Effects of boron nitride impurities on the elastic properties of carbon nanotubes

Abstract

The molecular dynamics method is used in this paper to investigate the effect of boronnitride (BN) impurities on the elastic properties of armchair (5, 5) (10, 10) and zigzag (9,0) (18, 0) single-walled carbon nanotubes (SWCNTs). The results show the Young’s moduliof armchair (5, 5) (10, 10) and zigzag (9, 0) (18, 0) SWCNTs with no impurities to be948 GPa, 901 GPa and 804 GPa, 860 GPa, respectively. When the armchair SWCNTs aredoped with BN, their Young’s modulus decreases slightly. However, an increase in thedoping ratio beyond a certain point does not cause any further reduction in the modulus,which continues to fluctuate at about 800 GPa and 760 GPa, respectively. The zigzagSWCNTs behave somewhat differently. When they are doped with BN, theirYoung’s moduli drop quickly, and then rise as the doping ratio increases until itreaches 100% (i.e. boron nitride nanotubes are formed), at which point the Young’smoduli of the nanotubes are 780 GPa and 835 GPa, respectively, 97% that of thecorresponding pure SWCNTs. The effect of a high ratio of BN on zigzag SWCNTs isthus negligible. The reasons for this phenomenon are analyzed according to thelaw of electron cloud coupling between two atoms, which comes from the localdensity approximation (LDA) and is based on density functional theory (DFT).