Orientation ofC70molecules in peapods as a function of the nanotube diameter

Abstract

Encapsulated C 70 molecules packed in single-walled carbon nanotubes display different orientations depending on the nanotube radius. We present x-ray scattering data obtained on a powder of nanotubes filled with C 70 molecules. Analytical expressions for calculating the diffraction diagram taking into account fullerene orientations are developed. The comparison between calculations and experiments allows us to conclude that the change from the lying to standing orientation-corresponding to the molecule long axis parallel and perpendicular to the tube axis, respectively-takes place when nanotubes reach a diameter of about 1.42 nm. Energy calculations are performed using a Lennard-Jones ͑6-12͒ potential, leading to a calculated reorientation diameter in good agreement with that determined experimentally.

Anisotropic packing of C70 molecules in carbon nanotubes

“…The transition from lying to standing C 70 molecular orientations is seen to cover the range 6.925 Å Շ R T Շ 7.175 Å. This range agrees well with the transition value of 7.1 Å obtained by recent X-ray scattering experiments [15].…”

“…Minimizing with respect to intermolecular distances ( 1) ( ) n n ζ ζ + -and using the potential model of Ref. [11] one obtains equilibrium intermolecular distances a agreeing very well with the most recent experimental values [15]: a = 11.0 Å (lying) and a = 9.8 Å (standing).…”

“…[15]) to us prior to publication, and H. Kuzmany for pointing out the consequences of our results on DWCNT formation. B.V. is a Postdoctoral Fellow of the Fonds voor Wetenschappelijk Onderzoek -Vlaanderen.…”

X-ray diffraction as a tool for the determination of the structure of double-walled carbon nanotube batches

“…19,20 With the information on the relative position of carbon atoms constitutive of nanotubes' walls being lost, the hypothesis of homogeneous scattering surfaces limits the relevance of our calculations to scattering vectors Q with modulus lower than 2.5 Å −1 . The diffraction profile of a powdered sample is given by the square of the Fourier transform of the spatial configuration of scattering surfaces of the nanotubes, for all relative orientations between the nanotubes and the scattering vector.…”

Structural and Vibrational Properties of C60 and C70 Fullerenes Encapsulating Carbon Nanotubes

“…The predicted phases of C 60 s inside SWCNTs have been experimentally observed by Kholoystov et al HRTEM micrographs [19]. molecules is parallel to the nanotube long axis, and the standing up orientation where the C 70 long axis is perpendicular to the nanotube axis [19,20]. The value of the nanotube diameter beyond which the change from the lying to standing orientation occurs is experimentally estimated to ∼1.42 nm.…”