Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 53: Poster Electronic Structure Theory

O 53.2: Poster

Tuesday, March 18, 2025, 18:00–20:00, P2

First-Principles Calculations of X-ray Absorption Spectra: Supercell Core-Hole Method versus Bethe-Salpeter Equation — •Ziyu Wang¹, Lu Qiao¹, Ronaldo Rodrigues Pelá², and Claudia Draxl¹ — ¹Physics Department and CSMB, Humboldt-Universität zu Berlin, Zum Großen Windkanal 2, 12489 Berlin, Germany — ²Supercomputing Department, Zuse Institute Berlin (ZIB), Berlin, Takustraße 7, 14195 Berlin, Germany

Accurate simulations of X-ray absorption spectra (XAS) are essential for understanding core-level excitations and electronic structure. In this study, we compare two approaches for calculating XAS: the supercell core-hole (SCH) method based on density-functional theory and the Bethe-Salpeter equation (BSE) of many-body perturbation theory. In the SCH method, core excitations are simulated by removing a core electron from the system, thus treating electron-hole interaction on the DFT level. In contrast, excitonic effects are considered explicitly in the two-body Hamiltonian underlying the BSE. We apply the SCH method with various exchange-correlation (xc) functionals of DFT to calculate XAS in diverse materials (metals, semiconductors, and insulators) and absorption edges. By comparing them with XAS obtained from BSE, we evaluate in which cases the SCH method is appropriate to be applied.

Keywords: Supercell core-hole; Bethe Salpeter Equation; Core-hole screening