Ordering and interactions

Two- and three-dimensional structures AxBy can be characterized by the numbers T1 and T2 of nearest and next-nearest neighbors of the same kind. A small number of structures at the border of the T1, T2 structure map is stabilized by enthalpy compared with an increased number of entropy stabilized structures. The self-coordination numbers Ti correspond to the numbers of contacts for sphere packing and the numbers of openings in some lipid structures. Structures with T1=2 or 3 are potential candidates for polymer chains or dendrimers, respectively.