Ising Model of Diffusion in Molecular Sieves

Abstract

We have developed a new analytical theory for activated diffusion in zeolites at finite loadings, including the effect of adsorbate-adsorbate interactions. Excellent qualitative agreement is obtained comparing our new theory to kinetic Monte Carlo simulations. We have applied this theory to benzene diffusion in faujasite, to help resolve discrepancies among different experiments. Our results are in qualitative agreement with pulsed field gradient NMR, and in qualitative disagreement with tracer zerolength column data. [S0031-9007(98)06457-6]

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

“…Techniques to take into account these effects using a simulation approach have been developed by Tunca and Ford 279,280 or using an approximate theory by Auerbach and co-workers. [281][282][283][284] An alternative approach is to assume a distribution of lattice sites in a zeolite and to obtain the hopping rates from fitting to experimental data or to assume certain values and investigate the effect of changes in the hopping rate. These simulations are particularly useful to obtain insight into the mechanism of diffusion.…”

Molecular Simulation of Loading Dependent Slow Diffusion in Confined Systems

“…Conventional methods use a hierarchical approach to compute elementary hopping rates for use in a subsequent KMC scheme to obtain self-diffusion and collective diffusion coefficients [2,3,13,14,18]. Let us consider the class of cage/window-type systems (e.g., methane in LTA) where the barriers are entropical in nature.…”

Diffusion in tight confinement: A lattice-gas cellular automaton approach. II. Transport properties

“…This motivates the search for a further simplification of the atomistic models of micropores, to reach a simpler description of the effective interactions such that they can be easily computed and at the same time able to capture the essential features of the real physical systems. [5][6][7][8] In the paper immediately preceding, denoted as Paper I, we describe in detail a lattice-gas cellular automaton ͑LGCA͒ able to model the properties of species bounded to an adsorbent's surface mainly focusing on the structural equilibrium properties of the model. In the following article we report the results concerning the dynamical properties that can be studied from the model.…”