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Crystal structure of Na4[Cu4O2(SO4)4]·MeCl (Me: Na, Cu, ☐) – the synthetic Na-analogue of piypite (caratiite)
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- Journal:
- Mineralogical Magazine / Volume 64 / Issue 6 / December 2000
- Published online by Cambridge University Press:
- 05 July 2018, pp. 1099-1108
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- Article
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The crystal structure of Na4[Cu4O2(SO4)4] MeCl (Me: Na,Cu,☐) has been solved by direct methods and refined to R1 = 0.028 using 2466 independent reflections. The compound is tetragonal with space group P4/n, a = 18.451(1)Å, c = 4.9520(2)Å, Z = 4. The two main building units running parallel to the c-axis comprise: (1) slabs containing SO4 and OCu4 tetrahedra; and (2) chains of corner sharing Me(Cl,O)6 octahedra. The displacement ellipsoids of the atoms occupying the Me sites and of the Cl ions indicate a short-range static disorder. Copper in the slabs exhibits a (4+1) coordination. Both elements form a tunnel structure in which additional Na atoms are incorporated for charge compensation. The structure is closely related to the mineral piypite (K4Cu4O2(SO4)4 MeCl (Me: Na,Cu,☐)):
. Furthermore, the structure has a pronounced pseudo-translational symmetry: apart from some of the oxygen sites, all of the nineteen crystallographically distinct positions are related by a pseudo F centring.
. Furthermore, the structure has a pronounced pseudo-translational symmetry: apart from some of the oxygen sites, all of the nineteen crystallographically distinct positions are related by a pseudo F centring.