Grofe Adam, Li Xiaosong
Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
Phys Chem Chem Phys. 2022 May 11;24(18):10745-10756. doi: 10.1039/d2cp01127a.
In this article, we develop a relativistic exact-two-component nonorthogonal configuration interaction (X2C-NOCI) for computing L-edge X-ray spectra. This article to our knowledge is the first time NOCI has been used for relativistic wave functions. A set of molecular complexes, including SF, SiCl and [FeCl], are used to demonstrate the accuracy and computational scaling of the X2C-NOCI method. Our results suggest that X2C-NOCI is able to satisfactorily capture the main features of the L-edge X-ray absorption spectra. Excitations from the core require a large amount of orbital relaxation to yield reasonable energies and X2C-NOCI allows us to treat orbital optimization explicitly. However, the cost of computing the nonorthogonal coupling is higher than in conventional CI. Here, we propose an improved integral screening using overlap-scaled density combined with a continuous measure of the generalized Slater-Condon rules that allows us to estimate if an element is zero before attempting a two-electron integral contraction.
在本文中，我们开发了一种相对论性精确二分量非正交组态相互作用（X2C-NOCI）方法来计算L边X射线光谱。据我们所知，本文首次将NOCI用于相对论波函数。使用了一组分子配合物，包括SF、SiCl和[FeCl]，来证明X2C-NOCI方法的准确性和计算规模。我们的结果表明，X2C-NOCI能够令人满意地捕捉L边X射线吸收光谱的主要特征。来自核心的激发需要大量的轨道弛豫才能产生合理的能量，而X2C-NOCI使我们能够明确地处理轨道优化。然而，计算非正交耦合的成本高于传统的组态相互作用。在此，我们提出一种改进的积分筛选方法，该方法使用重叠缩放密度并结合广义斯莱特-康登规则的连续度量，使我们能够在尝试进行双电子积分收缩之前估计一个元素是否为零。
