Scott M. Auerbach and Horia I. Metiu,
``Modeling orientational randomization in zeolites:
A new probe of intracage motion, diffusion and cation disorder,''
J. Chem. Phys. 106, 2893-2905 (1997).
Abstract
We have performed kinetic Monte Carlo simulations of benzene
orientational randomization (BOR) and diffusion in Na-Y zeolite for various
Na(II) occupancies and Na(II) spatial patterns. Full
Na(II) occupancy gives BOR rates controlled by intracage motion,
whereas half Na(II) occupancy gives BOR rates
sensitive to both intracage and intercage motion, but insensitive
to particular Na(II) spatial patterns. Alternatively, BOR with one
quarter Na(II) occupancy demonstrates
qualitative sensitivity to different
Na(II) spatial patterns.
Calculated diffusion coefficients vary weakly
with decreasing Na(II) occupancy until ca. one Na(II) per
supercage. Diffusion
coefficients and mean square displacements reveal no information
about intracage motion, and are insensitive to different spatial
patterns of Na(II) cations.
Our computational results thus suggest that measuring
orientational randomization in zeolites can provide important
information regarding intracage motion, diffusion and cation disorder.
Prof SM Auerbach
29 August 2000