Structure and self-diffusion of water molecules in chabazite:: A molecular dynamics study

Using classical molecular dynamics (MD) simulations, we have studied some structural and diffusive properties of water molecules adsorbed in chabazite. In particular, we have investigated the variation of the self-diffusion coefficient of the water molecules as a function of their concentration and the nature of the hydration shells of the extraframework Ca++ ions with varying concentrations of water. Our study indicates that the well-defined and stable hydration shells of this ion play an important role in the diffusion process. The diffusion anisotropy is computed at T = 600 K. It is compared with theoretical results based on jump, models and qualitatively compared with pulsed field gradient nuclear magnetic resonance (PFG NMR) experiments of a single chabazite crystal at 293 K and with tracer diffusion studies.