Abstract
We calculate the crystal field experienced by a single C60 molecule encapsulated in a single‐walled carbon nanotube. We take the icosahedral symmetry of the C60 molecule fully into account by treating it as a cluster of interaction centers. Although we do not distinguish between armchair, zig‐zag and chiral nanotubes since we consider a nanotube as a uniform cylindrical surface density, we can vary the tube radius R T. We observe a flip of the lowest‐energy C60 molecular orientation when increasing the radius: below R T≈6.5 Å, the lowest energy occurs when two pentagons are perpendicular to the nanotube's long axis, while for higher values, an orientation with hexagons perpendicular to the tube's long axis is energetically more favorable. Then, we consider a linear chain of C60 molecules inside a carbon nanotube, all experiencing the crystal field as a confinement potential. We find tube radius‐dependent effects: distinct equilibrium lattice spacings and lattice contractions. We calculate the structure factor and demonstrate the presence of pseudo‐Bragg peaks. Finally, we briefly comment on the calculation of infrared and Raman absorption spectra within the presented framework.
Acknowledgments
We thank P. Launois and D. Lamoen for useful discussions. The present work has been supported by the Bijzonder Onderzoeksfonds, Universiteit Antwerpen (BOF–NOI). B.V. is a research assistant of the Fonds voor Wetenschappelijk Onderzoek‐Vlaanderen.