BaNi₂Ge and Ca₄Ni₄Ge₃ - Two layered structures with ²_∞[Ni₂Ge] and ²_∞[Ni₄Ge₃] networks

The intermetallic compounds BaNi₂Ge and Ca₄Ni ₄Ge₃ 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, BaNi₂Ge with space group Pmmn, a = 6.6935(5) Å, b = 4.1571(5) A, c = 5.9498(7) Å, wR2 = 0.043, 292 F² values, 16 variable parameters; Ca₄Ni ₄Ge₃ with space group Cmcm, a = 4.1824(8) Å, b = 10.415(2) Å, c = 19.864(4) Å, wR2 = 0.061, 541 F² 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).