Figure shows the relationship between phonon band centers and vacancy migration barriers for all materials considered in this work. To ensure consistent comparisons among the four classes of materials, only vacancy migration barriers are considered. For anti-perovskite materials, the dumbbell migration mechanism is associated with lower barriers, though the formation of the associated interstitial defects is likely less thermodynamically favorable than the formation of vacancies. Two alternative band center metrics considered in previous studies were also assessed here. The mean frequency of modes only at the Γ point of the Brillouin zone was calculated for each material, as was done in ref 73. No correlation was observed between this metric and migration barriers (R 2 = 0.00, Figure ). Band centers were also calculated from the density of states projected onto only the migrating metal cations, which have been reported