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.