  Large-scale atomistic calculations, using empirical potentials for modeling
semiconductors, have been performed on a stressed system with linear surface
defects like steps. Although the elastic limits of systems with surface defects
remain close to the theoretical strength, the results show that these defects
weaken the atomic structure, initializing plastic deformations, in particular
dislocations. The character of the dislocation nucleated can be predicted
considering both the resolved shear stress related to the applied stress
orientation and the Peierls stress. At low temperature, only glide events in
the shuffle set planes are observed. Then they progressively disappear and are
replaced by amorphization/melting zones at a temperature higher than 900 K.
