Penta­zirconium copper tribismuth

Penta­zirconium copper tribismuth, Zr₅CuBi₃, crystallizes in the hexa­gonal Hf₅CuSn₃ structure type. The asymmetric unit contains two Zr sites (site symmetries 3.2 and m2m), one Cu site (site symmetry 3.m) and one Bi site (site symmetry m2m). The environment of the Bi atoms is a tetra­gonal anti­prism with one added atom and a coordination number (CN) of 9. The polyhedron around the Zr1 atom is a defective cubo­octa­hedron with CN = 11. The bicapped hexa­gonal anti­prism (CN = 14) is typical for Zr2 atoms. The Cu atom is enclosed in a eight-vertex polyhedron (octa­hedron with two centered faces). The metallic type of bonding was indicated by an analysis of the inter­atomic distances and electronic structure calculation data.

Thulium nickel/lithium distannide, TmNi_1-xLi_xSn₂ (x = 0.035)

The quaternary thulium nickel/lithium distannide, TmNi_1-xLi_xSn₂ (x = 0.035), crystallizes in the ortho­rhom­bic LuNiSn₂ structure type. The asymmetric unit contains three Tm sites, six Sn sites, two Ni sites and one Ni/Li site [relative occupancies = 0.895 (8):0.185 (8)]. Site symmetries are .m. for all atoms. The 17-, 18- and 19-vertex distorted pseudo-Frank-Kasper polyhedra are typical for all Tm atoms. Four Sn atoms are enclosed in a 12-vertex deformed cubo­octa­hedron, and another Sn atom is enclosed in a penta­gonal prism with three added atoms. A tricapped trigonal prism is typical for a further Sn atom. The coordination number for all Ni atoms and Ni/Li statistical mixtures is 12 (fourcapped trigonal prism [Ni/LiTm₅Sn₅]). Tm atoms form the base of a prism and Ni/Li atoms are at the centres of the side faces of an [SnTm₆Ni/Li₃] prism. These isolated prisms are implemented into three-dimensional-nets built out of Sn atoms. Electronic structure calculations using TB-LMTO-ASA suggest that the Tm and Ni/Li atoms form positively charged n[TmNi/Li]^m+ polycations which compensate the negative charge of 2n[Sn]^m- polyanions. Analysis of the inter­atomic distances and electronic structure calculations indicate the dominance of a metallic type of bonding.