Morphology of a columnar stack of coronene molecules encapsulated in a single-walled carbon nanotube

Abstract

The morphology of stacked coronene molecules encapsulated in a single-walled carbon nanotube (SWCNT) is investigated using atomistic simulation. First, the minimum energy configuration of coronene molecules in a SWCNT is sought by means of conjugate gradient (CG) minimization. Secondly, encapsulation of coronene molecules into a SWCNT existing in a coronene atmosphere is simulated by means of molecular dynamics (MD). In both of the simulations, the diameter of the SWCNT ranges from 1.35 to 1.69 nm, and the final configurations of coronene molecules within a SWCNT are examined. In a thin SWCNT, coronene molecules tilt against the radial direction of the SWCNT and slide relative to each other, whereas in a thick SWCNT, they do not tilt but rotate relative to each other. In a SWCNT of the intermediate diameter, they tilt, slide, and rotate. For the SWCNT diameter less than or equal to 1.52 nm, the mean tilt angle of the stacked coronene molecules almost linearly decreases with increasing the diameter, whereas for the diameter above 1.52 nm, it is approximately 0∘. To check the validity of the results, the MD simulations are performed changing the density of the coronene atmosphere and the length of the SWCNT; the results prove to be valid. Finally, the effects of temperature on the mean tilt angle and mean intermolecular distance of stacked coronene molecules are examined by a rather simplified simulation, which shows that both of them increase with increasing temperature.