Study on A4BX6 compounds. I. Structure Refinement of Ternary Cd Halides A4CdX6 (A = NH4, K, Rb, In, Tl; X = Cl, I)

The refinement of the structures of rhombohedral (NH4)4CdCl6, K4CdCl6, and Rb4CdCl6 (K4CdCl6‐type) and of tetragonal In4CdI6 and Tl4CdI6 (Tl4HgBr6‐type) using single crystal data is reported. The discussion of the crystal chemistry of these compounds furnishes new structural relations and a first hint of the role, which ns2 cations play in these structures. All compounds of the A4BX6 family can clearly be separated with respect to their structure in a structure field diagram in the basis of the size relations A/X and B/X.