A molecular dynamics study on the impact of defects and functionalization on the Young modulus of boron-nitride nanotubes

In this article, we examine the Young modulus of (6, m) boron-nitride nanotubes with vacancy and functionalization defects. We employ molecular dynamics simulations using the Parrinello-Rahman approach. To this end, all systems are modeled with a reactive many-body bond order Tersoff potential with parameters due to Matsunaga et a]. [K. Matsunaga, Y. Iwamoto, Molecular dynamics study of atomic structure and diffusion behavior in amorphous silicon nitride containing boron, journal of American Ceramics Society 84(10) (2001) 2213-2219], which is able to accurately describe covalent bonding. We apply external stress to periodically repeated tubes in vacuum and derive stress-strain curves for various tensile loads at standard temperature and pressure. In addition to the Young modulus, we study visualized stress-per-atom snapshots of the simulation runs. Our results show that the decrease in Young modulus with increasing defect concentration is independent of the chirality of the tube for vacancy defects. Also, we observe that functionalization does not weaken the tube. There is even indication of a relative strengthening for armchair types. (C) 2009 Elsevier B.V. All rights reserved.