EXAFS STUDY OF RARE-EARTH ELEMENT COORDINATION IN CALCITE
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dc.contributor.author | Elzinga E.J. | |
dc.contributor.author | Reeder R.J. | |
dc.contributor.author | Withers S.H. | |
dc.contributor.author | Peale R.E. | |
dc.contributor.author | Mason R.A. | |
dc.contributor.author | Beck K.M. | |
dc.contributor.author | Hess W.P. | |
dc.date.accessioned | 2021-04-20T03:35:24Z | |
dc.date.available | 2021-04-20T03:35:24Z | |
dc.date.issued | 2002 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=1232928 | |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 2002, 66, 16, 2875-2885 | |
dc.identifier.issn | 0016-7037 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/28189 | |
dc.description.abstract | Extended X-ray absorption fine-structure (EXAFS) spectroscopy is used to characterize the local coordination of selected rare-earth elements (Nd3+, Sm3+, Dy3+, Yb3+) coprecipitated with calcite in minor concentrations from room-temperature aqueous solutions. Fitting results confirm substitution in the Ca site, but first-shell Nd-O and Sm-O distances are longer than the Ca-O distance in calcite and longer than what is consistent with ionic radii sums for sixfold coordination in the octahedral Ca site. In contrast, first-shell Dy-O and Yb-O distances are shorter than the Ca-O distance and are consistent with ionic radii sums for sixfold coordination. Comparison of Nd-O and Sm-O bond lengths with those in lanthanide sesquioxides and with ionic radii trends across the lanthanide series suggests that Nd3+ and Sm3+ have sevenfold coordination in a modified Ca site in calcite. This would require some disruption of the local structure, with an expected decrease in stability, and possibly a different charge compensation mechanism between Nd and Sm vs. Yb and Dy. A possible explanation for the increased coordination for the larger rare-earth elements involves bidentate ligation from a CO3 group. Because trivalent actinides such as Am3+ and Cm3+ have ionic radii similar to Nd3+, their incorporation in calcite may result in a similar defect structure. | |
dc.title | EXAFS STUDY OF RARE-EARTH ELEMENT COORDINATION IN CALCITE | |
dc.type | Статья |
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