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.

A model of an ion embedded in jellium is presented. The static charge state of a heavy ion is determined self-consistently. The effective charge of a heavy ion at low velocities is calculated, which is incorporated with the Brandt-Kitagawa effective charge theory to take the velocity dependence of the effective charge into account. The quantal harmonic oscillator model is generalized to calculate the electronic energy loss of heavy ions colliding with a carbon target. The results are compared with available experimental data.

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.

Defect structures of fullerenes and fullerenelike clusters produced by two C60 molecules colliding at different impact parameters and different collision directions in the energy range 50-600eV have been studied using a molecular-dynamics simulation method. The electronic structures around the defects are obtained using a self-consistent-field Hartree-Fock scheme. The results show that the numbers of coordination-number defects obey a magic rule, and the numbers of rings forming the closed cage structure of the fullerene or fullerenelike products can be well described by a modified formula deduced from Euler's theorem. The electronic structures around the defects are substantially changed in comparison with those of the carbon atoms on normal fullerene cages.

The growth process of higher fullerenes through adduction of small carbon clusters and carbon atoms is studied using a molecular-dynamics simulation method. Small clusters, such as C3 and C2, and carbon atoms easily adsorb on the surface of fullerene cages, which have coordination-number defects or topological defects, when they collide at thermal velocities with the fullerenes. Annealing the chemisorption complexes at 3000K, the attached clusters are soon incorporated into the network of the fullerene cages, via a self-assembly growth process. Although the fullerenes grown in this way usually have defects, their ring structures can be described by a formula deduced from Euler's theorem. The energies of the fullerenes remarkably decrease with their increasing size, when they are annealed to their low-lying energy structures.