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Refinement of hydrogen positions in natural chondrodite by powder neutron diffraction: implications for the stability of humite minerals

Published online by Cambridge University Press:  05 July 2018

A. J. Berry*
Affiliation:
Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
M. James
Affiliation:
Neutron Scattering Group, Building 58, Australian Nuclear Science and Technology Organisation, PMB 1, Menai NSW 2234, Australia
*

Abstract

The structure of a natural sample of chondrodite (Mg4.89Fe0.07Si2.04O8F1.54(OH)0.46) was refined using powder neutron diffraction data and the Rietveld technique (P21/b; Z = 2; a = 4.7204(1)Å; b = 10.2360(3)Å; c = 7.8252(2)Å; α = 109.11(1)°; V = 357.26(2)Å3). Hydrogen was found to occupy the H1 site. The significance of hydrogen at this site is discussed in terms of hydrogen-bond stabilization of humite structures containing varying amounts of OH, F and Ti. Arguments are proposed as to why the F and Ti contents of natural humites usually result in only one H per formula unit when there is no crystal-chemical reason why fully hydrated samples should not be favoured.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2002

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