The low-temperature behaviour of cancrinite : an in situ single-crystal X-ray diffraction study
Articolo
Data di Pubblicazione:
2012
Citazione:
The low-temperature behaviour of cancrinite : an in situ single-crystal X-ray diffraction study / G.D. Gatta, P. Lotti, V. Kahlenberg, U. Haefeker. - In: MINERALOGICAL MAGAZINE. - ISSN 0026-461X. - 76:4(2012 Aug), pp. 933-948.
Abstract:
The low-temperature structural behaviour of natural cancrinite with a formula Na 6.59Ca 0.93[Si 6.12Al 5.88O 24](CO 3) 1.04F 0.41•2H 2O has been investigated by means of in situ single-crystal X-ray diffraction and Raman spectroscopy. High quality structure refinements were obtained at 293, 250, 220, 180, 140, 100 and at 293 K again (at the end of the low-T experiments). The variation in the unit-cell volume as a function of temperature (T) exhibits a continuous trend, without any evident thermoelastic anomaly. The thermal expansion coefficient α V = (1/V)∂V/∂T is 3.8(7) × 10 -5 K -1 (between 100 and 293 K). The structure refinement based on intensity data collected at ambient conditions after the low-T experiment confirmed that the low-T induced deformation processes are completely reversible. The extraframework population does not show significant variations down to 100 K. The strong positional disorder of the carbonate groups along the c axis persists within the T range investigated. The structural behaviour of cancrinite at low-T is mainly governed by the continuous framework rearrangement through the ditrigonalization of the six-membered rings which lie in a plane perpendicular to [0001], the contraction of the four-membered ring joint units, the decrease of the ring corrugation in the (0001) plane, and the flattening of the cancrinite cages. A list of the principal Raman active modes in ambient conditions is provided and discussed.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
cancrinite; low temperature; single-crystal X-ray diffraction; structure refinement
Elenco autori:
G.D. Gatta, P. Lotti, V. Kahlenberg, U. Haefeker
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