Metastable water behavior in narrow carbon nanochannel

The water in confined space is still one unclear issue due to the limitations of experimental technique. In this work, the metadynamics (MetaD) simulation method was used to systematically investigate the water behavior confined in hydrophobic nanochannel (carbon nanotube, CNT and carbon nanocone, CNC). We find the phase transition of water is more susceptible to occurring in carbon channel compared to that between graphene plates. The water under hydrophobic nanoconfinement becomes metastable due to the competition between bulk and surface energy, which will lead to a cavitation as the channel size continues decreasing. It shows there exits one critical diameter, under which the water prefers to spontaneously cavitate in CNT. As the apex angle of CNC increases, its tendency varies from being wet to being dry caused by the different dewetting free energy cost. Due to the influence of water thermal motion, as the CNT operating temperature increase, CNT is more inclined to be wet accordingly. The findings in this work can contribute to the understanding of metastable water behavior in hydrophobic nanochannel and the design of innovative CNT/CNC device.