Ordering and interactions

Two- and three-dimensional structures A(x)B(y) can be characterized by the numbers T-1 and T-2 of nearest and next-nearest neighbors of the same kind. A small number of structures at the border of the T-1, T-2 structure map i s stabilized by enthalpy compared with an increased number of entropy stabi lized structures. The self-coordination numbers T-i correspond to the numbe rs of contacts for sphere packing and the numbers of openings in some lipid structures. Structures with T-1 = 2 or 3 are potential candidates for poly mer chains or dendrimers, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.