Cubic cation framework in trigonal structures of tourmalins: The core of structural type stability

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Marco E. Ciriotti
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Cubic cation framework in trigonal structures of tourmalins: The core of structural type stability

Messaggio da Marco E. Ciriotti » ven 22 set, 2017 9:40

Referenza:
▪ Borisov, S.V., Pervukhina, N.V., Magarill, S.A. (2017): Cubic cation framework in trigonal structures of tourmalins: The core of structural type stability. Journal of Structural Chemistry, 58, 809–812.

Abstract:
The crystallographic analysis of the tourmaline structure type with the general formula XY3Z6(T6O18)(BO3)3V3W (R3m, Z = 3, a ≈ 16 Å, c ≈ 7.2 Å) shows that tetrahedrally coordinated T (Si, Al, …) cations, octahedrally coordinated Z (Al, Fe, Mg), and Y (Fe, Mg, Mn, …) form a joint cation framework with a sublattice whose geometry is close to Fcub (aк ≈ 4.40 Å, αк ≈ 93°) with 40% vacant positions in it. The anion ordering is less regular.
Marco E. Ciriotti

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