Thermomechanical buckling of boron nitride nanotubes using molecular dynamics

Abstract

We study the thermal buckling behavior of precompressed boron-nitride nanotubes (BNNTs) using molecular dynamics simulations with Tersoff interatomic potential. We compute the critical buckling strains at near-zero temperature, and subsequently precompress the nanotubes at a certain fraction of this value followed by temperature ramping. The critical buckling temperature, Tcr, is marked by a sudden decrease of the internal force. We observe that (i) at small to moderate lengths, Tcr is higher for chiral nanotubes than for either armchair or zigzag nanotubes, (ii) Tcr decreases with increasing diameter unlike in thermal disintegration where disintegration temperatures rise with increasing diameter, and (iii) armchair nanotubes have an optimal length for which Tcr is maximum. We qualitatively explain the reasons for each of the findings. Thermomechanical buckling occurs predominantly in two ways depending on the length of the nanotube—while the shorter nanotubes fail by radial instability (shell-like behavior), the longer ones invariably fail due to bending-buckling (rod-like behavior).