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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.
