and Pb1-x Snx Te have been measured by use of the 19F(p, αγ) 16O resonance nuclear reaction at 872.1keV with width F=4.2keV. In order to obtain the true range distribution of implanted fluorine from the experimental excitation yield curve, a convolution calculation method is presented, from which the range distribution parameters such as the average projected range Rp, the projected range straggling △Rp and the skewness of the projected range distribution SK were obtained. These experimental range parameters were compared with those obtained by a theoretical calculation and by use of the TRIM89 program, and shows that for all the materials studied here the experimental Re values agree with the theoretical and the TRIM values very well but the experimental range straggling △Re are larger than those obtained by the theoretical calculation and the TRIM89. This phenomenon may be attributed to the enhanced diffusion during the ion implantation.

Molecular-dynamics simulations were used to investigate the storage capacity of hydrogen in single-walled carbon nanotubes (SWNT's) and the strain of nanotube under the interactions between the stored hydrogen molecules and the SWNT. The storage capacities inside SWNT's increase with the increase of tube diameters. For a SWNT with diameter less than 20 ?, the storage capacity depends strongly on the helicity of a the SWNT. The maximal radial strain of SWNT is in the range of 11%-18%, and depends on the helicity of the SWNT. The maximal strain of armchair SWNT's is less than that of zigzag SWNT's. The tensile strengths of SWNT's decrease with increasing diameters, and approach that of graphite (20 GPa) for larger-diameter tubes.

The growth of narrow single-wall carbon nanotubes through adduction of small carbon clusters is studied using a molecular-dynamics simulation method. Statistical behavior of the growth and defect formation process is analyzed. For C2 dimer colliding onto the side-wall of narrow single-wall nanotubes, it is very easy to get the dimer to be incorporated into the network of the tube during annealing, forming localized topological defects. During long-time annealing at 2300K, thermal fluctuation can cause structural switching among different metastable states and thereby result in energy pulses in the energy vs time curve.

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 stopping power of slow antiparticles penetrating electron gases are evaluated within a scattering theory approach to the energy-loss problem. The required effective scattering potential is obtained from a selfconsistent density-functional calculation. A relationship of the stopping power Sα|Z|b (b is in the range of 0.7-0.9) at low velocities is found, in contrast to the Z2 dependence predicted by the linear-response theory. The diffuse distribution of partial wave contributions of screening electrons in the case of antiparticles is quite different from that for normal particles and is thought to be the main reason for the monotonic increment of the stopping power as a function of |Z|.