Density functional theory for core-level X-ray absorption

2025/11/22 by An, Seokkyu, Ozaki, Taisuke
Physics and Astronomy · #Advanced X-ray Imaging Techniques #Crystallography and Radiation Phenomena #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #X-ray Spectroscopy and Fluorescence Analysis

paper · doi:10.48550/arxiv.2511.17969

openalex publication_date 2025/11/22 · openalex created_date 2025/11/27 · openalex updated_date 2026/07/28

Abstract

We establish a rigorous density functional theory (DFT) framework for core-level X-ray absorption spectroscopy (XAS) by formulating a constrained search for core-excited states based on the Gunnarsson-Lundqvist theorem. Within this framework, the explicit-core Delta SCF scheme enables shift-free absolute edge alignment and a consistent treatment of L/M edges with spin-orbit-resolved projectors. In addition, by exploiting dipole selection rules, we recast the evaluation of the dipole matrix elements, which otherwise requires many independent Slater determinant calculations, into a compact single determinant form. This reduces the computational scaling from O(N⁴) to O(N³), where N is the number of electrons, without introducing additional approximations. Across representative C, B, O, and Li K-edge benchmarks in molecules and solids, the method reproduces line shapes, polarization anisotropies, and absolute onsets without empirical shifts, providing a robust and scalable route to quantitatively reliable XAS simulations within DFT.

Citations

• Surface structure of the 3x3-Si phase on Al(111), studied by the multiple usages of positron diffraction and core-level photoemission spectroscopy
• A three-dimensional domain decomposition method for large-scale DFT electronic structure calculations
• Exchange and correlation in atoms, molecules, and solids by the spin-density-functional formalism

Related

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• Extending Orbital-Optimized Density Functional Theory to L-Edge XPS and Beyond: Spin–Orbit Coupling via Nonorthogonal Quasi-Degenerate Perturbation Theory
• Development of XAFS theory