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- Title
Fluorite-related one-dimensional units in natural bismuth oxysulfates: the crystal structures of Bi<sub>14</sub>O<sub>16</sub>(SO<sub>4</sub>)<sub>5</sub> and Bi<sub>30</sub>O<sub>33</sub>(SO<sub>4</sub>)<sub>9</sub>(AsO<sub>4</sub>)<sub>2</sub>.
- Authors
Pinto, Daniela; Garavelli, Anna; Bindi, Luca
- Abstract
The crystal structures of two new natural Bi oxysulfates with the formula Bi14O16(SO4)5 [labelled new phase I; monoclinic, space group C2, a = 21.658 (4), b = 5.6648 (9), c = 15.092 (3) Å, β = 119.433 (11)° and Z = 2] and Bi30O33(SO4)9(AsO4)2 [labelled new phase II; triclinic, space group P1, a = 5.670 (3), b = 13.9408 (9), c = 22.7908 (18) Å, α = 80.903 (5), β = 82.854 (14), γ = 78.27 (2)° and Z = 1] from the high-temperature fumarole deposit of the La Fossa crater at Vulcano (Aeolian Islands, Italy) are reported. The structures are built up by a combination of fluorite-related Bi-O units and isolated (SO4)2− tetrahedra ( new phase I) or both (SO4)2− and (AsO4)3− tetrahedra ( new phase II). Owing to the effect of stereoactive lone pairs of Bi3+, Bi-O units in both the structures can be suitably described in terms of oxo-centered OBi4 tetrahedra. The structure of Bi14O16(SO4)5 is based upon one-dimensional [O16Bi14]10+ ribbons formed by six chains of edge-sharing OBi4 tetrahedra extending along [010]. In the structure of Bi30O33(SO4)9(AsO4)2 the same ribbon type coexists with another one-dimensional ribbon formed by seven chains of edge-sharing OBi4 tetrahedra and with the composition [O17Bi16]14+. Ribbons of the same type are joined by (SO4)2− and (AsO4)3− tetrahedra along [010] - if a reduced triclinic unit-cell setting is considered - so forming two different (001) slabs which alternate to each other along [001] and are joined by additional (SO4)2− tetrahedra. New phase I represents the natural analogues of synthetic Bi14O16(SO4)5, but with an ordered structure model.
- Subjects
CALCIUM fluoride; BISMUTH compounds; CRYSTAL structure
- Publication
Acta Crystallographica Section B: Structural Science, Crystal Engineering & Materials, 2015, Vol 71, Issue 5, p514
- ISSN
2052-5192
- Publication type
Article
- DOI
10.1107/S205252061501358X