title: Unraveling the perplexing structure of the zeolite SSZ-57.
abstract: Previous high-resolution x-ray powder diffraction and transmission electron microscopy studies of the zeolite SSZ-57 could not fully elucidate the structural basis for its puzzling adsorption behavior, which appears to be intermediate between that of a medium- (10-ring) and a large-pore (12-ring) zeolite. Now by applying advanced crystallographic techniques (structure solution in four-dimensional space and interpretation of three-dimensional diffuse scattering by Monte Carlo simulation) and crystal chemistry considerations to high-quality single-crystal x-ray diffraction data collected on a microcrystal (about 2 micrometers by 2 micrometers by 8 micrometers), we have been able to derive a comprehensive description of its silicate framework structure. The framework is related to that of ZSM-11 but is commensurately modulated along the c axis (P4m2, a = b = 20.091 Å, c = 110.056 Å) to yield a structure with a 12-ring:10-ring ratio of 1:15. Disorder of the 12-rings results in a three-dimensional 10-ring channel system with large isolated pockets. The structure helps to clarify the material's catalytic activity.
authors.affiliation: Laboratory of Crystallography, Eidgenössische Technische Hochschule (ETH) Zurich, CH-8093 Zurich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Baerlocher
authors.forename: Thomas
authors.initials: T
authors.lastname: Weber
authors.forename: Lynne B
authors.initials: LB
authors.lastname: McCusker
authors.forename: Lukas
authors.initials: L
authors.lastname: Palatinus
authors.forename: Stacey I
authors.initials: SI
authors.lastname: Zones