Variable stoichiometry in tectosilicates having the leucite/pollucite-type structure with particular emphasis on modelling the interframework cavity cation environment

HENDERSON, C. M. B, BELL, Anthony and KNIGHT, K. S (2017). Variable stoichiometry in tectosilicates having the leucite/pollucite-type structure with particular emphasis on modelling the interframework cavity cation environment. Journal of solid state chemistry, 251, 90-104.

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Abstract

Unit cell data for synthetic samples of I41/a or Ia-3d AAlSi2O6(A=K,Rb,Tl,Cs) leucite/pollucites are compared to those for feldspar-stoichiometry leucite analogues (Rb,Tl,Cs)0.75□0.25Al0.75Si2.25O6. I41/a solid solutions between KAlSi2O6and KAlSi3O8(orthoclase feldspar, Or) and between K(Al0.85Fe0.15)Si2O6and Or both show increasing volumes and decreasing c/a with increasing Or. Phase relations are given for KAlSi3O8-RbAlSi3O8; monoclinic feldspars occur at low temperatures and I41/a leucites at higher temperatures; volumes of leucite solid solutions increase with increasing Rb. The cell volume of Rb0.75□0.25Al0.75Si2.25O6leucite is larger than that of RbAlSi2O6leucite. Published leucite/pollucite structures belonging to different Space Group symmetries are treated as having the cubic Ia-3d topology with a ‘pseudocell’ edge V1/3(V = unit cell volume); inequivalent site bond lengths and angles provide mean structural parameters for the cubic ‘pseudocells’. Multivariant linear regression equations using mean A – O distances as the independent variable were obtained using other structural parameters as dependent variables. Only two independent variables (V and mean tetrahedral ionic radius) are required to account for >90% of the variation. These regression equations can be used to predict the sizes of the cavity cation sites in leucite/pollucite-type phases of any stoichiometry.

Item Type:	Article
Uncontrolled Keywords:	0302 Inorganic Chemistry; 0303 Macromolecular And Materials Chemistry; 0306 Physical Chemistry (Incl. Structural); Inorganic & Nuclear Chemistry
Identification Number:	https://doi.org/10.1016/j.jssc.2017.04.013
Page Range:	90-104
SWORD Depositor:	Symplectic Elements
Depositing User:	Symplectic Elements
Date Deposited:	23 Jan 2019 11:54
Last Modified:	18 Mar 2021 06:49
URI:	https://shura.shu.ac.uk/id/eprint/23309

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