Lithium-stuffed diamond polytype Zn-Tt structures (Tt = Sn, Ge): the two lithium-zinc-tetrelides Li3Zn2Sn4 and Li2ZnGe3.

In view of the search for alternative structures for Li ion battery materials and electron-poor framework semiconductors for thermoelectric applications, the systems Li–Zn–Tt with Tt = Ge or Sn were investigated. Li3Zn2Sn4 and Li2ZnGe3 were obtained by high-temperature syntheses from the elements. The crystal structures of both phases were determined with single-crystal X-ray diffraction methods and the electronic structure of Li3Zn2Sn4 was analyzed by means of DFT calculations (TB-LMTO-ASA). Both phases show diamond polytype analogous Zn–Tt networks with tetrahedrally four-coordinated Zn and Tt atoms. The new phase Li3Zn2Sn4 crystallizes in space group P63/mmc (No. 194) with lattice parameters a = 4.528(1) A and c = 22.119(2) A. Zn and Sn atoms are fully ordered on three sites that constitute a 6H diamond polytype like network. Li2ZnGe3 is also described in space group P63/mmc (No. 194) with lattice parameters a = 4.167(1) A and c = 6.754(1) A. The Zn–Ge substructure is a hexagonal diamond (2H polytype) ...