Structure types with different properties

The crystal structures of elements A or organic molecules like CH4 can be characterized by the self-coordination numbers T-1 T-2 T-3 of nearest, next-nearest and third A-A or C-C neighbors (with C atoms as centers of gravity of CH4 molecules). The sphere, layer or rod packings have different densities and can be correlated to the sphere, layer or rod-like habit of single crystals. There are about 500 sets T-1 T-2 T-3 with increased T-i values (aristotypes), which can be derived from the 402 characteristic lattice complexes. Structure types are approximated to the list of lattice complexes. Non-spherical molecules, covalent bonding or electronic effects of atoms like lone electron pairs or Jahn-Teller distortion give rise to deviations. The different atoms of binary and ternary compounds can form a single packing like the bcc sphere packing of different atoms in CsCl and AlMnCu2. The interactions between atoms like the repulsive Cs-Cs or Cl-Cl interactions in CsCl can be derived from structure maps with T-1 T-2 T-3 coordinates. NiAs and Pb(CO3) with layer packings of As or Pb atoms and rod packings of Ni or C atoms are examples with different plate- or rod-like habit of crystals depending on the dominance of A-A or B-B interactions. (C) 2005 Elsevier Ltd. All rights reserved