scholarly journals Metals in Beta-Rhombohedral Boron

1988 ◽  
Vol 143 ◽  
Author(s):  
Joe Wong ◽  
Glen A. Slack
Keyword(s):  
Solid Solution ◽  
Fine Structure ◽  
Synchrotron Radiation ◽  
Atomic Structure ◽  
Edge Structure ◽  
Coordination Environment ◽  
X Ray ◽  
Metal Diborides ◽  
X Ray Absorption ◽  
Rhombohedral Boron

The bonding and local atomic structure of a series of 3d metal-beta boron solid solution are investigated using a combination of x-ray absorption near-edge structure (XANES) and extended fine structure (EXAFS) technique utilizing intense synchrotron radiation as a light source. The corresponding metal diborides MB2, (M = Sc, Ti, V, Cr).were also measured and used to model the coordination environment of these metal sites in beta-boron.

scholarly journals The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 640 ◽  
Author(s):  
Nikolay D. Trofimov ◽  
Alexander L. Trigub ◽  
Boris R. Tagirov ◽  
Olga N. Filimonova ◽  
Polina V. Evstigneeva ◽  
...  
Keyword(s):  
Solid Solution ◽  
Oxidation State ◽  
Absorption Spectroscopy ◽  
Atomic Structure ◽  
Salt Flux ◽  
Ionic Radii ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Exafs Spectra

The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, and dry synthesis techniques. Oxidation states of dopants were determined using X-ray absorption near edge structure (XANES) technique. The local atomic structure was studied by X-ray absorption fine structure spectroscopy (EXAFS). The spectra were recorded at Zn, In, Ag, and Cu K-edges. In all studied samples, In was in the 3+ oxidation state and replaced Zn in the structure of sphalerite, which occurs with the expansion of the nearest coordination shells due to the large In ionic radius. In the presence of In, the oxidation state of Cu and Ag is 1+, and both metals can form an isomorphous solid solution where they substitute for Zn according to the coupled substitution scheme 2Zn2+ ↔ Me+ + In3+. Moreover, Ag K-edges EXAFS spectra fitting, combined with the results obtained for In- and Au-bearing sphalerite shows that the Me-S distances in the first coordination shell in the solid solution state are correlated with the ionic radii and increase in the order of Cu < Ag < Au. The distortion of the atomic structure increases in the same order. The distant (second and third) coordination shells of Cu and Ag in sphalerite are split into two subshells, and the splitting is more pronounced for Ag. Analysis of the EXAFS spectra, coupled with the results of DFT (Density Function Theory) simulations, showed that the In–In and Me+–In3+ clustering is absent when the metals are present in the sphalerite solid solution. Therefore, all studied admixtures (In, Cu, Ag), as well as Au, are randomly distributed in the matrix of sphalerite, where the concentration of the elements in the “invisible” form can reach a few tens wt.%.

Determination of Bond Lengths and Electronic Structure of Cd1-xZnxTe Ternary Alloys by Synchrotron Radiation

2013 ◽  
Vol 706-708 ◽  
pp. 56-59 ◽  
Author(s):  
Wei Zheng ◽  
Yu Li Wu ◽  
Yen Ting Chen ◽  
Zhe Chuan Feng ◽  
Jyh Fu Lee ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Fine Structure ◽  
Synchrotron Radiation ◽  
Electronic Structures ◽  
Ternary Alloys ◽  
Chemical Bonds ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

High-resolution synchrotron radiation x-ray absorption spectroscopy on Zn K-, Cd L3- and Te L3-edges for Cd1-xZnxTe ternary alloys with x = 0.10, 0.30, 0.50 and 0.90 are presented. A detailed analysis of the extended x-ray absorption fine structure using the IFEFFIT program, and the chemical bonds of Zn-Te are obtained, suggesting distortion of the Te sub-lattice. The x-ray absorption near-edge structure of the Zn K-, Cd L3- and Te L3-edge are investigated, and the electronic structures of Cd1-xZnxTe with various compositions are studied.

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.

Fluorescence Extended X-Ray Absorption Fine Structure Study on Local Structures of Rare-Earth-Doped InGaGdN

2016 ◽  
Vol 1133 ◽  
pp. 429-433
Author(s):  
Siti Nooraya Mohd Tawil ◽  
Shuichi Emura ◽  
Daivasigamani Krishnamurthy ◽  
Hajime Asahi
Keyword(s):  
Fine Structure ◽  
Rare Earth ◽  
Nearest Neighbor ◽  
Structure Study ◽  
Edge Structure ◽  
X Ray ◽  
Local Structures ◽  
Absorption Fine ◽  
X Ray Absorption

Local structures around gadolinium atoms in rare-earth (RE)-doped InGaGdN thin films were studied by means of fluorescence extended X-ray absorption fine structure (EXAFS) measured at the Gd LIII-edges. The samples were doped with Gd in-situ during growth by plasma-assisted molecular beam epitaxy (PAMBE). Gd LIII-edge EXAFS signal from the GaGdN, GdN and Gd foil were also measured as reference. The X-ray absorption near edge structure (XANES) spectra around Gd LIII absorption edge of InGaGdN samples observed at room temperature indicated the enhancement of intensities with the increase of Gd composition. Further EXAFS analysis inferred that the Gd atoms in InGaN were surrounded by similar atomic shells as in the case of GaGdN with the evidence indicating majority of Gd atoms substituted into Ga sites of InGaGdN. A slight elongation of bond length for the 2nd nearest-neighbor (Gd–Ga) of sample with higher Gd concentration was also observed.

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