BaNi_2Ge and Ca_4Ni_4Ge_3 - Two layered structures with ~2_∞[Ni_2Ge] and ~2_∞[Ni_4Ge_3] networks

摘要

The intermetallic compounds BaNi_2Ge and Ca_4Ni _4Ge_3 were prepared by melting stoichiometric amounts of the elements in welded tantalum ampoules in an induction furnace. The compounds were investigated by both powder and single-crystal X-ray diffraction. Both compounds crystallize in own structure types, BaNi_2Ge with space group Pmmn, a = 6.6935(5) ?, b = 4.1571(5) A, c = 5.9498(7) ?, wR2 = 0.043, 292 F~2 values, 16 variable parameters; Ca_4Ni _4Ge_3 with space group Cmcm, a = 4.1824(8) ?, b = 10.415(2) ?, c = 19.864(4) ?, wR2 = 0.061, 541 F~2 values, 38 variable parameters. The chemical bonding of these compounds is discussed in terms of TB-LMTO-ASA calculations and a topological analysis of the Electron Localization Function (ELF).