Collisions between two C60 molecules are studied using molecular dynamics simulations. The results show that dumbbell-shaped (C60)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 C60 molecules fuse to form one large C120 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 C60 molecule.

The hydrogen-storage behavior of single-wall carbon nanotubes was studied using molecular dynamics simulations and ab initio electronic calculations. Hydrogen atoms with kinetic energy of 16-25eV were observed to penetrate into and be trapped inside the tube. Consecutively injected H atoms form hydrogen molecules, and gradually condense to become liquid hydrogen in the tube. The density of injected hydrogen in the tube and the pressure on the wall of the nanotube induced by the stored hydrogen molecules were evaluated at room temperature.