The Be K-edge in beryllium oxide and chalcogenides: soft x-ray absorption spectra from first-principles theory and experiment

Olovsson, Weine; Weinhardt, L.; Fuchs, O.; Tanaka, Isao; Puschnig, Peter; Umbach, E.; Heske, Clemens; Draxl, Claudia

doi:10.1088/0953-8984/25/31/315501

Cited by 16 publications

(21 citation statements)

References 51 publications

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“…The first one (λ=1) has a binding energy E b 0.5 eV. This result is comparable with binding energies of core-excitations from the Li and Be K-edge in solids, such as LiS 2 [30] and BeS [32]. Conversely, near-edge core-excitons in organic systems exhibit larger binding energies, in the order of a few eV [43].…”

Section: B Core-level Absorption Spectrum From the O K-edgementioning

confidence: 74%

“…Within this method, the e-h Coulomb interaction is taken into account self-consistently at the density-functional theory (DFT) level, yielding good results for deep core excitations, where correlation effects are not prominent [29]. On the other hand, this method is known to perform worse for excitations from shallow core or semicore states, where e-h correlation becomes relevant [29][30][31][32]. In the core-hole approximation, the exciton binding strength relies on the adopted approximation for the exchange-correlation functional [33].…”

Section: B Theoretical Backgroundmentioning

confidence: 99%

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Atomic signatures of local environment from core-level spectroscopy inβ−Ga2O3

et al. 2016

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We present a joint theoretical and experimental study on core-level excitations from the oxygen K-edge of β-Ga 2 O 3 . A detailed analysis of the electronic structure reveals the importance of O-Ga hybridization effects in the conduction region. The spectrum from O 1s core electrons is dominated by excitonic effects, which overall red-shift the absorption onset by 0.5 eV, and significantly redistribute the intensity to lower energies. Analysis of the spectra obtained within many-body perturbation theory reveals atomic fingerprints of the inequivalent O atoms. From the comparison of energy-loss near-edge fine-structure (ELNES) spectra computed with respect to different crystal planes, with measurements recorded under the corresponding diffraction conditions, we show how the spectral contributions of specific O atoms can be enhanced while quenching others. These results suggest ELNES, combined with ab initio many-body theory, as a very powerful technique to characterize complex systems, with sensitivity to individual atomic species and to their local environment.

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Section: B Core-level Absorption Spectrum From the O K-edgementioning

confidence: 74%

Section: B Theoretical Backgroundmentioning

confidence: 99%

Atomic signatures of local environment from core-level spectroscopy inβ−Ga2O3

et al. 2016

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“…However, most of the schemes proposed so far are either based on pseudo-potential approximation [21,22], or, in an all-electron framework, on the description of the core states in terms of local orbitals as part of the valence region, neglecting spin-orbit coupling. While the latter choice turned out to be effective in many cases [18,[23][24][25][26], this approximate treatment of core states is limited to a specific energy window and initial states. In particular, excitations from core levels with a non-negligible spin-orbit splitting need a relativistic treatment, even for low transition energies.…”

Section: Introductionmentioning

confidence: 99%

Addressing electron-hole correlation in core excitations of solids: An all-electron many-body approach from first principles

2017

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We present an ab initio study of core excitations of solid-state materials focusing on the role of electron-hole correlation. In the framework of an all-electron implementation of many-body perturbation theory into the exciting code, we investigate three different absorption edges of three materials, spanning a broad energy window, with transition energies between a few hundred to thousands of eV. Specifically, we consider excitations from the Ti K edge in rutile and anatase TiO2, from the Pb M4 edge in PbI2, and from the Ca L2,3 edge in CaO. We show that the electronhole attraction rules x-ray absorption for deep core states, when local fields play a minor role. On the other hand, the local-field effects introduced by the exchange interaction between the excited electron and the hole dominate excitation processes from shallower core levels, separated by a spin-orbit splitting of a few eV. Our approach yields absorption spectra in good agreement with available experimental data, and allows for an in-depth analysis of the results, revealing the electronic contributions to the excitations, as well as their spatial distribution.

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“…This is in particular true for the description of optical spectroscopy in the UV and visible light range [27,28], with several BSE calculations appearing recently for bulk and single layers of h-BN [29,30]. Furthermore, few publications on different materials employing the BSE for the calculation of x-ray absorption spectra have been published [26,[31][32][33][34][35][36]. Already in 1998 and 1999, boron K edges and resonant inelastic x-ray scattering (RIXS) calculations using the BSE were reported [37][38][39][40], although these early calculations might not have been fully converged with respect to the computational parameters.…”

Section: Introductionmentioning

confidence: 99%

Effects of electron-phonon coupling on absorption spectrum: K edge of hexagonal boron nitride

et al. 2018

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A detailed analysis of the theoretical x-ray absorption near-edge structures (XANES) for the boron and nitrogen K edge in hexagonal boron nitride (h-BN) employing density-functional theory calculations is presented. The supercell core-hole method and the Bethe-Salpeter equation are used for the description of electron-hole interactions. The calculations are carried out with two different codes, the VASP and the WIEN2K codes, employing the projector augmented-wave and the full-potential linear augmented-plane-wave methods, respectively. We find close agreement between spectra obtained from the two codes and between calculations using the supercell core-hole method and the Bethe-Salpeter approach. All our calculations, as well as previous calculations using the ground-state structure, yield a single 2p σ * peak in the boron K-edge spectrum and hence fail to describe the experimental double-peak structure. We find that the inclusion of electron-phonon interactions is crucial to obtain the experimentally observed double-peak structure. We include these effects fully parameter free and ab initio using a one-shot sampling method and obtain excellent agreement with experiment.

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The Be K-edge in beryllium oxide and chalcogenides: soft x-ray absorption spectra from first-principles theory and experiment

Cited by 16 publications

References 51 publications

Atomic signatures of local environment from core-level spectroscopy inβ−Ga2O3

Atomic signatures of local environment from core-level spectroscopy inβ−Ga2O3

Addressing electron-hole correlation in core excitations of solids: An all-electron many-body approach from first principles

Effects of electron-phonon coupling on absorption spectrum: K edge of hexagonal boron nitride

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