Synthesis and Crystal Structure of the New Quaternary Subnitride Na15Li8Ba12N6

The crystal structure of the new compound Na15Li8Ba12N6 has been determined from single-crystal X-ray diffraction data. It crystallizes in the trigonal system, space group with a = 12.3409(9) A, c = 33.311(4) A, Z = 3, and R1 = 0.037 (wR2 = 0.046) for 1912 reflections with Io>2σ(Io). The structure can be described as an fcc-type packing of Na tetrahedrons with Li8Ba12N6 clusters and centered Na hexagons in chair conformation among them. These hexagons together with some tetrahedral vertices connect to parallel infinite layers. By analogy with quaternary Na/Ba/Ca subnitrides this structure can be also regarded as a “salt in metal”.