Diffusion of self-interstitial atoms (SIAs) has been studied in bcc-Fe and fcc-Cu using molecular dynamics and interatomic potentials of different types. The Fe potentials describe SIA configurations of different stability. The temperature dependence of the SIA diffusion mechanisms is qualitatively similar for both potentials. At high temperature the diffusion is three-dimensional via the <110> dumbbell mechanism. The contribution of one-dimensional mechanism via the <111> crowdion increases when temperature decreases. At low temperature (<300K) the diffusion mechanism depends on the stable configuration of the SIA.
In fcc-Cu all the potentials reproduce the same stable configuration, namely the <100> dumbbell. The migration mechanism is mainly a three-dimensional random walk via this dumbbell with small contributions from the <110> crowdion at high temperature and a two-dimensional caging mechanism at low temperature.