Cristian Blanco, Chandra Saravanan, Melissa Allen and Scott M. Auerbach,
``Modeling Benzene Orientational
Randomization in Na-Y Zeolite at Finite Loadings
with Kinetic Monte Carlo and Master Equation Methods,''
J. Chem. Phys. 113, 9778-9787 (2000).
Abstract
We have modeled the orientational dynamics
of benzene in Na-Y zeolite, motivated by the
NMR study of Isfort et al.
at loadings of five benzenes per cage
[Chem. Phys. Lett. 288, 71 (1998)].
We consider guest-guest interactions in two stages: first,
we include only site blocking; next, we consider both
site blocking and nearest-neighbor attractions.
We calculated orientational correlation functions
using kinetic Monte Carlo and also with
a mean field master equation (MFME). Both methods produce
correlation functions exhibiting biexponential decay in time.
Analytically solving the MFME shows that
long-time decay is controlled by a composite of
intracage and cage-to-cage jumps.
The apparent activation energy is greater
than the fundamental cage-to-cage barrier when considering only site blocking,
but is less than the same fundamental barrier when also including
guest-guest attractions. This suggests that
the actual cage-to-cage barrier
is greater than the 40 kJ mol-1 reported by Isfort
et al., which lends credence to previous
simulations of benzene in Na-Y.
Prof SM Auerbach
29 August 2000