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 x 10(-9) m(2) s(-1) and at 393 K of 6.7 x 10(-9) m(2) s(-1) are in agreement with those of the PFG-NMR measurements. (C) 2002 Elsevier Science B.V. All rights reserved.