Equilibrium structures of water molecules confined inside a multiply-connected carbon nanotube: A molecular dynamics study

The water confinement inside a carbon nanotube (CNT) is a well-known phenomenon and has been a subject of both experimental and theoretical interests. However, only simple CNT structures with cylindrical shapes have been considered for the study. In this talk, we report a classical molecular dynamics study of equilibrium structures of water molecules confined inside a multiply-connected carbon nanotube (MCCNT), where a larger (14, 14) CNT is branched off into two smaller (7, 7) CNT arms and then they merge into one. The arrangements of water molecules in the MCCNT are investigated both in terms of water density and an average number of hydrogen bonds per water molecule. Our results demonstrate that the arrangement transition of water molecules occurs several angstroms ahead of the junction, not at the Y-shaped junction. Since a single chain of water molecules can be formed in the (7, 7) tube, that the oscillation wavelength (~ 2. 5 Å) of the number density of water inside the (7, 7) CNT arms is almost same as the so-called hydrogen bond length (2. 8 Å).