Coalescence, melting, and mechanical characteristics of carbon nanotube junctions

This study employs classical molecular dynamics (MD) simulations to investigate the formation of single-walled carbon nanotube (SWCNT) T junctions via the melting and coalescence of two individual nanotubes. The simulations focus primarily on the synthesized multiterminals of (5, 5)-(9, 0)-(5, 5) and (5, 5)-(5, 5)-(5, 5) T junctions since these particular T junctions represent two extreme cases. The numerical results indicate that most of the cap-to-wall coalescence pathways identified for the nanotubes consist exclusively of Stone-Wales bond rotations. The thermal stability and melting behavior of the two T junctions are studied. It is found that for thermal treatment at high temperature, the (5, 5)-(9, 0)-(5, 5) T junction is more thermally stable than its (5, 5)-(5, 5)-(5, 5) counterpart since its structural dislocations and topological defects accelerate the onset of melting. The effects of the nanotube diameter and chirality on the mechanical responses of the T junctions under tensile and bending loads are also studied. The bending tests reveal an unexpected nanoplasticity mechanism in the T junction subjected to large bending deformation. This nanoplasticity effect causes the bonding geometry to transform from a graphitic $(s{p}^{2})$ structure to a localized diamondlike $(s{p}^{3})$ structure.