  Mechanical behaviors of bulk metallic glasses (BMGs) including heterogeneous
and homogeneous deformation are interpreted by phenomenological shear
transformation zones (STZs) model. Currently, information about STZs, i.e. size
and density, is only extracted by fitting model equation to the data obtained
from macroscopic mechanical tests. This is inadequate since structural features
of STZs theory cannot be assessed. Here, we develop anisotropic pair
distribution function (PDF) method for directly characterizing mechanical
response of deformation defects. Our results reveal the physical picture of
deformation defects in BMGs and also provide direct experimental observation of
a link between mechanical deformation and intrinsic properties of deformation
defects in BMGs.
