Disorder in Rare Earth Metal Halide Carbide Nitrides

Single‐crystal X‐ray structure determinations of Ce 4 I 6 CN and disordered Ce 6 I 9 C 2 N phases are described together with electron‐microscopy studies of Ce 6 I 9 C 2 N and Y 6 I 9 C 2 N. Ce 4 I 6 CN crystallizes in the tetragonal space group P 4 2 / mnm with a = 13.877(2) Å, c = 9.665(2) Å. Compounds β′‐Ce 6 I 9 C 2 N and β″‐Ce 6 I 9 C 2 N crystallize in space group P 6/ m with a = 41.774(6) Å, c = 13.719(3) Å and a = 20.958(3) Å, c = 13.793(3) Å, respectively. The main structural feature of these compounds are rods of RE 6 C 2 octahedra and RE 4 N tetrahedra (RE = lanthanide) interconnected in different sequences. These rods are linked into Kagomé‐type frameworks with additional rods located in the centres of thehexagonal channels. The disorder patterns for these additional rods can be rationalized in terms of nearest‐neighbour interactions.