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Synchrotron radiation diffraction study of the mineral moolooite, and synthetic copper oxalates

Published online by Cambridge University Press:  07 March 2019

B. H. O'Connor*
Affiliation:
Department of Physics and Astronomy, Curtin University, Kent St, Bentley, Perth, WA 6102, Australia
R. M. Clarke
Affiliation:
ChemCentre, PO Box 1250, Bentley, WA 6983, Australia
J. A. Kimpton
Affiliation:
Australian Synchrotron, 800 Blackburn Road, Clayton, Vic 3168, Australia
*
a)Author to whom correspondence should be addressed. Electronic mail: brian_oconnor@iprimus.com.au

Abstract

The orthorhombic mineral moolooite, CuC2O4. nH2O, described by Clarke and Williams (1986) using Debye-Scherrer photographic data, has a fully-disordered stacking fault (FDSF) structure. Related monoclinic models have been reported for various synthesised samples based on Schmittler (1968). In the present study, synchrotron radiation diffraction data for moolooite and synthesised specimens have been examined with particular reference to crystallographic disorder. The moolooite data correspond to space group Pnnm, with a = 5.3064(2), b = 5.6804(2), c = 2.5630(1) Å; Vc = 77.26(1) Å3; and Z = 1; and the FDSF structure along the b-direction has been confirmed. The synthetic specimen data from the study indicate partial ordering, with space group P21/n; and the cell parameters for one specimen being a = 5.957(7), b = 5.611(5), c = 5.133(7) Å; β = 115.16(2)°; Vc = 155.27 Å3 and Z = 2. The level of zeolitic water in the materials has been considered using the approach of Schmittler based on thermogravimetry and pycnometry. The new data for natural topotype material correspond to CuC2O4.1.0H2O. It is postulated that the level of water for natural and synthetic specimens may be attributed to the conditions under which the material forms.

Type
Technical Article
Copyright
Copyright © International Centre for Diffraction Data 2019 

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