Preparation and Structure of a New Germanium Clathrate, Ba24Ge100

Single crystals of a new germanium clathrate, Ba24Ge100, were synthesized by the Czochralsky pulling method using a tetra-arc furnace under an Ar atmosphere. The crystal structure was studied by X-ray single-crystal analysis. The clathrate crystallized in the cubic space group P4132 with a=14.5635(7) ?, V=3088.9(2) ?3. The final refinement using 903 unique reflections converged at R=0.032 and Rw=0.036. In the structure, germanium atoms are linked by sp3-bonds to form a three-dimensional network, in which barium atoms are enclosed. There are three sites for the barium atoms having different coordination environments. One site is in a Ge20 dodecahedron and the others are coordinated with 20 Ge atoms and 8 Ge atoms, respectively.