Simulations of water transport through carbon nanotubes: how different water models influence the conduction rate.
The conduction rate of water through (8,8) and (9,9) carbon nanotubes at 300 K and a pressure difference of 220 MPa is investigated using molecular dynamics simulations. The TIP3P, SPC/E, and TIP4P/2005 water models are considered. The pressure-driven flow rate is found to be strongly model dependent for both nanotubes. The fastest model (TIP3P) has a flow rate that is approximately five times faster than the slowest (TIP4P/2005). It is shown that the flow rate is significantly influenced by the structure taken on by the water molecules confined in the nanotube channels. The slower models, TIP4P/2005 and SPC/E, tend to favor stacked ring arrangements, with the molecules of a ring moving together through the nanotube, in what we term a "cluster-by-cluster" conduction mode. Confined TIP3P water has a much weaker tendency to form ring structures, and those that do form are fragile and break apart under flow conditions. This creates a much faster "diffusive" conduction mode where the water molecules mainly move through the tube as individual particles, rather than as components of a larger cluster. Our results demonstrate that water models developed to describe the properties of bulk water can behave very differently in confined situations.
Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
L
L
Liu
Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
G N
GN
Patey
D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D037742:Nanotubes, Carbon; D014867:Water / Q000737:chemistry*; D014872:Water Movements
D037742:Nanotubes, Carbon; D014867:Water