1. Syntheses and crystal structures of the quaternary thiogermanates Cu4FeGe2S7 and Cu4CoGe2S7.
- Author
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Craig, Andrew J., Stoyko, Stanislav S., Bonnoni, Allyson, and Aitken, Jennifer A.
- Subjects
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QUATERNARY structure , *SILVER sulfide , *CRYSTAL structure , *X-ray powder diffraction , *STRUCTURAL frames , *THERMAL analysis , *IRON compounds - Abstract
The quaternary thiogermanates Cu4FeGe2S7 (tetracopper iron digermanium heptasulfide) and Cu4CoGe2S7 (tetracopper cobalt digermanium heptasulfide) were prepared in evacuated fused-silica ampoules via high-temperature, solid-state synthesis using stoichiometric amounts of the elements at 1273 K. These isostructural compounds crystallize in the Cu4NiSi2S7 structure type, which can be considered as a superstructure of cubic diamond or sphalerite. The monovalent (Cu+), divalent (Fe2+ or Co2+) and tetravalent (Ge4+) cations adopt tetrahedral geometries, each being surrounded by four S2− anions. The divalent cation and one of the sulfide ions lie on crystallographic twofold axes. These tetrahedra share corners to create a three-dimensional framework structure. All of the tetrahedra align along the same crystallographic direction, rendering the structure non-centrosymmetric and polar (space group C2). Analysis of X-ray powder diffraction data revealed that the structures are the major phase of the reaction products. Thermal analysis indicated relatively high melting temperatures, near 1273 K. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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