Synthesis, Structure and Chemical Bonding of Ba 2 Ni 5 Ge 4 – An Intermetallic Compound with a New Two‐dimensional $\rm^2_\infty$ [Ni 5 Ge 4 ] Structural Motif

The intermetallic compound Ba 2 Ni 5 Ge 4 was prepared by arc melting mixtures of the elements and subsequent annealing under argon. The compound crystallizes in a new structure type with the space group C 2/ m , Z = 2, a = 12.523(5) Å, b = 4.056(1) Å, c = 9.503(6) Å, β = 118.65(4)°, wR 2 = 0.086 (all data). Ba 2 Ni 5 Ge 4 consists of two‐dimensional $\rm^2_\infty$ [Ni 5 Ge 4 ] slabs that are separated by barium atoms. The slabs consist of a new combination of two structure motifs that are also present in other known intermetallic compounds in the system Ae /Ni/Ge ( Ae : Ca, Sr, Ba); namely $\rm^1_\infty$ [Ni 2 Ge 2 ] ribbons, which also occur in the low‐temperature modification of BaNi 2 Ge 2 , and distorted hexagonal prisms of the compositionNi@Ni 6 Ge 6 , that are present in the SrNi 3 Ge 2 structure type. The electronic structure and chemical bonding of Ba 2 Ni 5 Ge 4 is discussed in terms of LMTO band structure calculations and a topological analysis using the Electron Localization Function (ELF).