Structural analysis of zeolite beta through periodic ab initio simulations of XRD and 29Si and 17O NMR spectra

For large systems containing hundreds of atoms in the unit cell, as usually is observed in the zeolitic materials, the use of periodic ab initio calculations is limited by the requirement of huge computation resources. In this work, by using the primitive unit cell of the zeolite beta crystal, which is 50% smaller than its conventional crystallographic unit cell, we are able to perform periodic ab initio calculations for this system, Contrary to cluster-type calculations, the correct chemical environment of the entire zeolite beta crystal is taken into account, allowing for an accurate determination of this XRD pattern and the NMR spectra of the Si-29 and O-17 nuclei. In particular, we present a complete characterization of the distribution of quadrupole coupling constants (C-q), asymmetry parameter (eta), and isotropic chemical shifts for the delta(Si)(iso) and the delta(O)(iso), which have not yet been investigated experimentally. (C) 2015 Elsevier B.V. All rights reserved.