COORDINATION SEQUENCES OF ZEOLITES REVISITED - ASYMPTOTIC-BEHAVIOR FOR LARGE DISTANCES

The coordination sequences of several zeolite frameworks (faujasite, L inde type-A, KFI, sodalite and analcime) have been obtained by direct counting until at least the 23rd coordination sphere. This allows us t o study the asymptotic behaviour of the number of sites in the ith she ll, N(i), for high values of i. In all cases, N(i) adapts well to a pa rabolic law, N(i) = ai2 + b, as expected for three-dimensional lattice s. The constant a, which ranges from 1.43 for faujasite to 2.40 for an alcime, is typical for each framework, and is directly related to the topological density of these materials. For the faujasite framework, w e find a modulation superimposed on the parabolic dependence, which is associated with the particular connectivity of this structure.