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- Title
Daliranite, PbHgAs<sub>2</sub>S<sub>5</sub>: determination of the incommensurately modulated structure and revision of the chemical formula.
- Authors
Lanza, Arianna E.; Gemmi, Mauro; Bindi, Luca; Mugnaioli, Enrico; Paar, Werner H.
- Abstract
The incommensurately modulated crystal structure of the mineral daliranite has been determined using 3D electron diffraction data obtained on nanocrystalline domains. Daliranite is orthorhombic with a = 21, b = 4.3, c = 9.5 Å and shows modulation satellites along c. The solution of the average structure in the Pnma space group together with energy‐dispersive X‐ray spectroscopy data obtained on the same domains indicate a chemical formula of PbHgAs2S5, which has one S fewer than previously reported. The crystal structure of daliranite is built from columns of face‐sharing PbS8 bicapped trigonal prisms laterally connected by [2+4]Hg polyhedra and (As3+2S5)4− groups. The excellent quality of the electron diffraction data allows a structural model to be built for the modulated structure in superspace, which shows that the modulation is due to an alternated occupancy of a split As site.
- Subjects
CHEMICAL formulas; CHEMICAL structure; ELECTRON diffraction; X-ray spectroscopy; CRYSTAL structure; MODULATION spectroscopy
- Publication
Acta Crystallographica Section B: Structural Science, Crystal Engineering & Materials, 2019, Vol 75, Issue 4, p711
- ISSN
2052-5192
- Publication type
Article
- DOI
10.1107/S2052520619007340