Water diffusion in zeolite membranes: Molecular dynamics studies on effects of water loading and thermostat

Molecular dynamics simulations were employed to investigate diffusion and structural properties of water molecules confined in one-dimensional zeolites. Several water loadings and thermostatting methods were used, and insight into the effects of these was obtained by comparing diffusion and structural properties. Water diffusion was characterised via mean square displacements (self and collective diffusivities) and radial distribution functions enabled the structural ordering of water for different pore sizes and loadings to be compared. Interestingly at lower loadings, molecules tend to form clusters and move collectively, while at higher loadings, the self-diffusion coefficient in the pores is similar to that in bulk water. The length of the simulation cell was varied to determine the system size effects on the results, and narrow pores were also investigated in order to examine how this affected the effectiveness of water transport through the zeolite. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.