  External stress can accelerate molecular mobility of amorphous solids by
several orders of magnitude. The changes in mobility are commonly interpreted
through the Eyring model, which invokes an empirical activation volume whose
origin remains poorly understood. Here, we analyze constant-stress molecular
dynamics simulations and propose an extension of the Eyring model with a
machine-learned field, softness. Our model connects the activation volume, an
empirical parameter, to a structural property (softness). We show that stress
has an inhomogeneous effect on the mobility that depends on local structure,
which explains the narrower distribution of relaxation time observed under
stress.
