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.

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.

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.

Study on Effects of Heavy Ion Irradiation on CeO2 by Using Synchrotron Radiation X-Ray Absorption Spectroscopy -as a Simulation Study for Radiation Damage in High-Burnup Light Water Reactor Fuels-

2007 ◽  
Vol 1043 ◽  
Author(s):  
Hirotaka Ohno ◽  
Daiju Matsumura ◽  
Yasuo Nishihata ◽  
Jun'ichiro Mizuki ◽  
Norito Ishikawa ◽  
...  
Keyword(s):  
Thin Films ◽  
Synchrotron Radiation ◽  
Ion Irradiation ◽  
Heavy Ion ◽  
Waller Factor ◽  
X Ray ◽  
Debye Waller Factor ◽  
Atomic Distance ◽  
Exafs Measurement ◽  
X Ray Absorption

AbstractCeO2 thin films were irradiated with 200MeV Xe ions. Effects of the irradiation were studied by using Extended X-ray Absorption Fine Structure (EXAFS) measurement at SPring8 synchrotron radiation facility. EXAFS spectra for the irradiated thin films near the Ce K-edge show that the coordination number for oxygen atoms around Ce atom decreases and that the Ce-O Debye-Waller factor increases by the irradiation. The atomic distance between oxygen atom and Ce atom does not vary within the accuracy of EXAFS measurement. The effect of high density electronic excitation on the structure of CeO2 is discussed.

ISOTOPIC EFFECT IN DEBYE–WALLER FACTOR OF CRYSTALLINE GERMANIUM

2013 ◽  
Vol 27 (26) ◽  
pp. 1350191
Author(s):  
HO KHAC HIEU ◽  
VU VAN HUNG
Keyword(s):  
Lattice Dynamics ◽  
Mass Difference ◽  
Relative Displacement ◽  
Waller Factor ◽  
Isotopic Effect ◽  
Mean Square ◽  
X Ray ◽  
Debye Waller Factor ◽  
X Ray Absorption ◽  
Crystalline Germanium

The statistical moment method has been used to study the effect of isotopic mass difference on extended X-ray absorption fine structure (EXAFS) Debye–Waller factor of crystalline germanium. The effects on the parallel mean-square relative displacement and the atomic mean square displacements have been considered. This research also exposed that isotopic effect is noticeable where the correlated atomic motion is concerned. Numerical calculations have been performed for two isotopes 70 Ge and 76 Ge in range of temperature from 0 K to 600 K. Our results are compared with available experimental EXAFS data [J. Purans et al., Phys. Rev. Lett.100 (2008) 055901] as well as with lattice dynamics calculations [A. Sanson, Solid State Sci.12 (2010) 1988] and the good agreements are found.

Evolution of the Nanostructure of Giant Magnetoresistance Heterogeneous Alloys CoxAg1-x Upon Annealing

1995 ◽  
Vol 400 ◽  
Author(s):  
J. R. Regnard ◽  
C. Revenant-Brizard ◽  
B. Dieny ◽  
B. Mevel ◽  
J. Mimault
Keyword(s):  
Giant Magnetoresistance ◽  
Annealing Temperature ◽  
Liquid Nitrogen Temperature ◽  
Waller Factor ◽  
Total Electron Yield ◽  
Total Electron ◽  
X Ray ◽  
Debye Waller Factor ◽  
X Ray Absorption ◽  
Heterogeneous Alloys

AbstractHeterogeneous alloys CoxAg1-x with atomic concentrations x=0.20 and 0.35, presenting giant magnetoresistance properties, have been studied by Total Electron Yield X-ray absorption spectroscopy at liquid nitrogen temperature at the Co K edge after annealings at various temperatures. For both sample concentrations, the Co atoms are mainly in small filament agglomerates for the as-deposited and low temperature annealed samples (T<150°C). In this temperature range, the local Co atomic environment is very stable and disordered. A structural change has been detected by XANES and EXAFS analysis between the 250 and 400°C annealings. After a 400°C annealing during 10 min, the nanostructures evolve towards larger, more compact and well ordered granules. The Co-Co distance varies from 0.246 to 0.248 nm as the annealing temperature increases indicating that the small filament-shaped agglomerates are under strain in the Ag matrix. The Debye-Waller factor of the Co0.35Ag0.65 samples decreases continously as the annealing temperature increases, as this factor drops suddenly after a 250°C annealing for the Co0.20Ag0.80 sample. The Co agglomeration is steadily larger for the Co0.35Ag0.65 sample than for the Co0.20Ag0.80 one. The Co-Ag contribution is negligible for the Co0.35Ag0.65 sample, as it represents approximately one third of the nearest neighbors for the Co0.20Ag0.80 sample from the as-deposit up to a 250°C annealing stage.

X-ray absorption of bromonaphthalene dissolved in supercritical fluid xenon

1998 ◽  
Vol 5 (3) ◽  
pp. 1004-1006 ◽  
Author(s):  
T. Murata ◽  
K. Nakagawa ◽  
Y. Otsuki ◽  
I. Shimoyama ◽  
T. Mizutani ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Supercritical Fluid ◽  
Large Degree ◽  
Waller Factor ◽  
Pure Liquid ◽  
High Pressure Cell ◽  
X Ray ◽  
Debye Waller Factor ◽  
X Ray Absorption ◽  
Best Fit

The results of Br K-edge X-ray absorption measurements of 1-bromonaphthalene dissolved in supercritical fluid Xe are reported. As the pressure of Xe confined in a high-pressure cell is increased, the absorption spectrum of bromonaphthalene gradually appears, showing that Xe in the supercritical fluid state solvates the bromonaphthalene molecule. The spectrum of the dissolved sample shows a remarkable difference from that of the pure liquid sample in the near-edge region of the X-ray absorption spectrum, reflecting the interaction of the solute material with solvent Xe. Ab initio full multiple-scattering calculations can reproduce the spectral features qualitatively. A large value of the Debye–Waller factor must be introduced to give the best fit, corresponding to a large degree of spatial disorder and violent thermal vibration of the Xe atoms around the Br atom.

Tracking of arsenics during the thermal stabilization of an AsH3 scrubber sludge

2013 ◽  
Vol 68 (9) ◽  
pp. 2007-2011 ◽  
Author(s):  
Chang-Yu Liao ◽  
Fang-Chih Chang ◽  
H. Paul Wang ◽  
Yu-Ling Wei ◽  
Chih-Ju G. Jou
Keyword(s):  
Fine Structure ◽  
High Temperature ◽  
Thermal Stabilization ◽  
Bonding Energy ◽  
Edge Structure ◽  
X Ray ◽  
Temperature Range ◽  
Absorption Fine ◽  
X Ray Absorption ◽  
Exafs Spectra

Toxic arsenics in an AsH3 scrubber sludge were thermally stabilized in the temperature range of 973–1,373 K. To better understand how the high-temperature treatments can stabilize arsenics in the sludge, their synchrotron X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra of arsenics were determined. It is found that the reduced arsenic leachability may be associated with the formation of As2O5 (51–59%) and embedded As(V) within the Ca3(PO4)2 matrix (41–49%) in the stabilized sludge. In addition, the As-O bond distances in the stabilized As2O5 are much less than that of normal As2O5 by 0.05–0.07 Å. The shorter As-O bond distances accompanied with the higher bonding energy also have a contribution to the thermal stabilization of arsenics.

Sign in / Sign up

Export Citation Format

Share Document