Energetics and stability of C₆₀ molecules encapsulated in carbon nanotubes

An energetic analysis was performed to study the interactions of C₆₀ molecules encapsulated in carbon nanotubes. Both direct interaction between C₆₀ molecules through van der Waals forces and indirect interaction between encapsulated C₆₀ molecules through the elastic deformation of their host carbon nanotubes were considered. For C₆₀s encapsulated in a (9, 9) nanotube, the indirect interaction dominates and a relatively large energy barrier exists for the formation of a uniform, stable, one-dimensional (1-D) C₆₀ array. For a (10, 10) nanotube, the indirect interaction leads to a small energy barrier to form a 1-D C₆₀ array, while for a (11, 11) nanotube the influence of the indirect interaction is negligible. Molecular dynamics simulations were performed to confirm the present energetic analysis, suggesting that the indirect interaction between encapsulated molecules/particles through the elastic deformation of their host nanotubes may affect the stability of nanotube-based structures.