Grown from lithium flux, the ErCo5Si(3.17) silicide is a combination of disordered derivatives of the UCo5Si3 and Yb6Co30P19 structure types.

A ternary hexaerbium triacontacobalt enneakaidecasilicide, ErCo5Si(3.17), crystallizes as a combination of disordered variants of the hexagonal UCo5Si3 (P63/m) and Yb6Co30P19 (P6) structure types and is closely related to the Sc6Co30Si19 and Ce6Rh30Si19 types. The Er, Co and three of the Si atoms occupy sites of m.. symmetry and a fourth Si atom occupies a site of -6.. symmetry. The environment of the Er atom is a 21-vertex pseudo-Frank-Kasper polyhedron. Trigonal prismatic coordination is observed for the Si atoms. The Co atoms are enclosed in heavily deformed cuboctahedra and 11-vertex polyhedra. Crystallochemistry analysis and the data from electronic structure calculations (TB-LMTO-ASA) suggest that the Er atoms form positively charged cations which compensate the negative charge of the [Co12Si9](m-) polyanions.

Thulium nickel/lithium distannide, TmNi1-x Li x Sn2 (x = 0.035).

The quaternary thulium nickel/lithium distannide, TmNi1-x Li x Sn2 (x = 0.035), crystallizes in the ortho-rhom-bic 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 cubo-octa-hedron, and another Sn atom is enclosed in a penta-gonal 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 inter-atomic distances and electronic structure calculations indicate the dominance of a metallic type of bonding.

Crystal and electronic structures of La2LiGe6-x (x = 0.21) and La2LiGe4Si2.

The synthesis and characterization of a new ternary dilanthanum lithium hexagermanide, La(2)LiGe(6-x) (x = 0.21), belonging to the Pr(2)LiGe(6) structure type, and a quaternary dilanthanum lithium tetragermanium disilicide, La(2)LiGe(4)Si(2), which crystallizes as an ordered variant of this type, are reported. In both structures, Li is on a site of mmm symmetry. All other atoms are on sites of m2m symmetry. These structures are new representatives of a homologous linear structure series based on structural fragments of the AlB(2), CaF(2) and ZrSi(2) structure types. The observed 17-vertex polyhedra are typical for La atoms and the environment of the Li atom is cubic. Two Ge atoms are enclosed in a tetragonal prism with one added atom (nine-vertex polyhedron). The trigonal prismatic coordination is typical for Ge or Si atoms. The metallic nature of the bonding is indicated by the interatomic distances and electronic structure calculations.

Penta-terbium lithium tris-tannide, Tb(5)LiSn(3).

The new ternary phase penta-terbium lithium tris-tannide, Tb(5)LiSn(3), crystallizes in the hexa-gonal Hf(5)CuSn(3) structure type, which is a 'filled' version of the binary RE(5)Sn(3) phases (Mn(5)Si(3)-type) (RE is rare earth). The asymmetric unit contains two Tb sites (site symmetries 3.2 and m2m), one Li site (site symmetry [Formula: see text].m) and one Sn site (site symmetry m2m). The 14-vertex Frank-Kasper polyhedra are typical for Li and Tb atoms. The environment of the Sn atom is a pseudo-Frank-Kasper polyhedron with a coordination number of 13 for the tin atom. One of the Tb atoms is enclosed in a 17-vertex polyhedron. The metallic type of bonding was indicated by an analysis of the inter-atomic distances.