Chemistry with covalent intermetallic compounds

Covalent intermetallic compounds are one manifestation of so-called confined metals. Although they are metals, these materials show structural and bonding characteristics of covalently bonded semiconductors. This very special state of matter “on the edge of covalency” has remarkable physical properties but also unusual chemical stability. A deeper understanding of the chemical interactions and their relation to the metallic ground state is of great conceptual interest. This insight would allow a better chemical predictability of the structure and related properties of such compounds. Quantum chemical bonding analysis represents a long-term focus at MPI-CPfS, and this expertise shall be employed and further developed in this project. DFT calculations on prototype compounds and compound classes will be accompanied by development of new applications and tools for bonding analysis.

On the experimental side, the highly covalent and thus chemically inert part of the structure is typically formed by the heavier elements of the p-block, such as gallium, germanium, tin or bismuth. The other partner, e.g. an alkaline metal, can skillfully be extracted by soft chemistry methods. The application of this innovative concept has, for example, led to the discovery of new element modifications. In this project, the above approach shall be extended to ternary intermetallic compounds that contain an electron-rich transition metal. The latter is typically strongly bonded to the p-block element forming a stable substructure, which can be a framework, a layer or a rod. Topochemical extraction of the alkaline atoms in a heterogeneous reaction should result in hitherto unknown (metastable) compounds with fully unpredictable properties. The unique expertise of MPI-CPfS and TU Dresden in this new field of synthetic solid-state chemistry will be combined. Characterisation of products by chemical analysis, diffraction, electron microscopy and spectroscopy will be accompanied by quantum-chemical bonding analysis and evaluation of physical properties.

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