Influence of force field parameters on computed diffusion coefficients of CO ₂ in LTA-type zeolite

Molecular Dynamics simulations were used to study the diffusion behaviour of carbon dioxide in Linde Type A (LTA) zeolites. The observed concentration dependencies of the self- and transport diffusions are strongly affected by the choice of the force field. Small differences in the force field result in very small differences in the adsorption isotherms, and quite large differences in the loading dependency of the diffusivities. The Relevant Site Model (RSM) is used to describe the loading dependency of diffusion coefficients. In addition, we investigated the influence of extra-framework cations on diffusion. For zeolites without extra-framework cations, the RSM accurately describes the concentration dependency of CO ₂ diffusivities in LTA-type zeolite calculated using different force fields. The preferential siting of the adsorbate molecules is discussed to elucidate the origin of the differences in the concentration dependence of computed diffusivities using different force fields.