于单中心近似（OCA）、使用原子径向俄歇积分来计算原子和分子中正常俄歇过程与共振俄歇过程衰减率的方法，在受限活性空间自洽场（RASSCF）和二阶多态受限活性空间微扰理论（MS-RASPT2）框架内得以实现。为确保对初始核心激发/电离态和最终阳离子态的关联与弛豫效应进行无偏描述，它们的波函数被独立优化，而俄歇矩阵元则在态相互作用（SI）方法内用一组双正交归一化分子轨道来计算。作为孤立共振的衰减，俄歇强度的计算涉及连续态中有一个电子的矩阵元。然而，与束缚态电子结构理论相比，由于存在许多特殊性，处理电离和自电离问题对于非专业人士来说可能极其复杂。我们方法的优点之一是，通过将强度投影到带有核心空穴的原子中心，并使用预先计算的原子径向双电子积分，可以直接用OpenMolcas轻松获得俄歇衰减率，而无需将其与外部程序接口以用光电子波函数计算矩阵元。该实现方法在Ne原子上进行了测试，有大量理论和实验结果可供比较，同时也在一组原型闭壳层和开壳层分子上进行了测试，这些分子包括CO、N、HNCO、HO、NO和CNH（嘧啶）。
