Computational study of molecular properties of aggregates of C₆₀ and (16, 0) zigzag nanotube

Molecular properties for two aggregates of C₆₀ and a (16, 0) zigzag nanotube: (a) C₆₀ encapsulated in the nanotube, (b) C₆₀ attached to the outer wall of the nanotube, are studied using the self-consistent charge density-functional tight-binding method with additional dispersion correction. The binding energy for the encapsulated fullerene is -108.3 kcal/mol and for the attached fullerene, only -20.3 kcal/mol. The harmonic vibrational frequencies of the aggregates are found to be almost identical to those obtained for the non-interacting system. Very small extent of the changes upon interaction may pose a challenge to study the aggregated structures using experimental spectroscopic methods.