Molecular dynamics simulations were carried out on the ductile behavior of single-walled carbon nano-tubes (SWNTs) under tensile stress by moving both ends at constant velocity at high temperature. The (10, 10) armchair-SWNT resulted in plastic elongation through the sequential Stone-Wales (S-W) transformation, and the chirality changed keeping the two indices equal by alternately taking two dislocation directions with Burgers vectors (b) over right arrow = (1, 0) and (0, 1) instead of choosing only one of them toward zigzag-chirality with one index equal to zero. The comparison in the activation and formation energies for the two directions revealed that the torsional strain induced by the preceding S-W sequence was the main cause of this alternating choice. (C) 2011 Elsevier B.V. All rights reserved.