Dimerization and fusion of C-60 molecules caused by molecular collision

Collisions between two C-60 molecules are studied using molecular dynamics simulations. The results show that dumbbell-shaped (C-60)(2) dimers with almost intact cages can be formed at low collision energies, and when the collision energy is high enough to overcome the fusion barrier, the two colliding C-60 molecules fuse to form one large C-120 cluster. These coalescence reactions are found to have very clear threshold behavior. The threshold energy of dimerization is dependent on the classical impact parameter between the mass centers of the colliding partners, and on the collisional orientation. The coalescence reactions are shown to be deep inelastic. The total cross section for the coalescence reaction is estimated to be on the order of the area of a circle, that has a radius equal to the diameter of a C-60 molecule.