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Effect of quantum partial charges on the structure and dynamics of water in single-walled carbon nanotubes

Summary: Effect of quantum partial charges on the structure and dynamics of water
in single-walled carbon nanotubes
Chang Y. Won, Sony Joseph, and N. R. Alurua
Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and
Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
Received 20 March 2006; accepted 26 July 2006; published online 18 September 2006
In this work, using quantum partial charges, computed from 631G**
/B3LYP density functional
theory, in molecular dynamics simulations, we found that water inside 6,6 and 10,0 single-walled
carbon nanotubes with similar diameters but with different chiralities has remarkably different
structural and dynamical properties. Density functional calculations indicate that tubes with
different chiralities have significantly different partial charges at the ends of tubes. The partial
charges at the ends of a 10,0 tube are around 4.5 times higher than those of a 6,6 tube. Molecular
dynamics simulations with the partial charges show different water dipole orientations. In the 10,0
tube, dipole vectors of water molecules at the end of the tube point towards the water reservoir
resulting in the formation of an L defect in the center region. This is not observed in the 6,6 tube
where dipole vectors of all the water molecules inside the tube point towards either the top or the
bottom water reservoir. The water diffusion coefficient is found to increase in the presence of the
partial charges. Water in the partially charged 10,0 tube has a lower diffusion coefficient compared
to that of in the partially charged 6,6 tube. 2006 American Institute of Physics.


Source: Aluru, Narayana R. - Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign


Collections: Engineering; Materials Science