Charge-ordered spinel AlV<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>: High-energy-resolution EELS and computational studies

Prytz, Øystein; Flage−Larsen, Espen; Gu, Lin; Sigle, Wilfried; Aken, Peter A. van; Taftø, J.

doi:10.1103/physrevb.85.195112

Cited by 10 publications

(7 citation statements)

References 33 publications

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“…The oxygen K-edges show a three peak structure with peaks at 538(±1), 541(±1) and 546(±1) eV. These edge values compare well with the earlier observed [11] O K edge energies at 535, 540 and 545 eV and V-L 3 and V-L 2 peaks at 519 and 527 eV. The difference observed in the O 1s to hybridized 3 e g peak at 538(±1) eV from the literature quoted value (535 eV) is considered acceptable within the statistics [18].…”

Section: Resultssupporting

confidence: 90%

“…The charge on Al remains the same in the cubic and in the rhombohedral phases. Very recently electron energy loss spectroscopy (EELS) measurements on AlV 2 O 4 [11] have estimated the average value of charge on vanadium to be 2.5 + . Thus, presently, there appears to be convergence on the heptamer structural model, but a consensus has yet to emerge on the assignment of charges on vanadium.…”

Section: Introductionmentioning

confidence: 99%

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Valence state, hybridization and electronic band structure in the charge ordered AlV₂O₄

Kalavathi¹,

Amirthapandian²,

Chandra³

et al. 2013

J. Phys.: Condens. Matter

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The valence state, hybridization and electronic band structure of charge ordered AlV2O4 are investigated by measuring the electron energy loss spectra (EELS) and performing band structure calculations using the WIEN2k code. White line ratio and O K edges of V2O5, VO2, V2O3 and AlV2O4, obtained using electron energy loss spectroscopy, are analysed specifically to probe systematically the VO6 octahedra in all of them. The systematic decrease of the L2 intensity and the O K edge intensity from V(5+) in V2O5 to AlV2O4 indicates a progressive increase in the occupancy of the hybridized states, which is corroborated by the absence of a transition from O 1s to hybridized 2t(2g). Band structure calculations on the parent charge frustrated cubic phase and the charge ordered rhombohedral phase clearly document a band gap in the charge ordered state. From the structural information obtained after convergence and the spectroscopic information from EELS, it appears that partial orbital occupancy may lead to a deviation from an integral valence state on all the vanadium in this exotic charge ordered spinel system.

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Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Valence state, hybridization and electronic band structure in the charge ordered AlV₂O₄

Kalavathi¹,

Amirthapandian²,

Chandra³

et al. 2013

J. Phys.: Condens. Matter

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“…Our the differences in the charges between the ions V1, V2 and V3 should be small (see Table 1). A similar conclusion was reached by Prytz et al (2012). Another argument in favor of this conclusion is the proximity of electron density distributions for various V-O bonds in the rhombohedral modification of the AlV 2 O 4 structure (Fig.…”

Section: Crystal Chemistry Of the Alv 2 O 4 Rhombohedral Phasesupporting

confidence: 73%

“…In these works, it was shown that spin-polarization effects should be accounted for in order to reproduce the band structure. Chemical bonding was considered by Prytz et al (2012) using a difference study of electron density and full Bader analysis utilizing planewaves basis set and PBE exchange potential. However, Bader analysis may be inaccurate in the case of metallic bonds (Gatti & Macchi, 2012) with flat regions of electron density which complicates the search of critical points.…”

Section: Density Functional Study Of Charge Distribution and Bondingmentioning

confidence: 99%

Vanadium clusters formation in geometrically frustrated spinel oxide AlV₂O₄

Таланов

Широков

Avakyan

et al. 2018

Acta Crystallogr Sect B

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The spinel oxide AlVO is a unique material, in which the formation of clusters is accompanied by atomic, charge and orbital ordering and a rhombohedral lattice distortion. In this work a theory of the structural phase transition in AlVO is proposed. This theory is based on the study of the order-parameter symmetry, thermodynamics, electron density distribution, crystal chemistry and mechanisms of formation of the atomic and orbital structures of the rhombohedral phase. It is established that the critical order parameter is transformed according to irreducible representation k(τ) (in Kovalev notation) of the Fd \bar{3}m space group. Knowledge of the order-parameter symmetry allows us to show that the derived AlVO rhombohedral structure is a result of displacements of all atom types and the ordering of Al atoms (1:1 order type in tetrahedral spinel sites), V atoms (1:1:6 order type in octahedral sites) and O atoms (1:1:3:3 order type), and the ordering of d, d and d orbitals. Application of the density functional theory showed that V atoms in the Kagomé sublattice formed separate trimers. Also, no sign of metallic bonding between separate vanadium trimers in the heptamer structure was found. The density functional theory study and the crystal chemical analysis of V-O bond lengths allowed us to assume the existence of dimers and trimers as main clusters in the structure of the AlVO rhombohedral modification. The trimer model of the low-symmetry AlVO structure is proposed. Within the Landau theory of phase transitions, typical diagrams of possible phase states are built. It is shown that phase states can be changed as a first-order phase transition close to the second order in the vicinity of tricritical points of the phase diagrams.

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“…The oxidation states of the transition metal oxides to a large extent determine their physiochemical properties. ELNES analysis of the EELS spectrum, with its special valence sensitivity to 3 d transition metals [44,45,46], is capable of revealing the electronic structure of target atoms (i.e., valence state, atomic coordination, and spin state). For instance, making use of the white line ratio ( L 3 / L 2 ) of the Cr- L 2,3 edge, a number of studies have successfully analyzed the oxidation state in chromium oxides [42,43,47].…”

Section: Resultsmentioning

confidence: 99%

ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS

et al. 2019

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The ZnCr2O4/ZnO materials system has a wide range of potential applications, for example, as a photocatalytic material for waste-water treatment and gas sensing. In this study, probe-corrected high-resolution scanning transmission electron microscopy and geometric phase analysis were utilized to study the dislocation structure and strain distribution at the interface between zinc oxide (ZnO) and embedded zinc chromium oxide (ZnCr2O4) particles. Ball-milled and dry-pressed ZnO and chromium oxide (α-Cr2O3) powder formed ZnCr2O4 inclusions in ZnO with size ~400 nm, where the interface properties depended on the interface orientation. In particular, sharp interfaces were observed for ZnO [2113]/ZnCr2O4 [110] orientations, while ZnO [1210]/ZnCr2O4 [112] orientations revealed an interface over several atomic layers, with a high density of dislocations. Further, monochromated electron energy-loss spectroscopy was employed to map the optical band gap of ZnCr2O4 nanoparticles in the ZnO matrix and their interface, where the average band gap of ZnCr2O4 nanoparticles was measured to be 3.84 ± 0.03 eV, in contrast to 3.22 ± 0.01 eV for the ZnO matrix.

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Charge-ordered spinel AlV2O4: High-energy-resolution EELS and computational studies

Cited by 10 publications

References 33 publications

Valence state, hybridization and electronic band structure in the charge ordered AlV₂O₄

Valence state, hybridization and electronic band structure in the charge ordered AlV₂O₄

Vanadium clusters formation in geometrically frustrated spinel oxide AlV₂O₄

ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS

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Charge-ordered spinel AlV2O4: High-energy-resolution EELS and computational studies

Cited by 10 publications

References 33 publications

Valence state, hybridization and electronic band structure in the charge ordered AlV2O4

Valence state, hybridization and electronic band structure in the charge ordered AlV2O4

Vanadium clusters formation in geometrically frustrated spinel oxide AlV2O4

ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS

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Product

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Valence state, hybridization and electronic band structure in the charge ordered AlV₂O₄

Valence state, hybridization and electronic band structure in the charge ordered AlV₂O₄

Vanadium clusters formation in geometrically frustrated spinel oxide AlV₂O₄