An interesting question in zeolites, which we have explored by geometric modeling, is whether the global (average) structure permits individual SiO4 units to be perfectly tetrahedral or whether local distortions are inevitable. This is very important because the local structures of pores and cages of zeolites may affect properties like catalytic reactions and diffusion. We found that all real (natural and synthesized) zeolites possess a unique property - ‘flexibility window’ - a range of densities over which the framework structure is in principle perfectible (work started at Arizona State University with Professors M. Thorpe and M. Treacy and Dr. S. Wells). Hypothetical zeolite structures which possess such a window are potential candidates for synthesis. This is a significant criterion when searching among millions of hypothetical structures for candidates for synthesis.
