Molecular dynamics simulations were used to study the effect of the curvature-induced static dipole moment of small open-ended single-walled carbon nanotubes immersed in water. This dipole moment generated a non-uniform electric field; changing the energy landscape in the carbon nanotube and altering the water conduction process. The carbon nanotube remained essentially filled with water at all times, whereas intermittent filling was observed when the dipole term was not included. In addition, the dipole moment induced a preferential orientation of the water molecules near to the end regions of the nanotube which, in turn, caused a reorientation of the water chain in the middle of the nanotube. The most prominent feature of this reorientation was an L-defect in the chain of water molecules inside the carbon nanotube. The analysis of water energetics and structural characteristics inside, and in the vicinity of, the carbon nanotube helped to identify the role of the dipole moment and to suggest possible mechanisms for controlled water and proton transport at the nanoscale.

Curvature Induced L-Defects in Water Conduction in Carbon Nanotubes. U.Zimmerli, P.G.Gonnet, J.H.Walther, P.Koumoutsakos: Nano Letters, 2005, 5[6], 1017-22