title: Rigid, flexible and impossible zeolite and related structures.
abstract: The flexibility or otherwise of periodic tetrahedral TX2 frameworks formed by corner-sharing regular TX4 tetrahedra is discussed. In particular, when T-X-T angle constraints are included, a suitable embedding can often only be found, if at all, in an symmetry less than the maximum possible for that topology. Examples illustrating this are adduced.
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, , Tempe, AZ 85287, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: O'Keeffe
keywords: periodic nets; symmetry; zeolites