  We demonstrate that irreversible structural reorganization is not necessary
for the observation of yield behaviour in an amorphous solid. While the
majority of solids strained to their yield point do indeed undergo an
irreversible reorganization, we find a significant fraction of solids exhibit
yield via a reversible strain. We also demonstrate that large instantaneous
strains in excess of the yield stress can result in complete stress relaxation,
a result of the large non-affine motions driven by the applied strain. The
empirical similarity of the dependence of the ratio of stress over strain on
the non-affine mean squared displacement with that for the shear modulus
obtained from quiescent liquid at non-zero temperature supports the proposition
that rigidity depends on the size of the sampled configurational space only,
and is insensitive as to how this space is sampled.
