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DS: Fachverband Dünne Schichten
DS 23: Frontiers in Electronic-Structure Theory - Focus on Electron-Phonon Interactions III (joint session O/CPP/DS/HL)
DS 23.6: Vortrag
Mittwoch, 18. März 2020, 12:00–12:15, GER 38
Optical and x-ray absorption spectra of MgO from first-principles including many-body effects — •Vijaya Begum, Markus E Gruner, and Rossitza Pentcheva — Faculty of Physics and Centre for Nanointegration (CENIDE), University of Duisburg-Essen, Duisburg, Germany
We discuss the optical and x-ray absorption (XAS) spectra of MgO − a wide band gap oxide with versatile applications − in the framework of density functional theory (DFT) including many-body and excitonic corrections. The quasi-particle band gap improves over DFT with PBEsol as the starting exchange-correlation functional (4.58 → 7.52 eV) and is overcorrected with the hybrid functional HSE06 (6.58 → 8.53 eV) when compared to experiment (7.7 eV). Including excitonic effects by solving the Bethe-Salpeter equation (BSE) leads to excellent agreement with the experimental spectrum both for the real and imaginary part of the dielectric function, when starting with the HSE06 functional. Furthermore, the x-ray absorption spectra of the O and Mg K-edge calculated with the Exciting code exhibit good agreement with experiment regarding the positions of the prominent peaks, underlining the importance of including the core-hole and electron interactions within the G0W0+BSE. Projection of the electron-hole coupling coefficients from the BSE eigenvectors on the band structure allows to explore the origin of the peaks and identify the orbital character of the relevant contributions.
Funding by DFG CRC1242, project C02 is gratefully acknowledged.