Synthesis, crystal and electronic structure of BaLi2Cd2Ge2

A new quatemary germanide has been synthesized and structurally characterized. BaLi2Cd2Ge2 adopts the rhombohedral CaCu4P2 structure type (Pearson code hR7; space group R (3) over barm, Z = 3) with unit cell parameters a = 4.5929(6) and c= 26.119(5) angstrom. Structure refinements from single-crystal X-ray diffraction data demonstrate that the layered crystal structure can be regarded as an ordered quaternary variant of the ternary archetype; structural parallels to layered pnictides and binary germanides can also be drawn. The layered crystal structure is characterized by the absence of direct Ge-Ge and Cd-Cd homoatomic bonds, which suggests that BaLi2Cd2Ge2 should be classified as a Zintl phase, according to the formulation (BA(2+))(Li+)(2) (Cd2+)(2)(Ge-4(-))(2). Electronic structure calculations show that the Fermi level crosses a distinct peak in the DOS, although the presence of an electronic band gap or a dip in the electronic density of states at the Fermi level is expected based on the electron partitioning.