Grand canonical Monte Carlo and molecular dynamics simulations of capillary condensation and evaporation of water in hydrophilic mesopores

Abstract

ABSTRACTA combination of grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations (GCMD simulations) was performed to investigate the effect of the difference in chemical potential between the pore surface and gas phase on the adsorption and desorption kinetics of water in a hydrophilic mesopore. The chemical potential of water vapour was controlled by the GCMC method and the adsorption/desorption of water to/from a hydrophilic mesopore was simulated by the MD method. The calculation results showed that when the stepwise change in chemical potential of the gas phase was small, the initial rate of adsorption or desorption of water could be well predicted by the kinetic theory of gases. However, the rate greatly varied depending on the transport mechanisms of water in mesopores such as film flow and column flow. On the other hand, when the stepwise change in chemical potential was large, the initial rate was overestimated by the kinetic theory of gases; however, it did not change greatly with time.