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Density, distribution, and orientation of water molecules inside and outside carbon nanotubes
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View: Figures


Image of FIG. 1.
FIG. 1.

Intermolecular force vs oxygen separation distance between two water molecules in an equilibrated simulation of at a temperature of and a pressure of . The gray envelope represents the range of forces predicted at each separation distance. The solid line is the mean force at each distance. Inset: force envelope and mean force at separation distances greater than . At these separations, the force envelope decays as , characteristic of a permanent dipole–permanent dipole interaction. The mean effective force is related to the oxygen-oxygen LJ interactions and decays as .

Image of FIG. 2.
FIG. 2.

(a) Cropped axial snapshot of CNT in water. Full simulation cell side length is . The layering scheme used to analyze water near and within the CNT is also shown. Each layer has a thickness of and is identified using the midpoint radial position . (b) Cropped axial snapshot of CNT in water. Full cubic simulation cell side length is . Both images are to the same scale and all numbers are in nanometers.

Image of FIG. 3.
FIG. 3.

Water density inside and outside each CNT. The density profile in the unconfined water is invariant with CNT diameter and the same as that near a flat graphene sheet. The density profile in the confined water is a function of tube diameter. The innermost layers for the 1.1 and tubes are at and . Guidelines are added to highlight the minima and maxima.

Image of FIG. 4.
FIG. 4.

[(a)–(c)] Molecular distribution at , , and for the 6.9, 2.8, and CNTs. The mass distribution at is similar for all tubes. For the CNT, this same pattern is present at both and . The distribution at for the 6.9, 2.8, and CNTs becomes more uniform with decreasing CNT diameter. In frame (c), the detailed view identifies the circumferentially aligned (C) and axially aligned carbon atoms (A and ) that form the six-atom carbon honeycomb. All dimensions are in nanometers.

Image of FIG. 5.
FIG. 5.

(a) Orientation distribution spheres at and for the CNT. The projected length of the unit dipole moment vector, as printed in the figure, indicates the degree of rotation out of the plane of the page. Molecules are biased toward either an axially aligned carbon atom (A) or a circumferentially aligned carbon atom (C), as highlighted by the orientation distribution and the three water molecules beside the sphere. (b) Orientation distribution at near the CNT. A single preferred orientation points normal to (in or out of) the page. (c) Distribution at near the CNT. The water molecules form a pentagonal structure, resulting in two preferred orientations pointing away from the surface. A third preferred orientation points toward the CNT surface but is unbiased toward any particular axially or circumferentially aligned carbon atom.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Density, distribution, and orientation of water molecules inside and outside carbon nanotubes