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- Title
Modulated vacancy ordering in SrGe<sub>6−</sub><sub>x</sub> (x≈0.45).
- Authors
Schwarz, Ulrich; Castillo, Rodrigo; Wosylus, Aron; Akselrud, Lev; Prots, Yurii; Wahl, Bernhard; Doert, Thomas; Bobnar, Matej; Grin, Yuri
- Abstract
The structural properties of modulated SrGe6−x (x≈0.45) were investigated by means of single-crystal and powder X-ray diffraction combined with quantum chemical calculations. The framework compound SrGe6−x adopts a defect variant of the EuGa2Ge4-type crystal structure. Samples of the binary compound with nominal compositions 0≤x≤0.5 were synthesized at pressures from 5 to 6 GPa and a temperature of typically 1400 K. The product reveals diffraction peaks of the EuGa2Ge4-type subcell plus additional reflections indicating an ordered superstructure. Detailed crystal structure analysis evidences the incommensurate nature of the superstructure and a modulation of the vacancy ordering in the germanium network. The computations have shown that the non-stoichiometric composition of the framework with its local defect organization affects the calculated charge of the strontium anions. Although the chemical composition is close to a charge-balanced situation, temperature-dependent resistivity measurements showed metal-type conductivity. At ambient pressure SrGe6−x decomposes exothermally and irreversibly at T=680(10) K into SrGe2 and germanium, indicating its metastable nature at ambient pressure.
- Subjects
X-ray diffraction; CRYSTAL structure; CRYSTALLIZATION; GERMANIUM; CHEMICAL reactions
- Publication
Zeitschrift für Naturforschung B: A Journal of Chemical Sciences, 2019, Vol 74, Issue 1, p137
- ISSN
0932-0776
- Publication type
Article
- DOI
10.1515/znb-2018-0200