Issue 18, 2022

Relativistic nonorthogonal configuration interaction: application to L2,3-edge X-ray spectroscopy

Abstract

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 SF6, SiCl4 and [FeCl6]3−, 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 L2,3-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.

Graphical abstract: Relativistic nonorthogonal configuration interaction: application to L2,3-edge X-ray spectroscopy

Supplementary files

Article information

Article type
Paper
Submitted
07 mar 2022
Accepted
12 apr 2022
First published
22 apr 2022

Phys. Chem. Chem. Phys., 2022,24, 10745-10756

Author version available

Relativistic nonorthogonal configuration interaction: application to L2,3-edge X-ray spectroscopy

A. Grofe and X. Li, Phys. Chem. Chem. Phys., 2022, 24, 10745 DOI: 10.1039/D2CP01127A

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