Microscopic investigation of shear in multiwalled nanotube deformation

The cylindrical geometry of nanotubes dictates a strong anisotropy of their physical properties. In practice, the difficulty in extracting individual components of the elastic tensor has limited the available information to only very partial and indirect experimental data. Here, the interlayer shear (sliding) modulus (C-44) of single multiwalled WS2 nanotubes was studied by atomic force microscopy bending tests. The observed value of 2 GPa agrees well with the value of 4 GPa obtained for density functional tight binding calculations for 2H-MoS2. This value of the shear modulus represents a much higher degree of anisotropy than that obtained for carbon nanotubes and enables assignment of the mode of shear deformation.