Thulium nickel/lithium distannide, TmNi1xLixSn2 (x = 0.035)

disorder in main residue; R factor = 0.026; wR factor = 0.060; data-to-parameter ratio = 17.2. The quaternary thulium nickel/lithium distannide, TmNi1x-LixSn2 (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 poly-anions. Analysis of the interatomic distances and electronic structure calculations indicate the dominance of a metallic type of bonding. Related literature For isotypic structures, see: Komarovskaya et al. (1983). For background of the study and related structures, see: Pavlyuk & Bodak (1992a,b); Pavlyuk et al. (1989a,b, 1991, 1993); Stetskiv et al. (2012, 2013). For electronic structure calculations, see: Andersen et al. (1986)