Static and dynamical properties of carbon nanotubes under uniaxial ten
sion have been investigated via quantum and classical simulations. In
strained nanotubes at high temperatures we observe the spontaneous for
mation of double pentagon-heptagon defect pairs. Tubes containing thes
e defects are energetically preferred to uniformly stretched tubes at
strains greater than 5%. These topological defects act as nucleation c
enters for the formation of dislocations in the originally ideal graph
ite network, and they constitute the onset of a plastic deformation of
the carbon nanotube. The mechanism of formation of such defects, thei
r energetics, and transformations are described. [S0163-1829(98)50208-
1].