An Unexpected Cubic Symmetry in Group IV Alloys Prepared Using Pressure and Temperature

The cubic diamond (Fd3‾ m) group IVA element Si has been the material driver of the electronics industry since its inception. We report synthesis of a new cubic (Im3‾ m) group IVA material, a GeSn solid solution, upon heating Ge and Sn at pressures from 13 to 28 GPa using double‐sided diamond anvil laser‐heating and large volume press methods. Both methods were coupled with in situ angle dispersive X‐ray diffraction characterization. The new material substantially enriches the seminal group IVA alloy materials landscape by introducing an eightfold coordinated cubic symmetry, which markedly expands on the conventional tetrahedrally coordinated cubic one. This cubic solid solution is formed, despite Ge never adopting the Im3‾ m symmetry, melting inhibiting subsequent Im3‾ m formation and reactant Ge and Sn having unlike crystal structures and atomic radii at all these pressures. This is hence achieved without adherence to conventional formation criteria and routes to synthesis. This advance creates fertile avenues for new materials development. New materials can be created without the need to follow conventional criteria and routes to synthesis. We demonstrate this for Ge–Sn, a system actively investigated for optoelectronic applications to overcome conventional cubic Si's deficiencies. Ge and Sn are however unreactive in the bulk, but we remove reactivity barriers and form a different structure, a simple new cubic solid solution.