SIMPLIFIED DESCRIPTION OF COMPLEX STRUCTURES FROM STACKINGS OF UGP

A simplified description of complex structures is proposed. The method consists in defining a geometrical unit of polyhedra, called UGP. The n, a three-dimensional network is built up from simple stackings of th ese UGP. Cationic sites and additional anionic sites are generated fro m the stacking of UGP. An explicit formulation ''counterions[network]a dditional ions'' summarizes the structure description. This method is applied to numerous structures that involve square antiprisms and can be used for other polyhedra. (C) 1997 Academic Press.