Abstract

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.