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. © 2013 The Author(s) Published by the Royal Society.