We report computer simulations of oscillatory athermal quasi-static shear
deformation of dense amorphous samples of a three dimensional model glass
former. A dynamical transition is observed as the amplitude of the deformation
is varied: for large values of the amplitude the system exhibits diffusive
behavior and loss of memory of the initial conditions, whereas localization is
observed for small amplitudes. Our results suggest that the same kind of
transition found in driven colloidal systems is present in the case of
amorphous solids (e.g. metallic glasses). The onset of the transition is shown
to be related to the onset of energy dissipation. Shear banding is observed for
large system sizes, without, however, affecting qualitative aspects of the
transition
