With molecular dynamics(MD) method,axial compression of both perfect and defective armchair(7,7) single-walled BN nanotubes is simulated.Tersoff potential is used to simulate interaction among atoms.To verify the method,armchair(7,7) single-walled carbon nanotubes are calculated.It shows that compressive failure mode of BN nanotubes is almost the same of carbon nanotubes,in which locally-buckling on walls are observed.It is revealed that compressive strength of nanotubes,such as critical axial load,is related to applied strain rate and is affected by temperature especially at low temperatures.However,elastic deformation of nanotubes is not affected by strain rate.It is found that vacancy defects are quite harmful to mechanical properties.Compared with perfect nanotubes,compressive axial strength of defective nanotubes is not affected by temperature significantly.

Left kink (LK) and right kink (RK) migration and velocity at different temperatures and shear stresses are obtained with molecular dynamics (MD) method. By means of nudged elastic band method (NEB) based on tight binding (TB) potential, migration energies of LK and RK are calculated. It shows that due to high migration energy a single LK or RK moves slowly. Multiple kink pair structure of LK and RK-reconstruction defect (RC) dissociated from RK accelerate motion of LK and RK. Particularly, RC makes 30° partial dislocation move faster.