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Schlagwörter:
BaAl4 structure type, Gallium, Single crystal, Sodium, Translation symmetry violation, Aluminum compounds, Annealing, Barium alloys, Barium compounds, Cerium compounds, Cesium compounds, Crystal atomic structure, Crystal defects, Crystal symmetry, Gallium, Gallium compounds, Selenium compounds, Spectroscopic analysis, Baal4 structure type, Compositional homogeneity, Crystals structures, Na atoms, Single phasis, Structure type, Symmetry violation, Tantalum ampoules, Translation symmetry, Translation symmetry violation, Single crystals
Zusammenfassung:
Single-phase NaGa4 samples were prepared by annealing stoichiometric element mixtures at 200 °C, 300 °C, and 450 °C in closed tantalum ampoules. No compositional homogeneity range was detected. While single crystals annealed at 200 °C feature a fully ordered crystal structure, a crystal annealed at 300 °C reveals a defect with mutual exchange of Na atoms and Ga2 dumbbells. The structure motif caused by the violation of translational symmetry resembles the CeMg2Si2 type of structure. The NaGa4 structure constitutes a branch of the BaAl4 type distinguished by a notably high c/a ratio (space group I4/mmm; a=4.2261(1) Å, c=11.2633(6) Å, c/a=2.67). This distortion enables the adaption of the BaAl4-type to small cations, when the further shortening of the apical–apical distance d(Ga–Ga) is not possible any more. Therefore, NaGa4 offers an adaption alternative to the monoclinic distortion observed in CaGa4 and YbGa4. Conductivity measurements validate the metallic behavior anticipated by NMR measurements in earlier studies. © 2024 The Author(s). Chemistry
