Structure types – a review

Structures of binary inorganic A x B y compounds with A and B on two Wyckoff positions are characterized by the self‐coordination numbers T i , i = 1–3, of A and B atoms. The T 1 = 0–12 values of 122 structure types can be correlated with different topologies, A–A interactions and densities. High T 1 values like T 1 = 12 are obtained for fcc or hcp sphere packing with maximum density of A atoms and interstitial B atoms. Hexagonal or tetragonal layered compounds are recognized by the T i values 6 6 6 or 4 4 4. The T 1 = 2 values are found for chains, T 1 = 1 for ordered molecules like N 2 or Br 2 . The A and B atoms of few compounds like NaCl or CsCl form a pc or bcc sphere packing. The T 1 = 0 values of Na or Cs atoms indicate repulsive Na–Na or Cs–Cs interactions. Distorted structures of a structure type are recognized, if atoms with slightly different A–A or B–B distances are included in the proper coordination shells. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)