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.

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.

scholarly journals Solving local structure around dopants in metal nanoparticles with ab initio modeling of X-ray absorption near edge structure

2016 ◽  
Vol 18 (29) ◽  
pp. 19621-19630 ◽  
Author(s):  
Janis Timoshenko ◽  
Atal Shivhare ◽  
Robert W. J. Scott ◽  
Deyu Lu ◽  
Anatoly I. Frenkel
Keyword(s):  
Ab Initio ◽  
Metal Nanoparticles ◽  
Local Structure ◽  
Heterogeneous Catalysts ◽  
Edge Structure ◽  
X Ray ◽  
Metal Impurities ◽  
Local Environments ◽  
X Ray Absorption ◽  
Xanes Analysis

XANES analysis guided by ab initio modeling is proposed for refinement of local environments around metal impurities in heterogeneous catalysts.

scholarly journals Neural network assisted analysis of bimetallic nanocatalysts using X-ray absorption near edge structure spectroscopy

2020 ◽  
Vol 22 (34) ◽  
pp. 18902-18910 ◽  
Author(s):  
Nicholas Marcella ◽  
Yang Liu ◽  
Janis Timoshenko ◽  
Erjia Guan ◽  
Mathilde Luneau ◽  
...  
Keyword(s):  
Neural Network ◽  
Local Structure ◽  
Bimetallic Nanoparticles ◽  
Edge Structure ◽  
X Ray ◽  
Coordination Numbers ◽  
Rich Information ◽  
Bimetallic Nanocatalysts ◽  
Assisted Analysis ◽  
X Ray Absorption

Trained neural networks are used to extract the first partial coordination numbers from XANES spectra. In bimetallic nanoparticles, the four local structure descriptors provide rich information on structural motifs.

Local Structure of Pr, Nd, and Sm Complex Oxides and Their X-ray Absorption Near Edge Structure Spectra

2014 ◽  
Vol 118 (36) ◽  
pp. 20881-20888 ◽  
Author(s):  
Hiroyuki Asakura ◽  
Tetsuya Shishido ◽  
Shingo Fuchi ◽  
Kentaro Teramura ◽  
Tsunehiro Tanaka
Keyword(s):  
Local Structure ◽  
Complex Oxides ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

X-Ray Absorption Study of Y1Ba2Cu3O7 and Gd1Ba2Cu3O7 Superconductors

1987 ◽  
Vol 99 ◽  
Author(s):  
J. B. Boyce ◽  
F. Bridges ◽  
T. Claeson ◽  
R. S. Howland ◽  
T. H. Geballe
Keyword(s):  
Diffraction Data ◽  
Local Structure ◽  
Absorption Study ◽  
X Ray ◽  
Significant Difference ◽  
Atomic Vibrations ◽  
Einstein Temperature ◽  
X Ray Absorption ◽  
Absorption Measurements

ABSTRACTX-ray absorption measurements of the high-Tc superconductors Y1Ba2Cu3O7-δ and Gd1Ba2Cu3O7-δ are essentially identical and show no significant difference in either near-edge or local structure from 4.2K to 688K. The position of the Cu edge suggests that the Cu valence in the superconductors is between that in CuO (formal valence of II) and that in KCuO2 (formal valence of III). Our EXAFS structural results agree well with the diffraction data. From the atomic vibrations, we find that the 2D Cu-O planes and the ID Cu-O chains form the most rigid parts of the structure, with an Einstein temperature of about 560K, compared with 390K for the Y-O bonds, 320K for Ba-O, and 260K for Cu-Cu and Y-Cu.

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