Rich Phase Behaviors of One-Dimensional Interfacial Water via Tuning Interfacial Water-Solid Interaction

Despite numerous studies of water structures at the two-dimensional water-solid interfaces, much less is known about the phase behaviors of water at the one-dimensional (1D) liquid-solid interface. In this work, the 1D interfacial water phase behavior on the outer surface of carbon nanotube-like (CNT-like) models is studied by tuning the Lennard-Jones potential parameter ε of the surface atoms at various temperatures. Extensive molecular dynamics simulations show that ice nanotubes (INTs) can be spontaneously formed on CNT-like model surfaces without nanoconfinement. INTs with flat-square walls (INTs-FSW) are formed on the CNT-like model surface when the ε value is beyond a critical value ε. The value of ε exponentially increases as temperature rises. Contrary to the prevailing formation of INTs-FSW at a relatively strong water-surface interaction, INTs with bilayer hexagonal walls are formed at a weak interfacial interaction with the ε value being in a modest range. An ε-T phase diagram is constructed for the 1D interfacial water on the CNT(100, 0) model surface. Rich phases of H₂O are given in different regions of the phase diagram, depending on the water-surface interaction. This comprehensive study not only provides new insight into the phase behavior of 1D interfacial water but also can guide future experiments to produce INTs without nanoconfinement.