Sulfur K-edge XANES study of local electronic structure in ternary monosulfide solid solution [(Fe, Co, Ni)0.923S] |
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Authors: | S P Farrell M E Fleet |
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Institution: | (1) Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, Canada e-mail: spfarrel@julian.uwo.ca Tel.: +1 519-661-3184; Fax: +1 519-661-3198, CA |
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Abstract: | Synchrotron radiation S K-edge XANES spectra and unit-cell parameters are used to investigate the local electronic structure
of non-stoichiometric binary and ternary Fe-Co-Ni monosulfide solid solution (mss; M0.923S, M = Fe, Co, Ni) quenched from 800 °C and low pressure. The prominent absorption edge feature of the XANES spectra represents
transition of S 1s core level electrons to unoccupied S 3p σ* antibonding orbitals hybridized with empty metal 3d(eg) orbitals. There is a progressive increase in area of the edge peak from Fe0.923S to Ni0.923S and Co0.923S, which correlates with progressive decrease in c and a parameters for the NiAs-type subcell and increase in metallic character, and reflects increase in the number and availability
of empty eg
β orbitals and covalence of metal-S bonds. More generally, the area of the edge peak exhibits an inverse linear correlation
with a, c and unit-cell volume of binary and ternary mss. This inverse linear correlation is attributed to progressive increase in
covalence and M-S-M bonding interaction in the c-axis direction, through metal-S M 3d(eg) - S 3p (or 3d)] π bonding. However, the area of the edge peak does not correlate very well with the average number of 3d
electrons per metal atom in these solid solutions, showing that the absorption of synchrotron radiation reflects the local
electronic structure of individual absorber atoms (i.e. the SM6 cluster), and is not a group (crystal energy band) effect.
Received: 21 March 2000 / Accepted: 14 July 2000 |
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Keywords: | Semiconductors Electronic band structure EXAFS NEXAFS SEXAFS Synchrotron radiation X-ray spectroscopy |
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