Single-walled gold nanotubes grown in carbon nanotubes: Molecular dynamics simulations

Using the classical molecular dynamics method, we have investigated the structure and behavior of the confined water in (20, 0) and (19, 0) single-walled carbon nanotubes (SWCNs). It has been found that several kinds of the double-walled ice nanotubes (Ice-NTs) can indeed be obtained, depending on the diameter of confined SWCNs and the axial pressure. Furthermore, a first-order phase transition—a liquid to double-walled Ice-NT occurs for water in the (20, 0) SWCN at 300 MPa with the melting temperature lower than that of the bulk water. It is noted that water molecules in the tube wall present square lattices at lower pressure, and triangular lattices at higher pressure. More interestingly, high-density nano-ice displays regular chiral double-walled Ice-NT within (19, 0) SWCN at 1.2 GPa, and the outer wall can be considered as (11, 3) Ice-NT resembling the gold nanotube.