Abstract
Leucites are tetrahedrally coordinated silicate framework structures with some of the silicon framework cations partially replaced by divalent or trivalent cations. These structures have general formulae A2BSi5O12 and ACSi2O6; where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation. In this paper, we report the Rietveld refinements of three more synthetic leucite analogues with stoichiometries of Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6. Cs2NiSi5O12 is Ia$\bar{3}$d cubic and is isostructural with Cs2CuSi5O12. RbGaSi2O6 is I41/a tetragonal and is isostructural with KGaSi2O6. CsGaSi2O6 is $I\bar{4}3d$ cubic and is isostructural with RbBSi2O6.
Highlights
Synthetic anhydrous analogues of the silicate framework minerals leucite (KAlSi2O6) and pollucite (CsAlSi2O6) can be prepared with the general formulae A2BSi5O12 and ACSi2O6; where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation
We report the Rietveld refinements (Rietveld, 1969) of three more tetrahedrally coordinated sites (T-sites) cation-disordered synthetic leucite analogues with stoichiometries of Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6
Crystal structures have been refined for Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6 leucite analogues from X-ray powder diffraction (XRD) data
Summary
Synthetic anhydrous analogues of the silicate framework minerals leucite (KAlSi2O6) and pollucite (CsAlSi2O6) can be prepared with the general formulae A2BSi5O12 and ACSi2O6; where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation. These structures all have the same topology with B and C cations partially substituting onto tetrahedrally coordinated sites (T-sites) in the silicate framework and charge balancing A cations sitting in extra-framework channels. RbCsX2+Si5O12 (X = Mg, Ni, Cd) leucite analogues, with two different extra-framework alkali metal cations, all have the Pbca structure with ordered T-site cations (Bell and Henderson, 2019). We report the Rietveld refinements (Rietveld, 1969) of three more T-site cation-disordered synthetic leucite analogues with stoichiometries of Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6
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