| 1. |
- Akselrud, Lev, et al.
(författare)
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Order and disorder in the modulated phase hp-Mg9Ge5.1
- 2022
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Ingår i: Zeitschrift fur Anorganische und Allgemeine Chemie. - : Wiley. - 0044-2313 .- 1521-3749. ; 648:10
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Tidskriftsartikel (refereegranskat)abstract
- Single crystals of Mg9Ge5.1(2) were obtained at a pressure of 5 GPa in the temperature range 723 to 1273 K. The metastable high-pressure phase exhibits a crystal structure, which may be described as a host-guest variety of an UCl3-type framework. The atomic arrangement is characterized by a host crystal structure Mg9Ge3 with disordered germanium guests (≈2 Ge per formula unit) in the channels. The composite arrangement undergoes incommensurate modulation. Upon heating at ambient pressure, the phase transforms into the thermodynamically stable compounds Mg2Ge and Ge at 496(5) K. Measurements of the magnetic susceptibility indicate diamagnetic behavior between 75 and 350 K.
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| 2. |
- Freccero, Riccardo, et al.
(författare)
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New Insights into the Crystal Chemistry of FeB-Type Compounds : The Case of CeGe
- 2022
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 15:24
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Tidskriftsartikel (refereegranskat)abstract
- Several alkaline earth or rare earth binary monosilicides and -germanides possess complex bonding properties, such as polycation formation exceeding the scope of classical electron counting rules. In this study, we present characterization by powder and single-crystal diffraction and thermal analysis of CeGe, one of the few monogermanides crystallizing in the FeB-type structure. Comparative computational investigations for structure types experimentally observed for monogermanides and alternative structures with different structural motifs were performed to gain energetical insights into this family of compounds, underlining the preference for infinite germanium chains over other structural motifs. Formation enthalpy calculations and structural chemical analysis highlight the special position of FeB-type compounds among the monogermanides.
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| 3. |
- Hübner, Julia Maria, et al.
(författare)
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A Borosilicide with Clathrate VIII Structure
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:30, s. 13456-13460
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Tidskriftsartikel (refereegranskat)abstract
- The high-pressure phase Na8BxSi46-x(3 < x < 5) is the first representative of a borosilicide crystallizing in the rarely occurring clathrate VIII type structure. Crystals with composition Na8B4Si42(space group I43¯ m; a = 9.7187(2) Å Pearson symbol cI54) were obtained at 5-8 GPa and 1200 K. The clathrate I modification exists for the same composition at lower pressure with a larger cell volume (Pm3¯ n; a = 9. 977(2) Å cP54). Profound structural adaptions allow for a higher density of the clathrate VIII type than clathrate I, opening up the perspective of obtaining clathrate VIII type compounds as high-pressure forms of clathrate I.
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| 4. |
- Hübner, Julia Maria, et al.
(författare)
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Temporary Cohabitation : The Metastable Phase Au4Si
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:46, s. 21016-21021
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Tidskriftsartikel (refereegranskat)abstract
- The prediction, identification, and characterization of phases away from equilibrium conditions remain difficult challenges for material science. Herein, we demonstrate how systems whose phase diagrams contain deeply incising eutectics can offer opportunities to address these challenges. We report the synthesis of a new compound in the Au-Si system, a textbook example of a system with a deep eutectic. Au4Si crystallizes in a complex 18× 2×1 superstructure of the PtHg4type, based on the distortion of vertex-sharing Si@Au8cubes into bisdisphenoids. Au4Si decomposes upon heating and at room temperature even in high vacuum, highlighting its metastability. Electronic structure analysis reveals a pseudogap at the Fermi energy, which is enhanced by the superstructure through the relief of Au-Au antibonding interactions. The pseudogap is associated with a Zintl-type bonding scheme, which can be extended to the locally ordered liquid. These results highlight the potential for metastable phases to form in deep eutectics that preserve the local structures of the liquid.
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