Ca2Pd3Ge, a new fully ordered ternary Laves phase structure

The title compound, Ca2Pd3Ge, was prepared as a part of a systematic investigation of the Ca–Pd–Ge ternary phase diagram. The structure was determined and refined from single-crystal X-ray diffraction data. It is a new fully ordered ternary Laves phase with the space group R-3m, Z=3, a=5.6191 (5) Å, c=12.1674 (7) Å, wR2=0.054 (all data) and is isostructural to Mg2Ni3Si (Noréus et al., 1985 [17]) but due to the larger size of all elements in Ca2Pd3Ge, the cell axes are approximately 10% longer. The compound may formally be considered as a Zintl compound, with [Pd3Ge]4− forming a poly-anionic network and divalent Ca cations located in truncated tetrahedral interstices. The electronic structure and chemical bonding of Ca2Pd3Ge is discussed in terms of LMTO band structure calculations and compared with CaPd2 (MgCu2-type).