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

Abstract

In this work, using quantum partial charges, computed from 6-31G(**)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.

Structural and dynamical properties of water confined in carbon nanotubes

“…In all simulations, CNT's were electrically neutral and formed by rigid walls. This approach is in agreement with previous works, in particular with Won et al [10]. They have shown that although partial charges are present in carbon atoms at the openings of carbon nanotubes, in the regions far from the ends (such as in an infinite nanotube) the value of electric charges on carbon atoms is nearly zero.…”

Specific distributions of anions and cations of an ionic liquid through confinement between graphene sheets

“…7). These behaviors have been seen in many other simulation studies [42,[53][54][55]. A striking feature from these profiles was similar distribution of the anion and the tail group of the cation.…”

“…5.9) [42] to study the properties of the IL ([emim][BF 4 ]) confined between two graphene sheets. Figure 1a and b show the chemical structures and labeling scheme of the cation and anion of this IL, respectively.…”

Transport properties and induced voltage in the structure of water-filled single-walled boron-nitrogen nanotubes

“…So this water-filled SWCNT structure becomes more stable. Geometry optimization 27 and MD simulations 28 validate that this oriented water chain has the minimum energy. Second, the induced dipole on a BNNT has a reverse orientation with the water dipoles, which attract water single file to be oriented.…”