Impacts of doping cadmium atoms on the mechanical properties of (n,0) zigzag SWCNTs: DFT approach

The elastic constants and elastic modulus of un-doped and Cd-doped (4-6, 0) zigzag SWCNTs with different diameters are studied by density functional theory. This research has three crystal structures: hexagonal, orthorhombic, and triclinic. Besides, all cases have anisotropy features. This work showed that the elastic con-stants (ECs) had positive and negative values. Negative signs of ECs mean that the material has soft's features. The elastic modulus results indicated that the curve value of Young's modulus (Y), shear modulus (G), and bulk modulus (B) fluctuated up-down depending on the un-doped and Cd-doped (n, 0). The correlation between these elastic moduli as a function diameter of un-doped and Cd-doped zigzag SWCNTs is studied. The results show that Voigt's Y increases with increased tube diameter for both un-doped and Cd-doped. Simultaneously, Reuss and Hill's Y fluctuated for both un-doped and Cd-doped. The explanations of G are similar to Y for the curve value of G and the relation between G and tube diameter. The B values of un-doped (4-6, 0) increased with the increased diameter. Besides, the situation of Cd-doped (4-6, 0) is contrary. These results are strongly related to the diameter, n index, un-doped, and Cd-doped.

Automated summary

The elastic constants and elastic modulus of un-doped and Cd-doped (4-6, 0) zigzag SWCNTs with different diameters were investigated using density functional theory. Three crystal structures, hexagonal, orthorhombic, and triclinic, were examined and all cases exhibited anisotropy. The results revealed positive and negative values for the elastic constants (ECs), where negative values indicated soft features. The elastic modulus varied for un-doped and Cd-doped tubes, with Young's modulus (Y), shear modulus (G), and bulk modulus (B) showing fluctuations depending on the tube diameter. The relationship between these elastic moduli and the diameter of un-doped and Cd-doped zigzag SWCNTs was explored, showing that Voigt's Y increased with tube diameter for both un-doped and Cd-doped, while Reuss and Hill's Y fluctuated. Similar trends were observed for G in terms of its curve value and its relation to the tube diameter. The B values of un-doped (4-6, 0) increased with diameter, whereas Cd-doped (4-6, 0) showed the opposite trend. These findings were strongly influenced by the diameter, n index, and presence of doping.