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Total scattering studies of silica polymorphs: similarities in glass and disordered crystalline local structure

Published online by Cambridge University Press:  05 July 2018

D. A. Keen*
Affiliation:
ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK
M. T. Dove
Affiliation:
Department of Earth Sciences, Cambridge University, Downing Street, Cambridge CB2 3EQ, UK
*

Abstract

The structure of amorphous silica has frequently been compared with its crystalline counterparts in an attempt to understand the glass structure beyond short-range correlations. This paper presents results from neutron total scattering measurements of several polymorphs of silica and shows how these can be used to make a direct, quantitative comparison of amorphous and crystalline forms. It is found that the glass is similar to HP-tridymite and β-cristobalite, both dynamically-disordered crystalline phases of silica, but only out to distances ∼7.5 Å, beyond which the structures diverge. This is too small to validate a microcrystallite theory of glass structure. It is the average 180° Si–O–Si linkage in these two crystalline phases which gives them the flexibility for their instantaneous disordered structure to resemble the quenched (static) glass structure.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2000

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