X-ray absorption near edge structures in cobalt oxides

1996 ◽  
Vol 11 (9) ◽  
pp. 2242-2256 ◽  
Author(s):  
T. Jiang ◽  
D. E. Ellis
Keyword(s):  
Wave Functions ◽  
Site Symmetry ◽  
Local Geometry ◽  
Final State ◽  
Cluster Technique ◽  
Edge Structure ◽  
X Ray ◽  
Local Electronic Structure ◽  
Edge Features ◽  
X Ray Absorption

Theoretical studies have been made of K-edge x-ray absorption near edge structure (XANES) of Co in CoO, Co(OH)2, CoTiO3, Co3O4, and CoAl2O4. Correlations of experimental near edge features with site symmetry, local geometry, local electronic structure, i.e., atomic configuration, charge transfer, and backscattering from neighboring atomic potentials are interpreted. The self-consistent Discrete Variational Xa Method (DV-Xα) within an embedded cluster technique has been used to generate the crystal potential. A multiple scattering (MS) approach is then used to solve for the final state wave function. The ground state DV wave functions are analyzed in terms of the projected density of states, whereas the final state MS continuum wave functions are analyzed through the concept of photoelectron trapping time.

Extended X-ray absorption fine structure and multiple-scattering simulation of nickel dithiolene complexes Ni[S2C2(CF3)2]2n(n= −2, −1, 0) and an olefin adduct Ni[S2C2(CF3)2]2(1-hexene)

2015 ◽  
Vol 22 (1) ◽  
pp. 124-129 ◽  
Author(s):  
Weiwei Gu ◽  
Hongxin Wang ◽  
Kun Wang
Keyword(s):  
Fine Structure ◽  
Multiple Scattering ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
Square Planar ◽  
Square Planar Complexes ◽  
Uv Visible ◽  
Edge Features ◽  
X Ray Absorption

A series of Ni dithiolene complexes Ni[S2C2(CF3)]2n(n= −2, −1, 0) (1,2,3) and a 1-hexene adduct Ni[S2C2(CF3)2]2(C6H12) (4) have been examined by NiK-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectroscopies. Ni XANES for1–3reveals clear pre-edge features and approximately +0.7 eV shift in the NiK-edge position for `one-electron' oxidation. EXAFS simulation shows that the Ni—S bond distances for1,2and3(2.11–2.16 Å) are within the typical values for square planar complexes and decrease by ∼0.022 Å for each `one-electron' oxidation. The changes in NiK-edge energy positions and Ni—S distances are consistent with the `non-innocent' character of the dithiolene ligand. The Ni—C interactions at ∼3.0 Å are analyzed and the multiple-scattering parameters are also determined, leading to a better simulation for the overall EXAFS spectra. The 1-hexene adduct4presents no pre-edge feature, and its NiK-edge position shifts by −0.8 eV in comparison with its starting dithiolene complex3. Consistently, EXAFS also showed that the Ni—S distances in4elongate by ∼0.046 Å in comparison with3. The evidence confirms that the neutral complex is `reduced' upon addition of olefin, presumably by olefin donating the π-electron density to the LUMO of3as suggested by UV/visible spectroscopy in the literature.

Local electronic structure of ZnS and ZnSe doped by Mn, Fe, Co, and Ni from x-ray-absorption near-edge structure studies

1996 ◽  
Vol 53 (3) ◽  
pp. 1119-1128 ◽  
Author(s):  
K. L/awniczak-Jabl/onska ◽  
R. J. Iwanowski ◽  
Z. Gol/acki ◽  
A. Traverse ◽  
S. Pizzini ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Edge Structure ◽  
X Ray ◽  
Local Electronic Structure ◽  
X Ray Absorption

Temperature dependence of pre-edge features in TiK-edge XANES spectra forATiO3(A= Ca and Sr),A2TiO4(A= Mg and Fe), TiO2rutile and TiO2anatase

2013 ◽  
Vol 20 (4) ◽  
pp. 641-643 ◽  
Author(s):  
Tatsuya Hiratoko ◽  
Akira Yoshiasa ◽  
Tomotaka Nakatani ◽  
Maki Okube ◽  
Akihiko Nakatsuka ◽  
...  
Keyword(s):  
Invariant Point ◽  
Waller Factor ◽  
Edge Structure ◽  
X Ray ◽  
Temperature Range ◽  
Peak Intensity ◽  
Debye Waller Factor ◽  
Edge Features ◽  
X Ray Absorption ◽  
Titanium Compounds

XANES (X-ray absorption near-edge structure) spectra of the TiK-edges ofATiO3(A= Ca and Sr),A2TiO4(A= Mg and Fe), TiO2rutile and TiO2anatase were measured in the temperature range 20–900 K. Ti atoms for all samples were located in TiO6octahedral sites. The absorption intensity invariant point (AIIP) was found to be between the pre-edge and post-edge. After the AIIP, amplitudes damped due to Debye–Waller factor effects with temperature. Amplitudes in the pre-edge region increased with temperature normally by thermal vibration. Use of the AIIP peak intensity as a standard point enables a quantitative comparison of the intensity of the pre-edge peaks in various titanium compounds over a wide temperature range.

Investigation of Sulfur Crosslinking Interfacial of Natural Rubber (NR) Blending with Carboxyalted Styrene Butadiene Rubber (XSBR) Using X-Ray Absorption Spectroscopy

2015 ◽  
Vol 1087 ◽  
pp. 131-136
Author(s):  
Chanaphan Lamlong ◽  
Wirach Taweepreda ◽  
Rattapong Nu-Mard ◽  
Prayoon Songsiriritthigul
Keyword(s):  
Natural Rubber ◽  
Crosslinking Density ◽  
Styrene Butadiene Rubber ◽  
Local Geometry ◽  
Butadiene Rubber ◽  
Edge Structure ◽  
X Ray ◽  
Oxidative Processes ◽  
Styrene Butadiene ◽  
X Ray Absorption

The sulfur crosslinking films from Natural Rubber (NR), Carboxylated Stryrene Butadiene Rubber (XSBR) latices, and their blends have been investigated using X-ray absorption near-edge structure spectroscopy (XANES). The film was prepared by casting the latex compound on glass surface and heating at 120oC in a hot air oven for 10 minutes. The sulfur crosslinking density were studied by the XANES. This was done to provide the local geometry and electronic environment of sulfur bonding in the rubber networks. We found that the reversion takes place before the onset of oxidative processes at the sulfur bridges. Parallel to the oxidative processes, the production of cyclic sulfanes takes places. This relationship depends on the rubber compositions.

Titanium coordination in silicate glasses investigated using O K-edge X-ray absorption spectroscopy

2003 ◽  
Vol 67 (4) ◽  
pp. 597-607 ◽  
Author(s):  
G. S. Henderson ◽  
Xiaoyang Liu ◽  
M. E. Fleet
Keyword(s):  
Glass Sample ◽  
Surface Region ◽  
Bulk Sample ◽  
Silicate Glasses ◽  
Titanium Silicate ◽  
Edge Structure ◽  
Near Surface ◽  
X Ray ◽  
Edge Features ◽  
X Ray Absorption

AbstractA series of titanium silicate glasses along the composition joins TiO2-SiO2, TiO2-Na2SiO3, TiO2-K2SiO3 and TiO2-CaSiO3, has been examined using oxygen K-edge X-ray absorption near edge structure spectroscopy (XANES) confined to the near-surface region. Sharp pre-edge features in the spectra can be used to determine the Ti coordination in the glasses. The presence of [4]Ti is indicated by a pre-edge peak at ∼534 eV while [5]Ti is indicated by a peak at ∼533 eV. Titanium exists in all these glasses as [4]Ti and [5]Ti with no [6]Ti being present. For alkali-containing glasses the [5]Ti site becomes more prevalent with increasing TiO2. TiO2-K2SiO3 compositions contain a greater proportion of [4]Ti than comparable Na2O compositions. This is consistent with earlier Ti L-edge findings. The TEY spectra for the TiO2-CaSiO3 compositions indicate the presence of significant amounts of [5]Ti at high TiO2 contents; however, comparison of TEY (near surface) and FY (bulk sample) XANES shows that the [5]Ti is confined to the surface of the glass sample with the bulk of the glass containing [4]Ti.

Interplay between Local Electronic Structure, Crystalline Structure and Magnetic Ordering in Intermetallic Compounds Ce2Fe17−xMnx

2012 ◽  
Vol 190 ◽  
pp. 251-254 ◽  
Author(s):  
Alexander A. Yaroslavtsev ◽  
Alexey P. Menushenkov ◽  
Olga V. Grishina ◽  
Roman V. Chernikov ◽  
Anatoly G. Kuchin
Keyword(s):  
Crystalline Structure ◽  
Magnetic Ordering ◽  
Local Environment ◽  
Edge Structure ◽  
X Ray ◽  
Local Electronic Structure ◽  
Magnetic States ◽  
First Time ◽  
X Ray Absorption ◽  
Mn Concentration

For the first time the rearrangement of cerium local environment in Ce2Fe17-xMnx(x = 0; 1; 2) intermetallics vs. Mn concentration and temperature was investigated by thespectroscopy of extended X-ray absorption fine structure (EXAFS) above K-Ce absorptionedge. At the same time under similar conditions by the spectroscopy of X-ray absorption near-edge structure (XANES) above L3-Ce absorption edge the valence state of Ce was studied. Thecorrelation is found between changes in local electronic and crystalline structure observed inCe2Fe17-xMnx and the types of magnetic states in these compounds.

scholarly journals The Local Structure of the BiS2 Layer in RE(O,F)BiS2 Determined by In-Plane Polarized X-ray Absorption Measurements

Physchem ◽  
2021 ◽  
Vol 1 (3) ◽  
pp. 250-258
Author(s):  
G. M. Pugliese ◽  
L. Tortora ◽  
E. Paris ◽  
T. Wakita ◽  
K. Terashima ◽  
...  
Keyword(s):  
Local Structure ◽  
Spectral Weight ◽  
Local Geometry ◽  
Edge Structure ◽  
X Ray ◽  
Quantitative Measurements ◽  
Spacer Layer ◽  
Weight Transfer ◽  
X Ray Absorption ◽  
Absorption Measurements

We have investigated the local structure of BiS2-based layered materials by Bi L3-edge extended X-ray absorption fine structure (EXAFS) measurements performed on single crystal samples with polarization of the X-ray beam parallel to the BiS2 plane. The results confirm highly instable nature of BiS2 layer, characterized by ferroelectric like distortions. The distortion amplitude, determined by the separation between the two in-plane (Bi-S1) bonds, is found to be highest in LaO0.77F0.23BiS2 with ΔR∼0.26 Å and lowest in NdO0.71F0.29BiS2 with ΔR∼0.13 Å. Among the systems with intrinsic doping, CeOBiS2 shows smaller distortion (ΔR∼0.15 Å) than PrOBiS2 (ΔR∼0.18 Å) while the highest distortion appears for EuFBiS2 revealing ΔR∼0.22 Å. It appears that the distortion amplitude is controlled by the nature of the RE(O,F) spacer layer in the RE(O,F)BiS2 structure. The X-ray absorption near edge structure (XANES) spectra, probing the local geometry, shows a spectral weight transfer that evolves systematically with the distortion amplitude in the BiS2-layer. The results provide a quantitative measurements of the local distortions in the instable BiS2-layer with direct implication on the physical properties of these materials.

Experimental investigation of FeCO3 (siderite) stability in Earth's lower mantle using XANES spectroscopy

2019 ◽  
Vol 104 (8) ◽  
pp. 1083-1091 ◽  
Author(s):  
Valerio Cerantola ◽  
Max Wilke ◽  
Innokenty Kantor ◽  
Leyla Ismailova ◽  
Ilya Kupenko ◽  
...  
Keyword(s):  
High Spin ◽  
Lower Mantle ◽  
Spin Crossover ◽  
High Spin State ◽  
Xanes Spectroscopy ◽  
Edge Structure ◽  
X Ray ◽  
Edge Features ◽  
The Stability ◽  
X Ray Absorption

Abstract We studied FeCO3 using Fe K-edge X-ray absorption near-edge structure (XANES) spectroscopy at pressures up to 54 GPa and temperatures above 2000 K. First-principles calculations of Fe at the K-edge in FeCO3 were performed to support the interpretation of the XANES spectra. The variation of iron absorption edge features with pressure and temperature in FeCO3 matches well with recently reported observations on FeCO3 at extreme conditions, and provides new insight into the stability of Fe-carbonates in Earth's mantle. Here we show that at conditions of the mid-lower mantle, ~50 GPa and ~2200 K, FeCO3 melts and partially decomposes to high-pressure Fe3O4. Carbon (diamond) and oxygen are also inferred products of the reaction. We constrained the thermodynamic phase boundary between crystalline FeCO3 and melt to be at 51(1) GPa and ~1850 K. We observe that at 54(1) GPa, temperature-induced spin crossover of Fe2+ takes place from low to high spin such that at 1735(100) K, all iron in FeCO3 is in the high-spin state. A comparison between experiment and theory provides a more detailed understanding of FeCO3 decomposition observed in X-ray absorption spectra and helps to explain spectral changes due to pressure-induced spin crossover in FeCO3 at ambient temperature.

Chemical and orientational imaging of polymeric samples

1994 ◽  
Vol 52 ◽  
pp. 68-69
Author(s):  
H. Ade ◽  
B. Hsiao ◽  
G. Mitchell ◽  
E. Rightor ◽  
A. P. Smith ◽  
...  
Keyword(s):  
Ethylene Terephthalate ◽  
National Laboratory ◽  
Brookhaven National Laboratory ◽  
Carbonyl Groups ◽  
Aromatic Rings ◽  
Edge Structure ◽  
X Ray ◽  
Scanning Transmission ◽  
Polymeric Samples ◽  
X Ray Absorption

We have used the Scanning Transmission X-ray Microscope at beamline X1A (X1-STXM) at Brookhaven National Laboratory (BNL) to acquire high resolution, chemical and orientation sensitive images of polymeric samples as well as point spectra from 0.1 μm areas. This sensitivity is achieved by exploiting the X-ray Absorption Near Edge Structure (XANES) of the carbon K edge. One of the most illustrative example of the chemical sensitivity achievable is provided by images of a polycarbonate/pol(ethylene terephthalate) (70/30 PC/PET) blend. Contrast reversal at high overall contrast is observed between images acquired at 285.36 and 285.69 eV (Fig. 1). Contrast in these images is achieved by exploring subtle differences between resonances associated with the π bonds (sp hybridization) of the aromatic groups of each polymer. PET has a split peak associated with these aromatic groups, due to the proximity of its carbonyl groups to its aromatic rings, whereas PC has only a single peak.

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