By using dislocation theory and molecular dynamics simulations, possible dislocation dipoles (5|7|7|5 and 4|8|8|4) were identified as defect nuclei under tension in nanotubes. The formation energies of the dipoles were evaluated by using ab initio gradient-corrected density functional theory. The 5|7|7|5 dipole appeared to be more favorable, in spite of its homo-elemental B-B and N-N bonds. When compared with C nanotubes, the formation energy of the primary defect was higher and remained positive at larger strains in BN nanotubes; thus suggesting a greater yield resistance.

Mechanically Induced Defects and Strength of BN Nanotubes. H.F.Bettinger, T.Dumitricǎ, G.E.Scuseria, B.I.Yakobson: Physical Review B, 2002, 65[4], 041406 (4pp)