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

Probing the Local Atomic Structure of In and Cu in Sphalerite by XAS Spectroscopy Enhanced by Reverse Monte Carlo Algorithm

1
National Research Centre ‘Kurchatov Institute’, 1 Akademika Kurchatova pl., 123182 Moscow, Russia
2
Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia
3
Institute of Geology of Ore Deposits (IGEM RAS), 35, Staromonetnyi per., 119017 Moscow, Russia
4
The Rossendorf Beamline at ESRF—The European Synchrotron, CS40220, 38043 Grenoble CEDEX 9, France
5
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden, Germany
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(10), 841; https://doi.org/10.3390/min10100841
Received: 10 July 2020 / Revised: 21 September 2020 / Accepted: 22 September 2020 / Published: 24 September 2020
(This article belongs to the Special Issue X-ray Absorption Spectroscopy of Synthetic and Natural Minerals)
The distortion of atomic structure around In and Cu dopants in sphalerite ZnS was explored by extended X-ray absorption fine structure (EXAFS) spectroscopy enhanced by reverse Monte Carlo (RMC) simulation (RMC-EXAFS method). These data were complemented with quantum chemical Density Functional Theory (DFT) calculations and theoretical modeling of X-ray absorption near edge spectroscopy (XANES) spectra. The RMC-EXAFS method showed that in the absence of Cu, the In-bearing solid solution is formed via the charge compensation scheme 3Zn2+↔2In3+ + □, where □ is a Zn vacancy. The coordination spheres of In remain undistorted. Formation of the solid solution in the case of (In, Cu)-bearing sphalerites follows the charge compensation scheme 2Zn2+↔Cu+ + In3+. In the solid solution, splitting of the interatomic distances in the 2nd and 3rd coordination spheres of In and Cu is observed. The dopants’ local atomic structure is slightly distorted around In but highly distorted around Cu. The DFT calculations showed that the geometries with close arrangement (clustering) of the impurities—In and Cu atoms, or the In atom and a vacancy—are energetically more favorable than the random distribution of the defects. However, as no heavy In atoms were detected in the 2nd shell of Cu by means of EXAFS, and the 2nd shell of In was only slightly distorted, we conclude that the defects are distributed randomly (or at least, not close to each other). The disagreement of the RMC-EXAFS fittings with the results of the DFT calculations, according to which the closest arrangement of dopants is the most stable configuration, can be explained by the presence of other defects of the sphalerite crystal lattice, which were not considered in the DFT calculations. View Full-Text
Keywords: sphalerite; synthetic minerals; X-ray absorption spectroscopy; EXAFS; XANES; indium; copper; trace elements; impurities sphalerite; synthetic minerals; X-ray absorption spectroscopy; EXAFS; XANES; indium; copper; trace elements; impurities
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MDPI and ACS Style

Trigub, A.L.; Trofimov, N.D.; Tagirov, B.R.; Nickolsky, M.S.; Kvashnina, K.O. Probing the Local Atomic Structure of In and Cu in Sphalerite by XAS Spectroscopy Enhanced by Reverse Monte Carlo Algorithm. Minerals 2020, 10, 841. https://doi.org/10.3390/min10100841

AMA Style

Trigub AL, Trofimov ND, Tagirov BR, Nickolsky MS, Kvashnina KO. Probing the Local Atomic Structure of In and Cu in Sphalerite by XAS Spectroscopy Enhanced by Reverse Monte Carlo Algorithm. Minerals. 2020; 10(10):841. https://doi.org/10.3390/min10100841

Chicago/Turabian Style

Trigub, Alexander L.; Trofimov, Nikolay D.; Tagirov, Boris R.; Nickolsky, Max S.; Kvashnina, Kristina O. 2020. "Probing the Local Atomic Structure of In and Cu in Sphalerite by XAS Spectroscopy Enhanced by Reverse Monte Carlo Algorithm" Minerals 10, no. 10: 841. https://doi.org/10.3390/min10100841

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