  Yielding behavior in amorphous solids has been investigated in computer
simulations employing uniform and cyclic shear deformation. Recent results
characterise yielding as a discontinuous transition, with the degree of
annealing of glasses being a significant parameter. Under uniform shear,
discontinuous changes in stresses at yielding occur in the high annealing
regime, separated from the poor annealing regime in which yielding is gradual.
In cyclic shear simulations, relatively poorly annealed glasses become
progressively better annealed as the yielding point is approached, with a
relatively modest but clear discontinuous change at yielding. To understand
better the role of annealing on yielding characteristics, we perform athermal
quasistaic cyclic shear simulations of glasses prepared with a wide range of
annealing in two qualitatively different systems -- a model of silica (a
network glass), and an atomic binary mixture glass. Two strikingly different
regimes of behavior emerge: Energies of poorly annealed samples evolve towards
a unique threshold energy as the strain amplitude increases, before yielding
takes place. Well annealed samples, in contrast, show no significant energy
change with strain amplitude till they yield, accompanied by discontinuous
energy changes that increase with the degree of annealing. Significantly, the
threshold energy for both systems correspond to dynamical crossover
temperatures associated with changes in the character of the energy landscape
sampled by glass forming liquids. Uniform shear simulations support the
recently discussed scenario of a random critical point separating ductile and
brittle yielding, which our results now associate with dynamical crossover
temperatures in the corresponding liquids.
