  Structural heterogeneity of amorphous solids present difficult challenges
that stymie the prediction of plastic events, which are intimately connected to
their mechanical behavior. Based on a perturbation analysis of the potential
energy landscape, we derive the atomic nonaffinity as an indicator with
intrinsic orientation, which quantifies the contribution of an individual atom
to the total nonaffine modulus of the system. We find that the atomic
nonaffinity can efficiently characterize the locations of the shear
transformation zones, with a predicative capacity comparable to the best
indicators. More importantly, the atomic nonaffinity, combining the sign of
third order derivative of energy with respect to coordinates, reveals an
intrinsic softest shear orientation. By analyzing the angle between this
orientation and the shear loading direction, it is possible to predict the
protocol-dependent response of plastic events. Employing the new method, the
distribution of orientations of shear transformation zones in a model
two-dimensional amorphous solids can be measured. The resulting plastic events
can be understood from a simple model of independent plastic events occurring
at variously oriented shear transformation zones. These results shed light on
the characterization and prediction of the mechanical response of amorphous
solids.
