Raman spectra of a low albite single crystal were collected during annealing at 1076 degrees C for up to 46 days. At seven annealing stages, the single crystal structure was refined by X-ray intensity data to determine the degree of Al-Si order using the tetrahedral bond distances. Single-crystal X-ray diffraction showed that residuals in the difference-Fourier map of the electron density and atomic displacement parameters of Si, O, and, most, Na, increase with Al-Si disorder. The Raman spectra show a significant broadening with disorder, and some slight peak shift. Three strong peaks, at 290 cm(-1) (nu(c)), 478 cm(-1) (nu(b)), and 507 cm(-1) (nu(a)) in ordered albite, were examined in further detail. nu(c) and nu(b) show a red-shift with broadening and Al-Si disorder; nu(a) blue-shifts with disorder and shows only a minor broadening. The broadening and shifts in Raman spectra are caused by structural deformation associated with Al-Si disorder. The nu(a) peak at 507 cm(-1) is the least affected by Al-Si disorder and is suitable to assess compositional changes in plagioclase. The Al-Si order can be determined in albite by the wavenumber difference Delta(ab) between the two main peaks nu(a) and nu(b) as follows: Q(od)(2) = 9.50(75) - 0.307(25)Delta(ab), R-2 = 0.94, where Q(od) is an order parameter derived from average tetrahedral Al-O and Si-O bond distances.
Al-Si ordering in albite : a combined single-crystal X-ray diffraction and Raman spectroscopy study / M. Tribaudino, G.D. Gatta, I. Aliatis, D. Bersani, P.P. Lottici. - In: JOURNAL OF RAMAN SPECTROSCOPY. - ISSN 0377-0486. - 49:12(2018), pp. 2028-2035.
|Titolo:||Al-Si ordering in albite : a combined single-crystal X-ray diffraction and Raman spectroscopy study|
GATTA, GIACOMO DIEGO (Secondo)
|Parole Chiave:||Al―Si order; high‐temperature annealing; plagioclase; X‐ray diffraction|
|Settore Scientifico Disciplinare:||Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul|
|Data di pubblicazione:||2018|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1002/jrs.5490|
|Appare nelle tipologie:||01 - Articolo su periodico|
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