A Transferable Force Field for Predicting Adsorption and Diffusion of Hydrocarbons and Small Molecules in Silica Zeolites with Coupled-Cluster Accuracy

We present a transferable force field for hydrocarbons (linear and branched olefins and paraffins) and small adsorbates (CO2, O-2, N-2, and H2O) in pure silica zeolites. The fitting procedure is based on adsorbate-adsorbent interaction energies obtained from periodic density functional theory calculations and corrected using coupled-cluster methods applied to small clusters. The fitting approach aims at accurate prediction of both adsorption and diffusion properties by using sets of configurations that sample adsorption sites and intracrystalline hopping transition states. The quality of the force field is assessed for a wide range of adsorbates in zeolites with different topologies, showing good agreement between theoretical predictions and a range of experimental measurements of adsorption and diffusion.