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Structural behaviour of chkalovite, Na2BeSi2O6: a member of the cristobalite family*

Published online by Cambridge University Press:  05 July 2018

C.M.B. Henderson  and
D. Taylor
C.M.B. Henderson
Affiliation:
Department of Geology, The University, Manchester M13 9P1
D. Taylor
Affiliation:
Department of Geology, The University, Manchester M13 9P1
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Abstract

The atomic structure of chkalovite, Na2BeSi2O6, has been determined and refined by Simonov et al. (1976). It is orthorhombic, space group Fdd2, with cell parameters: a = 21.129 (5), b = 6.881 (2), and c = 21.188 (5)/Å. The structure is very similar to that of alpha-cristobalite (Dollase, 1965), comprising a framework of ordered BeO4 and SiO4 tetrahedra with the sodium atoms occupying sites within the cavities of the beryllosilicate framework. Taylor (1972) developed a tilting model for the cristobalite structure assuming regular tetrahedra. In addition to the single tilt system deduced for cristobalite (Taylor, 1972, 1984a) chkalovite has secondary tilt systems involving a slight adjustment of the structure by a small cooperative tilt or twist of some tetrahedra about one or more of their three-fold axes (see fig. 1 of Simonov et al., 1976).

Keywords

chkaloviteNa2BeSi2O6thermal expansioncristobalite
Type
Short Communications
Information
Mineralogical Magazine , Volume 53 , Issue 369 , March 1989 , pp. 117 - 119
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1989

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References

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