Role of local structure in the enhanced dynamics of deformed polymer glasses

External stress can accelerate the molecular mobility of polymer glasses by several orders of magnitude. The changes in polymer dynamics are commonly interpreted through the Eyring model, which invokes an empirical activation volume whose origin remains poorly understood. In this study, we performed molecular dynamics simulations for polymer glasses under a series of constant stresses and propose an extension of the Eyring model with a machine-learned structural field, softness. Our model connects the activation volume, which is believed to be an empirical parameter, to a structural property (softness) for the first time. We show that stress has a heterogeneous effect on the dynamical enhancement, which depends on local structure. Our model explains the narrower distribution of relaxation time and decrease of dynamical heterogeneity in glasses under creep deformation, which has been observed in previous experiments and simulations. Finally, our results also suggest there is a threshold stress after which dynamical enhancement grows exponentially with stress.