title: Zeolite collapse and polyamorphism.
abstract: The phenomenology of zeolite collapse is outlined, drawing on recent synchrotron x-ray diffraction experiments and computer simulations of low density cage structures like zeolite A and zeolite Y. Attention is drawn to the importance of polyamorphism in destabilizing this type of microporous crystal and its role in order-disorder as well as amorphous-amorphous transitions, together with associated differences in entropy and density between polyamorphic phases and the precursor zeolite. Magic angle spinning NMR and inelastic x-ray scattering are used to highlight changes in structural order and mechanical rigidity between the starting zeolite and the final high density polyamorph. In conclusion, two-level systems detected with inelastic neutron scattering are described and their involvement in dictating the dynamics of the collapse of zeolitic cage structures.
authors.affiliation: Centre for Advanced Functional Materials and Devices, Institute of Mathematical and Physical Sciences, University of Wales, Aberystwyth, Aberystwyth SY23 3BZ, UK.
authors.forename: G Neville
authors.initials: GN
authors.lastname: Greaves
authors.forename: F
authors.initials: F
authors.lastname: Meneau
authors.forename: F
authors.initials: F
authors.lastname: Kargl
authors.forename: D
authors.initials: D
authors.lastname: Ward
authors.forename: P
authors.initials: P
authors.lastname: Holliman
authors.forename: F
authors.initials: F
authors.lastname: Albergamo