BaGe6 and BaGe6‑x: Incommensurately Ordered Vacancies as Electron Traps

We report the high-pressure high-temperature synthesis of the germanium-based framework compounds BaGe6 (P = 15 GPa, T = 1073 K) and BaGe6–x (P = 10 GPa, T = 1073 K) which are metastable at ambient conditions. In BaGe6‑x, partial fragmentation of the BaGe6 network involves incommensurate modulations of both atomic positions and site occupancy. Bonding analysis in direct space reveals that the defect formation in BaGe6–x is associated with the establishment of free electron pairs around the defects. In accordance with the electron precise composition of BaGe6‑x for x = 0.5, physical measurements evidence semiconducting electron transport properties which are combined with low thermal conductivity.