  To accurately predict the mechanical response of materials, especially at
high strain rates, it is important to account for dislocation velocities in
these regimes. Under these extreme conditions, it has been hypothesized that
dislocations can move faster than the speed of sound. However, the presence of
such dislocations remains elusive due to challenges associated with measuring
these experimentally. In this work, molecular dynamics simulations were used to
investigate the dislocation velocities for the basal edge, basal screw,
prismatic edge, and prismatic screw dislocations in Mg in the sub-, trans-, and
supersonic regimes. Our results show that only prismatic edge dislocations
achieve supersonic velocities. Furthermore, this work demonstrates that the
discrepancy between the theoretical limiting velocity and the MD results for Mg
is due to its sensitivity to large hydrostatic stress around the dislocation
core, which was not the case for fcc metals such as Cu.
