Water permeation and wavelike density distributions inside narrow nanochannels

When water is confined in narrow nanochannels with appropriate radii, the water molecules form single tiles. Here, the gating of water permeation across such nanochannels under continuous deformations and the pattern of the density distribution of water inside are studied by molecular dynamics simulations. When the number of water molecules inside the channel is close to an integer and half, although there is no clearly wavelike pattern for the water density distribution near the center of the channel, we find that the water density distribution, from the data collected with a fixed number of water molecules inside the nanochannel, still shows a clear wavelike pattern. The behavior for the changes in those wavelike water density distributions is found to be consistent with the, gating of the water permeation with respect to the channel deformation. A simple theoretical model is proposed to exploit the physical origin of the wavelike patterns. We find that the potential barriers at both ends together with the tight hydrogen-bonding network are the main responsibility. These findings indicate that both the gating and wavelike pattern are independent of the length of the nanochannels and are helpful to understand similar phenomena in biological channels and other nanoscale pores.