Effects of atomic vacancies and temperature on the tensile properties of single-walled MoS 2 nanotubes.

Using molecular dynamics simulations, we study the effects of Mo and S atomic vacancies and different temperatures on the tensile properties of single-walled MoS2 nanotubes through a series of tensile tests. Both armchair and zigzag MoS2 nanotubes under uniaxial tensions show phase transitions. Two types of Mo-S bonds play different roles in this phase transition of MoS2 nanotubes. Moreover, the influences of Mo and S atomic vacancies and temperature on the Young's modulus, ultimate strength and fracture strain of single-walled MoS2 nanotubes are investigated systematically. The results show that Mo and S atomic vacancies have no influence on the Young's modulus of MoS2 nanotubes. However, Mo atomic vacancies result in a significant decrease of ultimate strength and fracture strain of MoS2 nanotubes, while S atomic vacancies have a relatively small influence on the fracture properties of MoS2 nanotubes. With an increase in temperature, the Young's modulus and ultimate strength decrease. When the temperature is higher than 300 K, the fracture is changed from brittle to ductile together with an enhanced fracture strain.