Molecular Simulation Study On Difffusion Of Water In Carbon Nanotubes

Carbon nanotubes, having ideal one-dimensional cylinderic channels, is a new kind ofnanomaterials with very broad applications. Due to its unique structure, it has many unusualmechanical, electrical and chemical properties. For these reasons, the research on carbonnanotubes has become more and more active field. In this paper, we have mainly focused onthe dynamic properties and microscopic structures of the water in carbon nanotubes.We have studied the structural and diffusive properties of water in several armchaircarbon nanotubes such as types of (8,8),(9,9),(10,10),(11,11), and (12,12). The main resultsare:(1) under condition of T=300K, water molecules inside (8,8) tubes have clustered asstacks of quadrangles, which repeat the previous results of Alberto Striolo.Under otherconditions, we haven’t found the emergence of other regular structure like hexagon or helix.(2) The radial distribution functions of water in different diameters indicate that thenumber of average hydrogen bond increase with the tube diameter and confinement decreasewith the tube diameter. The number of hydrogen bond changes from2.10for (8,8) type to2.56for (12,12) type, which is near to2.6for bulk water.(3) The calculations of diffusion coefficient have shown that under given temeperature,the diffusion coefficient increase with the diameter of tubes. For the same tube, the diffusioncoefficient of water increases with temperature.