Structure cristalline du composé intermétallique Ni18Ge12

Single crystals of octa-deca-nickel dodeca-germanide were grown by chemical transport reaction. The inter-metallic compound crystallizes in a superstructure of the hexa-gonal NiAs type (B8 type). All atoms in the asymmetric unit lie on special positions except one Ni atom (two Ni atoms have site symmetry -6.. and another one has site symmetry .2. while the Ge atoms have site symmetries 32., m.. and 3..). In the structure, the Ni atoms are arranged in 11- or 13-vertex polyhedra (CN = 11-13). The coordination polyhedra of the Ge atoms are bicapped square anti-prisms (CN = 10) or 11-vertex polyhedra (CN = 11). The structure exhibits strong Ge⋯Ni inter-actions, but no close Ge⋯Ge contacts are observed. The Ni atoms with CN = 13 form infinite chains along [001] with an Ni-Ni distance of 2.491 (2) Å.