Review: Different types of ordering

Homogeneous structures A x B y with identical A–A or B–B self‐coordination numbers T 1 , T 2 , T 3 , of nearest, next‐nearest and third neighbors are selected. The maximum T i values are 2 2 2 (1D row), 6 6 6 (2D hexagonal net) and 12 6 24 (3D cubic close‐packing). Reduced T 1 or T 2 values for A x B y can be related with attractive or repulsive A–A (or B–B) interactions. A single set of T 1 T 2 T 3 ; y/x values was obtained for y/x = 1–4 and 6. The y/x = 2 structures of three equivalent positions A, B and C are unfavourable for A = ⊕ and B = ⊖ charge or direction of magnetic moments. The spatial distribution of positive and negative potential near A + and B − positions gives rise to neutral C positions. Frustrated magnetic moments at C positions are disordered. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)