Temporary Cohabitation: The Metastable Phase Au4Si

Julia Maria Hübner, Brenna C. Bierman, Reine Wallenberg, Daniel C. Fredrickson

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)21016-21021
Number of pages6
JournalJournal of the American Chemical Society
Issue number46
Publication statusPublished - 2022 Nov

Subject classification (UKÄ)

  • Condensed Matter Physics


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