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Titolo:
Density-functional modelling of core-hole effects in electron energy-loss near-edge spectra
Autore:
Elsasser, C; Kostlmeier, S;
Indirizzi:
Max Planck Inst Met Forsch, D-70174 Stuttgart, Germany Max Planck Inst MetForsch Stuttgart Germany D-70174 Stuttgart, Germany
Titolo Testata:
ULTRAMICROSCOPY
fascicolo: 3-4, volume: 86, anno: 2001,
pagine: 325 - 337
SICI:
0304-3991(200102)86:3-4<325:DMOCEI>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
X-RAY-ABSORPTION; GROUND-STATE PROPERTIES; FINE-STRUCTURE; LOSS SPECTROSCOPY; MANY-ELECTRON; METALS; TIS2; MGO;
Keywords:
density functional theory; band-structure calculations; magnesium oxide; electron energy loss spectroscopy; energy-loss near-edge structures; core-hole effects;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
24
Recensione:
Indirizzi per estratti:
Indirizzo: Elsasser, C Max Planck Inst Met Forsch, Seestr 92, D-70174 Stuttgart, Germany Max Planck Inst Met Forsch Seestr 92 Stuttgart Germany D-70174
Citazione:
C. Elsasser e S. Kostlmeier, "Density-functional modelling of core-hole effects in electron energy-loss near-edge spectra", ULTRAMICROS, 86(3-4), 2001, pp. 325-337

Abstract

A series of (MgO)(n) supercells (n = 1,4, 8, 16, 32) with three-dimensional periodic boundary conditions is investigated by density-functional band-structure calculations. The influence of supercell size and shape on calculated electron energy-loss near-edge spectra is assessed quantitatively, employing the Z + 1 approximation for the representation of final-state effects. Relevant convergence criteria are the length scale set by the spatial extension of the valence-electron screening cloud around the core hole and theinteraction energy of neighbouring core-hole centres. A sufficient supercell size provided, the Z + 1 approximation yields a highly satisfactory description of excitations from the Is shell of light elements, such as Mg and O, compared to experimental data. For comparison, pseudopotentials for excited states were generated for Mg, both with a large core (Is, 2s, 2p orbitals) and a small core (Is orbital only) included into the pseudopotential. The corresponding calculations with frozen core holes lead to very good agreement with the results from the Z + 1 calculation for the Is excitations. The explicit treatment of the subvalence shell (2s, 2p), however, is mandatory for the proper modelling of excitations from orbitals higher than 1s. This indicates that the core polarisability plays an important role in excitations from more extended shells. (C) 2001 Elsevier Science B.V. All rights reserved.

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Documento generato il 26/09/20 alle ore 05:32:49