  Neutron irradiation tends to promote disorder in ordered alloys through the
action of the thermal spikes that it generates, while simultaneously
introducing point defects and defect clusters. As they migrate, these point
defects will promote reordering of the alloys, acting against
irradiation-induced disordering. In this study, classical molecular dynamics
and a highly parallel accelerated sampling method are used to study the
reordering kinetics of Ni$_3$Al under the diffusion of self-interstitial atoms
(SIA). By monitoring the order parameter and potential energy from atomistic
simulations, we show that the SIA acts as a reordering agent in Ni$_3$Al. A
mean-field rate theory model of the interstitialcy-based reordering kinetics is
introduced, which reproduces simulation data and predicts reordering at
temperatures as low as 500 K.
