Asymmetric effects in the extended X-ray absorption fine structure analysis of solid and liquid zinc

1980 ◽  
Vol 58 (9) ◽  
pp. 1388-1399 ◽  
Author(s):  
E. D. Crozier ◽  
A. J. Seary
Keyword(s):  
Fine Structure ◽  
Liquid Metals ◽  
Distribution Functions ◽  
Asymmetric Distribution ◽  
Nearest Neighbour ◽  
Exafs Data ◽  
X Ray ◽  
Asymmetric Effects ◽  
Absorption Fine ◽  
X Ray Absorption

Extended X-ray absorption fine structure (EXAFS) results are presented for solid and liquid Zn for the temperature range 273 to 782 K. At the higher temperatures the distribution of nearest neighbour atoms is asymmetric. Neglect of the asymmetry and use of EXAFS analysis methods developed for symmetric distribution functions gives an underestimate of the nearest neighbour distance R1 and the disorder parameter σ12. It is shown that a transform analysis can be useful in detecting asymmetric effects, and methods of analyzing the EXAFS of asymmetric distributions are presented. An anharmonic oscillator model is applied to the EXAFS data of polycrystalline Zn to correct the values of R1 and σ12. The corrected values of σ12 are found to be~20% higher than those predicted by a Debye model. An empirical, analytically simple asymmetric distribution function is fitted to the liquid data to obtain promising agreement with the nearest neighbour structure as deduced from X-ray diffraction studies. Finally it is shown by applying the Blip-function model of liquid metals that, in principle, the large k-range spanned by EXAFS data can be used to specify the repulsive portion of the ion–ion interaction potential of liquid metals.

scholarly journals Nearest-neighbour distribution of distances in crystals from extended X-ray absorption fine structure

2017 ◽  
Vol 147 (4) ◽  
pp. 044503 ◽  
Author(s):  
P. Fornasini ◽  
R. Grisenti ◽  
M. Dapiaggi ◽  
G. Agostini ◽  
T. Miyanaga
Keyword(s):  
Fine Structure ◽  
Nearest Neighbour ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

Structural determinations of liquid semiconductors using extended X-ray absorption fine structure

1977 ◽  
Vol 55 (11) ◽  
pp. 1968-1974 ◽  
Author(s):  
E. D. Crozier ◽  
F. W. Lytle ◽  
D. E. Sayers ◽  
E. A. Stern
Keyword(s):  
Fine Structure ◽  
Disordered Systems ◽  
Structural Changes ◽  
Structural Information ◽  
Structural Rearrangement ◽  
Nearest Neighbour ◽  
X Ray ◽  
Absorption Fine ◽  
Amorphous States ◽  
X Ray Absorption

The extended fine structure in the X-ray absorption coefficient is dominated by the interference of the photoelectron scattered by atoms in the immediate neighbourhood of the atom which absorbs the X-ray photon and thus can provide structural information about ordered or disordered systems. In this paper it is demonstrated that Extended X-Ray Absorption Fine Structure (EXAFS) measurements can be made on liquid systems at high temperatures. The technique is illustrated with results for As2Se3 in the liquid and amorphous states for temperatures between 100 and 773 K. A Fourier analysis of the EXAFS data reveals that a major structural rearrangement does not occur in the nearest neighbour shell when As2Se3 is melted. However, small structural changes do occur at the melting point which, within the limitations of the present data, suggest a slight increase in the nearest neighbour As–Se distance, a decrease in the number of nearest neighbours, and a decrease in the nearest neighbour disorder term σ12.

scholarly journals Analysis of extended X-ray absorption fine structure (EXAFS) data using artificial intelligence techniques

2021 ◽  
Vol 547 ◽  
pp. 149059
Author(s):  
Jeff Terry ◽  
Miu Lun Lau ◽  
Jiateng Sun ◽  
Chang Xu ◽  
Bryan Hendricks ◽  
...  
Keyword(s):  
Artificial Intelligence ◽  
Fine Structure ◽  
Exafs Data ◽  
X Ray ◽  
Artificial Intelligence Techniques ◽  
Absorption Fine ◽  
X Ray Absorption

scholarly journals A combined fit of total scattering and extended X-ray absorption fine structure data for local-structure determination in crystalline materials

2009 ◽  
Vol 42 (5) ◽  
pp. 867-877 ◽  
Author(s):  
V. Krayzman ◽  
I. Levin ◽  
J. C. Woicik ◽  
Th. Proffen ◽  
T. A. Vanderah ◽  
...  
Keyword(s):  
Fine Structure ◽  
Multiple Scattering ◽  
Structure Determination ◽  
Local Structure ◽  
Group Symmetry ◽  
Total Scattering ◽  
Exafs Data ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

Reverse Monte Carlo (RMC) refinements of local structure using a simultaneous fit of X-ray/neutron total scattering and extended X-ray absorption fine structure (EXAFS) data were developed to incorporate an explicit treatment of both single- and multiple-scattering contributions to EXAFS. The refinement algorithm, implemented as an extension to the public domain computer softwareRMCProfile, enables accurate modeling of EXAFS over distances encompassing several coordination shells around the absorbing species. The approach was first tested on Ni, which exhibits extensive multiple scattering in EXAFS, and then applied to perovskite-like SrAl1/2Nb1/2O3. This compound crystallizes with a cubic double-perovskite structure but presents a challenge for local-structure determination using a total pair-distribution function (PDF) alone because of overlapping peaks of the constituent partial PDFs (e.g.Al—O and Nb—O or Sr—O and O—O). The results obtained here suggest that the combined use of the total scattering and EXAFS data provides sufficient constraints for RMC refinements to recover fine details of local structure in complex perovskites. Among other results, it was found that the probability density distribution for Sr in SrAl1/2Nb1/2O3adoptsTdpoint-group symmetry for the Sr sites, determined by the ordered arrangement of Al and Nb, as opposed to a spherical distribution commonly assumed in traditional Rietveld refinements.

scholarly journals Study on crystallographic and electronic structure of micrometre-scale ZnO and ZnO:B rods via X-ray absorption fine-structure spectroscopy

2021 ◽  
Vol 28 (2) ◽  
pp. 448-454
Author(s):  
Selma Erat ◽  
Osman Murat Ozkendir ◽  
Saadet Yildirimcan ◽  
Selen Gunaydin ◽  
Messaoud Harfouche ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electronic Structure ◽  
Fine Structure ◽  
Crystallographic Analysis ◽  
Crystallographic Structure ◽  
Edge Structure ◽  
Exafs Data ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectra were recorded to investigate the electronic structure and local crystal structure of ZnO and ZnO:B powders produced via hydrothermal synthesis. ZnO and ZnO:B grow as micrometre-scale rods with hexagonal shape, as confirmed by scanning electron microscopy micrographs. The number of broken ZnO:B rods increases with increasing B concentration, as observed in the images, due to B atoms locating in between the Zn and O atoms which weakens and/or breaks the Zn–O bonds. However, no disorder within the crystallographic structure of ZnO upon B doping is observed from X-ray diffraction results, which were supported by EXAFS results. To determine the atomic locations of boron atoms in the crystal structure and their influence on the zinc atoms, EXAFS data were fitted with calculated spectra using the crystal structure parameters obtained from the crystallographic analysis of the samples. EXAFS data fitting and complementary k-weight analysis revealed the positions of the B atoms – their positions were determined to be in between the Zn and O atoms.

Understanding Degradation of Doped Electroluminescent ZnS Phosphors

2008 ◽  
Vol 1083 ◽  
Author(s):  
Yu Jiang ◽  
Jacob Stanley ◽  
Laurel Ruhlen ◽  
Chris France ◽  
John Willey ◽  
...  
Keyword(s):  
Fine Structure ◽  
Atomic Structure ◽  
Local Atomic Structure ◽  
Exafs Data ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption ◽  
Zns Phosphors

ABSTRACTWe have shown recently that the degradation of AC electroluminescence (EL) in ZnS:Cu,Cl and similar phosphors can be significantly reversed by a short anneal near 200°C. To better understand the degradation/rejuvenation processes, we investigated EL degradation and rejuvenation under different conditions. To probe for changes in the local atomic structure about the Cu sites, we collected Extended X-ray Absorption Fine Structure (EXAFS) data at the Cu K-edge EXAFS data for several as-made, thermally degraded (240°C anneal), and EL degraded powders.

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