Ab initio potential energy surface and molecular dynamics simulations for the determination of the diffusion coefficient of water in silicalite-1

The silicalite-1/water potential function has been developed using quantum chemical calculations at the Hartree–Fock level using the 6-31G* basis sets. The silicalite-1 crystal structure is represented by three fragments, in which the chemical compositions are O10Si10H20, O30Si22H44 and O35Si29H58. Ab initio calculations have been performed for 1032 fragment–water configurations where water coordinates are generated inside the fragments. The intermolecular silicalite-1/water potentials developed from those data points have been used in the molecular dynamics simulations. The obtained diffusion coefficients at 298 K of 3.3×10−9 m2 s−1 and at 393 K of 6.7×10−9 m2 s−1 are in agreement with those of the PFG-NMR measurements.