The molecular dynamics method was used here to investigate the effect of vacancy defects on the elastic properties of armchair and zig-zag single-walled carbon nanotubes. The results showed that the Young’s moduli of armchair (5,5), (10,10) and zig-zag (9,0), (18,0) single-walled carbon nanotubes were 948, 901GPa, and 804, 860GPa, respectively. The armchair and the zig-zag single-walled carbon nanotube Young’s moduli decrease and increase with the increase of the nanotubes’ diameter, respectively. With the increase of the vacancy defect ratio, the Young’s moduli will decrease. When the vacancy defect achieves a certain ratio, there appears a sudden slow-down in the curves of Young’s modulus vs. vacancy defect ratio and a platform emerges. The influence of the bi-vacancy defects on the Young’s moduli of the carbon nanotubes depends on the orientation of the defects. As the number of atoms between the two single-vacancy defects increased, when the defects were located in the direction of the axis, the Young’s modulus decreased to certain value and fluctuates around it; but when the defects were located in the direction of the circumference, the Young’s modulus decreased first, then ascends and finally tends to a constant, and the Young’s moduli will decrease a little with increasing of the distance between the two single vacancies. The reasons were analyzed by considering the features of the bond σ and bond π between the molecules and the theory of the short-range coupling of the electron clouds between two defects as well as the theory of 5-1DB defect formation in the vacancy defects.

Effects of Vacancy Structural Defects on the Elastic Properties of Carbon Nanotubes. J.H.Yuan, Y.M.Cheng, Z.H.Zhang: Acta Physica Sinica, 2009, 58[4], 2578-84