First-principles calculation of resonant x-ray emission spectra applied to ZnO

The electronic structure and band dispersion of graphene on SiO2 have been studied by X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). Using first-principles calculations, it is found that the core-hole effect is dramatic in XAS while it has negligible consequences in XES. Strong dispersive features, due to the conservation of crystal momentum are observed in RIXS spectra. Simulated RIXS spectra based on the Kramers-Heisenberg theory agree well with the experimental results, provided a shift between RIXS and XAS due to the absence/presence of the core hole is taken into account.

show abstract

“…The kconserving parts or coherent RIXS spectra were calculated in the Kramers-Heisenberg formalism as described in ref. [31]. …”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Electronic band structure of graphene from resonant soft x-ray spectroscopy: The role of core-hole effects

et al. 2012

Self Cite

View full text Add to dashboard Cite

show abstract

“…III above. Note, however, that selfconsistency of the wave-functions did not resolve the problem of the too high Zn-d energies in ZnO [13,37]. Thus, a universal ab initio GW approach for TM compounds is not yet available, and may require addressing simultaneously a number of separate issues, such as vertex corrections and excitonic effects, the use of PAW potentials with improved scattering properties at high energies, or the treatment of deeper semi-core states as valence electrons, all of which increase the computational overhead.…”

Section: Fig 2 (A)mentioning

confidence: 99%

“…While the self-consistency in the wavefunctions significantly improves the band structure in Cu 2 O (Ref. [24,28], see also below), it does not correct the d-band position in ZnO [13,37]. Possible improvements may further result from excitonic effects (vertex corrections), or from improvements or more technical nature, such as the use of PAW potentials that have been specifically generated so to yield better scattering properties at very high energies [20], or the inclusion of more semi-core states being explicitly treated as valence electrons.…”

Section: Band Gaps Of 3d Oxides In Baseline Gw Calculationsmentioning

confidence: 99%

“…The G 0 W 0 (LDA) variant, which underestimates the gap of ZnO by as much as 1 eV [7,22], already overestimates the gap by 0.3 eV in TiO 2 [30] and by 0.6 eV in SrTiO 3 [36]. The self-consistency in the wave-functions was found to be essential for the correct band-structure of Cu 2 O [24,28], but in ZnO and GaN, the self-consistency did not correct the underbinding of the 3d states [13,37]. Thus, the purpose of the present study is to establish the trends along the 3d series of TM oxides in a single GW scheme.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Band-structure calculations for the 3dtransition metal oxides inGW

2013

View full text Add to dashboard Cite

Many-body GW calculations have emerged as a standard for the prediction of band-gaps, bandstructures, and optical properties for main-group semiconductors and insulators, but it is not well established how predictive the GW method is in general for transition metal (TM) compounds. Surveying the series of 3d oxides within a typical GW approach using the random phase approximation reveals mixed results, including cases where the calculated band gap is either too small or too large, depending on the oxidation states of the TM (e.g., FeO/Fe 2 O 3 , Cu 2 O/CuO). The problem appears to originate mostly from a too high average d-orbital energy, whereas the splitting between occupied and unoccupied dsymmetries seems to be reasonably accurate. It is shown that augmenting the GW self-energy by an attractive (negative) and occupation-independent on-site potential for the TM d-orbitals with a single parameter per TM cation can reconcile the band gaps for different oxide stoichiometries and TM oxidations states. In Cu 2 O, which is considered here in more detail, standard GW based on wavefunctions from initial density or hybrid functional calculations yields an unphysical prediction with an incorrect ordering of the conduction bands, even when the magnitude of the band gap is in apparent agreement with experiment. The correct band ordering is restored either by applying the d-state potential or by iterating the wave functions to self-consistency, which both have the effect of lowering the Cu-d orbital energy. While it remains to be determined which improvements over standard GW implementations are needed to achieve an accurate ab initio description for a wide range of transition metal compounds, the application of the empirical on-site potential serves to mitigate the problems specifically related to d-states in GW calculations.2

show abstract

“…To obtain the best possible band structure for the ZnO sodalite (cf. Figure 1), we have to go beyond these methods [22,23]. In this work, we used a state-of-the-art approach based on a restricted self-consistent (sc) GW scheme.…”

mentioning

confidence: 99%

pDoping in Expanded Phases of ZnO: AnAb InitioStudy

et al. 2012

View full text Add to dashboard Cite

The issue of p doping in nanostructured cagelike ZnO is investigated by state-of-the-art calculations. Our study is focused on one prototypical structure, namely, sodalite, for which we show that p-type doping is possible for elements of the V, VI, and VII columns of the periodic table. However, some dopants tend to form dimers, thus impairing the stability of this kind of doping. This difference of behavior is discussed, and two criteria are proposed to ensure stable p doping.

show abstract

First-principles calculation of resonant x-ray emission spectra applied to ZnO

Cited by 11 publications

References 25 publications

Electronic band structure of graphene from resonant soft x-ray spectroscopy: The role of core-hole effects

Electronic band structure of graphene from resonant soft x-ray spectroscopy: The role of core-hole effects

Band-structure calculations for the 3dtransition metal oxides inGW

pDoping in Expanded Phases of ZnO: AnAb InitioStudy

Contact Info

Product

Resources

About