Superionic conductors have great potential as solid-stateelectrolytes,but the physics of type-II superionic transitions remains elusive.In this study, we employed molecular dynamics simulations, using machinelearning force fields, to investigate the type-II superionic phasetransition in & alpha;-Li3N. We characterized Li3N above and below the superionic phase transition by calculatingthe heat capacity, Li+ ion self-diffusion coefficient,and Li defect concentrations as functions of temperature. Our findingsindicate that both the Li+ self-diffusion coefficient andLi vacancy concentration follow distinct Arrhenius relationships inthe normal and superionic regimes. The activation energies for self-diffusionand Li vacancy formation decrease by a similar proportion across thesuperionic phase transition. This result suggests that the superionictransition may be driven by a decrease in defect formation energeticsrather than changes in Li transport mechanism. This insight may haveimplications for other type-II superionic materials.