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.

Different configurations of a single nitrogen atom adsorbed at different sites on the sidewall of single-walled carbon nanotubes (SWNT's) are studied through first-principles calculations. It is found that the outer surface of the tube wall is reactive to the nitrogen atom, and a nitrogen atom can be chemically adsorbed on it forming an exohedral complex with a binding energy of; 3.86eV for a (5,5) SWNT. Although the inner surface of the tube wall is less reactive than the outer surface, a nitrogen atom can still be adsorbed on the inner wall of the (5,5) tube forming an endohedral complex with the binding energy on the order of ～1.78eV. The local structure of the SWNT around the adsorption sites is substantially changed. From studying the binding energies of a nitrogen atom adsorbed on different armchair tubes (n, n) with n ranging from 5 to 16, it is found that the binding energy for exohedral adsorption decreases significantly with increasing radius (or increasing n) of the tube, while for endohedral adsorption the binding energy varies slightly. The influence of endohedral adsorption of a single nitrogen atom on the local density of states of a (5,5) SWNT is also discussed.

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.