The structure of multiple twinned CsMgInF6 and its relationship to other pyrochlore derived fluorides
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Karen Friese
Abstract
The pyrochlore derived fluoride structures with general composition AM2+M3+F6 crystallize in space groups which are in group-subgroup relationship to Fd-3m, the space group of the archetype pyrochlore structure. All orthorhombic representatives investigated so far show an ordered M2+/M3+ distribution over two symmetrically independent octahedral sites. CsMgInF6 crystallizes in space group Pnma with lattice parameters a = 7.5285(1), b = 7.5285(1) and c = 10.6459(1) Å. The investigated crystal was a second degree twin, where the independent twin elements are a combination of the three- and fourfold rotation axes of the archetype cubic lattice. The pseudosymmetry of the compound with respect to space group Imma is extremely high and a reliable decision about the correct symmetry was only possible when inspecting partial agreement factors for the weak reflections h + k + l = 2n + 1 only. With respect to the other orthorhombic pyrochlore derived ter nary fluorides, the present compound differs in the fact that the M2+/M3+ ions are completely disordered in CsMgInF6.
© by Oldenbourg Wissenschaftsverlag, München
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Articles in the same Issue
- Stoichiometric valence versus structural valence: Conclusions drawn from a study of the influence of polyhedron distortion on bond valence sums
- An alternative expression for counting the number of close-packed polytypes
- Calculation of the BO3 triangle to BO4 (PO4) tetrahedron ratio for borates and borophosphates based on the O bond numbers in the anion complexes
- Incommensurate modulation at 165 °C of intermediate tridymite
- The structure of multiple twinned CsMgInF6 and its relationship to other pyrochlore derived fluorides
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- Polymorphs of 2,3-diphenyl maleic acid anhydride and 2,3-diphenyl maleic imide: Synthesis, crystal structures, lattice energies and fluorescence
- Synthesis, crystal structure and electrochemical behaviour of water soluble Schiff bases
- Structure determination without Fourier inversion. Part I. Unique results for centrosymmetric examples
- On sphere packings of arbitrarily low density
