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Thermal response of structure and hydroxyl ion of phengite-2M (sub 1) ; an in situ neutron diffraction and FTIR study

Mainak Mookherjee, Simon A. T. Redfern and Ming Zhang
Thermal response of structure and hydroxyl ion of phengite-2M (sub 1) ; an in situ neutron diffraction and FTIR study (in Experimental mineralogy, petrology and geochemistry, Anonymous)
European Journal of Mineralogy (June 2001) 13 (3): 545-555

Abstract

The thermal dependence of the structure of natural phengite-2M (sub 1) with chemical formula (K (sub 0.95) Na (sub 0.05) )(Al (sub 0.76) Fe (sub 0.14) Mg (sub 0.10) ) (sub 2) (Si (sub 3.25) Al (sub 0.75) )O (sub 10) (OH (sub 1.96) F (sub 0.04) ) has been studied by in situ neutron diffraction. The short-range correlated behaviour of the hydroxyl group was probed by FTIR spectroscopy while the long-range correlated hydroxyl structure was studied by neutron diffraction. Changes in long-range ordering of Si and Al on the tetrahedral sites were not observed from neutron diffraction. Structure refinement of the neutron diffraction data by the Rietveld method suggested that the apparent average hydroxyl bond length decreases on heating. The infrared data show a decrease in the stretching frequency of hydroxyl group, however. Possible explanations for these results are explored. It seems most likely that the apparent shortening of the hydroxyl bond length may be an artefact due to an increase in its vibrational amplitude. The anisotropic vibration of the hydroxyl bond as revealed by the anisotropic displacement parameters of H, increases so much that the average length (shown by the neutron refinement) appears to decrease at high temperatures while the local length of the bond, as indicated by FTIR results, increases.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 13
Serial Issue: 3
Title: Thermal response of structure and hydroxyl ion of phengite-2M (sub 1) ; an in situ neutron diffraction and FTIR study
Title: Experimental mineralogy, petrology and geochemistry
Author(s): Mookherjee, MainakRedfern, Simon A. T.Zhang, Ming
Author(s): Anonymous
Affiliation: University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Pages: 545-555
Published: 200106
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
Meeting name: Eighth international symposium on Experimental mineralogy, petrology and geochemistry
Meeting location: Bergamo, ITA, Italy
Meeting date: 20000416April 16-19, 2000
References: 33
Accession Number: 2001-055199
Categories: Mineralogy of silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200117
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