TbNb6Sn6: the first ternary compound from the rare earth–niobium–tin system

Abstract

The title compound, terbium hexaniobium hexastannide, TbNb6Sn6, is the first ternary compound from the rare earth–niobium–tin system. It has the HfFe6Ge6 structure type, which can be analysed as an intergrowth of the Zr4Al3 and CaCu5 structures. All the atoms lie on special positions; their coordination geometries and site symmetries are: Tb (dodecahedron) 6/mmm; Nb (distorted icosahedron) 2mm; Sn (Frank–Caspar polyhedron, CN = 14–15) 6mm and overline{6}m2; Sn (distorted icosahedron) overline{6}m2. The structure contains a graphite-type Sn network, Kagome nets of Nb atoms, and Tb atoms alternating with Sn2 dumbbells in the channels.