Relativistic core–valence-separated molecular mean-field exact-two-component equation-of-motion coupled cluster theory: Applications to L-edge x-ray absorption spectroscopy

Year: 2026

Type: article

Abstract: L-edge x-ray absorption spectra for first-row transition metal complexes are obtained from relativistic equation-of-motion singles and doubles coupled-cluster (EOM-CCSD) calculations that make use of the core–valence separation scheme, with scalar and spin–orbit relativistic effects modeled within the molecular mean-field exact two-component (X2C) framework. By incorporating relativistic effects variationally at the Dirac–Coulomb–Breit reference level, this method delivers accurate predictions of L-edge features, including energy shifts, intensity ratios, and fine-structure splittings, across a range of molecular systems. Benchmarking against perturbative spin–orbit treatments and relativistic TDDFT highlights the superior performance and robustness of the CVS-DCB-X2C-EOM-CCSD approach, including the reliability of basis set recontraction schemes. While limitations remain in describing high-density spectral regions, our results establish CVS-DCB-X2C-EOM-CCSD as a powerful and broadly applicable tool for relativistic core-excitation spectroscopy.

Source: APL Computational Physics

DOI: 10.1063/5.0284813

Authors: Samragni Banerjee, Run R. Li, Brandon C. Cooper, Tianyuan Zhang, Edward F. Valeev, Xiaosong Li, A. Eugene DePrince

Institutions: University of Washington, Florida State University, Virginia Tech

Language: English

Topic: X-ray Spectroscopy and Fluorescence Analysis

Subfield: Radiation

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Funders: National Science Foundation, U.S. Department of Energy, National Energy Research Scientific Computing Center, Office of Science, Office of Advanced Cyberinfrastructure, Basic Energy Sciences, Advanced Scientific Computing Research

OpenAlex ID: W7118236165