Dislocation theory and molecular dynamics simulations were used to identify possible dislocation dipoles (5|7|7|5, 4|8|8|4) as defect nuclei in nanotubes under tension. The formation energies of the dipoles were evaluated by means of ab initio gradient-corrected density functional theory. The 5|7|7|5 dipole appeared to be more favorable, in spite of its same-element B-B and N-N bonds. When compared with C nanotubes, the formation energy of the primary defect was found to be 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.Dumitrica, G.E.Scuseria, B.I.Yakobson: Physical Review B, 2002, 65[4], 041406 (4pp)