Buckling Behaviors of Double-Walled Carbon Nanotubes with Abnormal Interlayer Distances

Several double-walled carbon nanotubes (DWCNTs) composed of internal and external single-walled carbon nanotubes (SWCNTs) with different chirality are presented and simulated by the molecular dynamics (MD) method. Both armchair-armchair and zigzag-zigzag patterns are included. Interlayer distances of the novel DWCNTs are different with 0.34nm of the normal DWCNTs. The interaction between atoms within each tube and the van der Waals force between inner and outer walls are respectively described by the Tersoff-Brenner potential and the Lennard-Jones potential. Firstly, the initial equilibrium structure of each DWCNT is achieved after free relaxation over a long period of time. It should be noted that no any constraint is fixed during the free relaxation process. Then their buckling modes and changes of strain energy under uniaxial compression are simulated to examine the influence of the van der Waals force on the mechanical properties of the novel DWCNTs. Numerical results show that the different van der Waals force coming from different interlayer spacing results in different critical buckling strain of the novel DWCNT under uniaxial compression. It is found that the buckling behaviors of armchair-armchair DWCNTs are similar with but not completely the same as those of zigzag-zigzag DWCNTs. The novel DWCNTs whose interlayer spacings are less than 0.34nm exhibit better compressive stability as compared with the normal DWCNT.