Topological Descriptor for Oxygens in Zeolites. Analysis of Ring Counting in Tetracoordinated Nets

Topology of zeolite nets has been studied in terms of rings. A freely available software tool for the calculation and systematic analysis of the rings in zeolite nets is presented. Ring indices, associated to T (tetrahedral) and O atoms, are defined as a new topological concept. Ring count is also proposed as a topological descriptor of a structure which gives a fingerprint of the rings (number and size) in a zeotype. These topological concepts are linked with chemical descriptors and used together to systematize and characterize useful information on zeolites such as ring occurrence and TOT angles between different structures. Ring indices of O-sites can be employed to characterize the location of protons in acid zeolites giving a structured information on the ring environment of each active site.