Coarse-grained molecular dynamics simulations of capillary evaporation of water confined in hydrophilic mesopores

ABSTRACT

Non-equilibrium molecular dynamics (MD) simulations were performed to investigate the capillary evaporation of water confined in hydrophilic mesopores. The electrostatics-based (ELBA) coarse-grained water model was employed to calculate the duration of the time-consuming capillary evaporation process. To evaluate the effect of hydrophilicity of mesopores on the capillary evaporation of water, three types of thin films with a cylindrical mesopore were modelled by tuning the interactions between water and wall atoms. Initially, the cylindrical mesopore was filled with water, and evaporation of the water into vacuum was simulated. The calculation results showed that when capillary evaporation occurred, the desorption rate of water was almost constant in a highly hydrophilic mesopore where a stable water layer was formed on the pore surface, whereas the rate decreased with time in a weakly hydrophilic mesopore where the water layer did not remain stable. As time progressed, the water column shortened and then broke up. The number of water molecules in the mesopores decreased exponentially with time. The difference in the hydrophilicity of the mesopores resulted in different relaxation curves of water desorption from the mesopores.

KEYWORDS:

• Non-equilibrium molecular dynamics simulations
• adsorption and desorption
• diffusion
• advection
• kinetics

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Grant-in-Aid for JSPS Fellows Number 26-8748 (K. Yamashita) and the JST-CREST programme ‘Phase Interface Science for Highly Efficient Energy Utilization’.