An Intermolecular Potential for Accurate Description of the Properties of 12-Ring Siliceous Zeolites

The modified Hill-Sauer force field (mHSFF) proposed by Sholl and co-workers for the 8-membered ring (MR) siliceous zeolite has been modified by tuning the θ₀ of ∠Si-O-Si and ∠O-Si-O and partial charges on Si and O to describe the window size of 12 MR siliceous zeolite more accurately. Proper temperature-dependent trend in minimum window size distribution was obtained using our newly proposed force field (aHSFF-G), which was further underpinned by <i>ab initio</i> density functional theory (DFT) calculation using the PBE functional. The average cell parameter computed using aHSFF-G is in better consonance with the experimental data. Simulations in the Parrinello-Rahman formulation (Molecular dynamics simulation) were carried out on siliceous faujasite using mHSFF and aHSFF-G to examine the volume and the lattice parameter variations of the simulation shell. The temperature dependence of volume and thermal expansion coefficient were evaluated as another test of accuracy. The transferability of aHSFF-G was examined on 5 experimentally known 12 MR siliceous zeolites.