Oxygen x-ray emission and absorption spectra as a probe of the electronic structure of strongly correlated oxides

Kurmaev, E.Z.; Wilks, Regan G.; Moewes, A.; Finkelstein, L. D.; Shamin, S. N.; Kuneš, J.

doi:10.1103/physrevb.77.165127

Cited by 159 publications

(161 citation statements)

References 21 publications

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“…Stronger changes in the XAS compared to XES are expected, as the formally empty 3d shell of the Ti 4þ ions means there are no occupied d states to contribute to the XES whereas there are ample empty states to contribute to the XAS. The conduction band minimum (CB min ) and valence band maximum (VB max ) can be extracted from the XAS and XES using the second derivative technique, 29 and from these values the electronic band gap can be estimated. The second derivatives of the SiO 2 and SiO 2 :TiO 2 spectra are shown at the bottom of Figure 4.…”

Section: Methodsmentioning

confidence: 99%

The formation of Ti–O tetrahedra and band gap reduction in SiO2 via pulsed ion implantation

Green

Zatsepin

Hunt

et al. 2013

Journal of Applied Physics

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Titanium ions are implanted into amorphous SiO 2 at two different fluences using pulsed ion implantation, and the resulting samples are annealed. Bulk sensitive soft X-ray absorption spectroscopy of the Ti L 2;3 edge reveal strikingly different spectra for the two fluences. Spectral simulations using multiplet crystal field theory show clearly that for low fluence the Ti ions have a local octahedral coordination, while at higher fluence the formation of Ti 4þ -O tetrahedra dominates. Using O K-edge X-ray absorption and emission, the effect of the Ti states on the valence and conduction bands of the host SiO 2 is revealed. With the introduction of Ti tetrahedra, the band gap reduces from about 8 eV to just over 4 eV, due entirely to the Ti 3d conduction band states. These results demonstrate the possibility to obtain Ti-O tetrahedra in silica by Ti ion implantation and a suitable thermal treatment, clarify the mechanism of band gap reduction with Ti doping in SiO 2 , and demonstrate the sensitivity of L-edge X-ray absorption with a multiplet crystal field theory analysis to the Ti coordination of novel materials. V C 2013 American Institute of Physics. [http://dx

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Section: Methodsmentioning

confidence: 99%

The formation of Ti–O tetrahedra and band gap reduction in SiO2 via pulsed ion implantation

Green

Zatsepin

Hunt

et al. 2013

Journal of Applied Physics

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“…Lastly, we compare the partial density of states of the oxygen 2p electrons with recently reported oxygen x-ray emission spectroscopy and x-ray absorption spectroscopy (XES-XAS) measurements 49 on MnO, CoO and NiO, in Fig. 3.…”

Section: Comparison With Xes-xas Spectramentioning

confidence: 99%

Accurate screened exchange band structures for the transition metal monoxides MnO, FeO, CoO and NiO

Gillen¹,

Robertson²

2013

J. Phys.: Condens. Matter

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We report calculations of the band structures and density of states of the four transition metal monoxides MnO, FeO, CoO and NiO using the hybrid density functional sX-LDA. Late transition metal oxides are prototypical examples of strongly correlated materials, which pose challenges for electronic structure methods. We compare our results with available experimental data and show that our calculations generally yield accurate predictions for the fundamental band gaps and valence bands, in favourable agreement with previously reported theoretical studies. For MnO, the band gaps are still underestimated, suggesting additional many-body effects that are not captured by our screened hybrid functional approach.

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“…123 In our calculations we do not explicitly create a core hole, whose effect is expected to be small for oxygen emission and absorption spectra. 123,130 We also do not consider the influences of absorption cross sections. These two facts combined mean that only a comparison of peak positions and not relative intensities is meaningful.…”

Section: Comparisons With Experimentsmentioning

confidence: 99%

First-principles modeling of localizeddstates with theGW@LDA+Uapproach

et al. 2010

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First-principles modeling of systems with localized d states is currently a great challenge in condensedmatter physics. Density-functional theory in the standard local-density approximation ͑LDA͒ proves to be problematic. This can be partly overcome by including local Hubbard U corrections ͑LDA+ U͒ but itinerant states are still treated on the LDA level. Many-body perturbation theory in the GW approach offers both a quasiparticle perspective ͑appropriate for itinerant states͒ and an exact treatment of exchange ͑appropriate for localized states͒, and is therefore promising for these systems. LDA+ U has previously been viewed as an approximate GW scheme. We present here a derivation that is simpler and more general, starting from the static Coulomb-hole and screened exchange approximation to the GW self-energy. Following our previous work for f-electron systems ͓H. Jiang, R. I. Gomez-Abal, P. Rinke, and M. Scheffler, Phys. Rev. Lett. 102, 126403 ͑2009͔͒ we conduct a systematic investigation of the GW method based on LDA+ U͑GW @LDA+U͒, as implemented in our recently developed all-electron GW code FHI-gap ͑Green's function with augmented plane waves͒ for a series of prototypical d-electron systems: ͑1͒ ScN with empty d states, ͑2͒ ZnS with semicore d states, and ͑3͒ late transition-metal oxides ͑MnO, FeO, CoO, and NiO͒ with partially occupied d states. We show that for ZnS and ScN, the GW band gaps only weakly depend on U but for the other transition-metal oxides the dependence on U is as strong as in LDA+ U. These different trends can be understood in terms of changes in the hybridization and screening. Our work demonstrates that GW @LDA+U with "physical" values of U provides a balanced and accurate description of both localized and itinerant states.

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Oxygen x-ray emission and absorption spectra as a probe of the electronic structure of strongly correlated oxides

Cited by 159 publications

References 21 publications

The formation of Ti–O tetrahedra and band gap reduction in SiO2 via pulsed ion implantation

The formation of Ti–O tetrahedra and band gap reduction in SiO2 via pulsed ion implantation

Accurate screened exchange band structures for the transition metal monoxides MnO, FeO, CoO and NiO

First-principles modeling of localizeddstates with theGW@LDA+Uapproach

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