Angular-Dependence in the K Pre-Edge XANES of Cubic Crystals : The Separation of the Empty Metal e<sub>g</sub>and t<sub>2g</sub>States of NiO and FeO

Heumann, D.; Dräger, G.; Bocharov, S.

doi:10.1051/jp4/1997060

Cited by 22 publications

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“…For the further study two spectra at such sample orientations were selected, that one of the components e g or t 2g brings its whole contribution, while the contribution of the other is zero [8].…”

Section: Methodsmentioning

confidence: 99%

“…According to Ref. [8], the ligand-field split t 2g and e g conduction bands consisting of Ni3d-O2p antibonding MOs are disposed above the filled valence bands consisting of O2p-Ni 3d bonding MOs. Each conduction band is split by exchange interaction into low-energy and highenergy subbands.…”

Section: Electronic Structure Of Antiferromagnetic Nio and The Clustementioning

confidence: 99%

“…The second mechanism is the well-known quadrupole transition mechanism, which allows direct transitions of the TM 1s electrons to the e g and t 2g MOs of the TMO 6 octahedron containing the absorbing TM atom. Despite their weak intensities for the light TM atoms the peaks caused by this mechanism can be unambiguously identified in the experimental spectra owing to the specific dependence of their areas on the direction and polarization of incident photons [7][8][9]. The e g and t 2g MOs of the TMO 6 octahedron containing the absorbing TM atom are highly localized within the atomic sphere and, therefore, these MOs are strongly shifted down by the K-hole potential.…”

Section: Introductionmentioning

confidence: 99%

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Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Vedrinskiǐ

Крайзман

Novakovich

et al. 2001

phys. stat. sol. (b)

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Polarized Ni K XANES of single crystal NiO is studied experimentally and theoretically for two crystal orientations relative to the polarization and wave vectors of incident X-ray beam. The spectra calculated by the full multiple scattering method for a spin-dependent cluster potential and incomplete screening of the core hole appear to be in an excellent agreement with the experiment. The low energy pre-edge peak is shown to be caused by the quadrupole transitions of the Ni 1s electron to an exciton-type state shifted down by $4 eV from the empty e g high-energy conduction band under the influence of the core hole potential. The feature caused by the Ni 1s ! e g band dipole transitions is also recognized in the spectrum. It is shown that the same mechanisms, which are responsible for the formation of the pre-edge fine structure in the oxides of early 3d-metals in 3d 0 state, work in the considered case as well. A comparative analysis outlining the significance of different mechanisms for the pre-edge structure formation in cases of early and late 3d-metal spectra is presented. The antiferromagnetic order of the absorber is taken into account within oneelectron approximation.Die polarisierte Ni K XANES von einkristallinem NiO wurde experimentell und theoretisch fü r zwei Kristallorientierungen relativ zum Polarisations-und Wellenvektor des einfallenden Rö ntgenstrahls untersucht. Die Spektren wurden nach der Full-multiple-scattering Methode fü r ein spinabhä ngiges Clusterpotential und fü r unvollstä ndige Abschirmung des Rumpfloches in exzellenter Ûbereinstimmung mit dem Experiment berechnet. Die niederenergetische Vorkantenabsorption wird durch Quadrupolü bergä nge von Ni 1s Elektronen in einen exzitonä hnlichen Zustand erklä rt, der durch das Rumpflochpotential um $4 eV gegenü ber dem unbesetzten e gartigen Leitungsband abgesenkt ist. Die aus den Ni 1s ! e g Dipolü bergä ngen berechneten Strukturen sind auch in den experimentellen Spektren zu erkennen. Es wird gezeigt, da im vorliegenden Fall die gleichen Mechanismen wirken, die auch fü r das Auftreten der Vorkantenabsorption bei den frü hen 3d-Metalloxiden im 3d 0 -Zustand verantwortlich sind. Eine vergleichende Analyse der Bedeutung der verschiedenen Mechanismen fü r das Entstehen der Vorkantenstruktur bei den Verbindungen der 3d-Metalle niedriger und hö herer Ordnungszahl wird durchgefü hrt.

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Section: Methodsmentioning

confidence: 99%

Section: Electronic Structure Of Antiferromagnetic Nio and The Clustementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Vedrinskiǐ

Крайзман

Novakovich

et al. 2001

phys. stat. sol. (b)

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“…Four different contributions are visible. Peaks 1 and 2, centered respectively at 7112.65 and 7114.05 eV, are related to 1s → 3d (quadrupolar) and/or 1s → 4p (dipolar) metal electronic transitions [35,54,55]. Contributions 3 and 4 centered above 7115.0 eV (7115.34 and 7116.88 eV) are due to extra transitions involving 3d orbitals of distant iron neighbors [35].…”

Section: Al Mas Nmr Al K-edge Xafsmentioning

confidence: 99%

Evolution of Fe species during the synthesis of over-exchanged Fe/ZSM5 obtained by chemical vapor deposition of FeCl3

Battiston

Bitter

Groot

et al. 2003

Journal of Catalysis

164

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The evolution of iron in over-exchanged Fe/ZSM5 prepared via chemical vapor deposition of FeCl 3 was studied at each stage of the synthesis. Different characterization techniques (EXAFS, HR-XANES, 57 Fe Mössbauer spectroscopy, 27 Al NMR, EELS, HR-TEM, XRD, N 2 physisorption, and FTIR spectroscopy) were applied in order to correlate the changes occurring in the local environment of the Fe atoms with migration and aggregation phenomena of iron at micro-and macroscopic scale. Mononuclear isolated Fe-species are formed upon FeCl 3 sublimation, which are transformed into binuclear Fe-complexes during washing. During calcination, iron detached from the Brønsted sites migrates to the external surface of the zeolite, finally leading to significant agglomeration. Nevertheless, agglomeration of Fe can be strongly suppressed by adequately tuning the conditions of the calcination.  2002 Elsevier Science (USA). All rights reserved.

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“…The oxidation state of iron and its local environment in a mildly calcined Fe/ZSM5 sample have been monitored during heating treatments in He and O 2 , by combining the results of in situ EXAFS and high-resolution (HR)-XANES. The HR-XANES of the Fe K edge, especially the pre-edge feature (related to 1s → 3d metal electronic transitions [32][33][34]), provides detailed information on both the oxidation state of iron and the coordination geometry [35]. This information can be used as input for the analysis of the EXAFS data.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Fe-binuclear complexes in over-exchanged Fe/ZSM5, studied by in situ XAFS spectroscopy Part 1: Heat treatment in He and O2

Battiston

Bitter

Heijboer

et al. 2003

Journal of Catalysis

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Angular-Dependence in the K Pre-Edge XANES of Cubic Crystals : The Separation of the Empty Metal e_gand t_2gStates of NiO and FeO

Cited by 22 publications

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Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Evolution of Fe species during the synthesis of over-exchanged Fe/ZSM5 obtained by chemical vapor deposition of FeCl3

Reactivity of Fe-binuclear complexes in over-exchanged Fe/ZSM5, studied by in situ XAFS spectroscopy Part 1: Heat treatment in He and O2

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Angular-Dependence in the K Pre-Edge XANES of Cubic Crystals : The Separation of the Empty Metal egand t2gStates of NiO and FeO

Cited by 22 publications

References 0 publications

Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Evolution of Fe species during the synthesis of over-exchanged Fe/ZSM5 obtained by chemical vapor deposition of FeCl3

Reactivity of Fe-binuclear complexes in over-exchanged Fe/ZSM5, studied by in situ XAFS spectroscopy Part 1: Heat treatment in He and O2

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Angular-Dependence in the K Pre-Edge XANES of Cubic Crystals : The Separation of the Empty Metal e_gand t_2gStates of NiO and FeO