Migration of di- and tri-interstitials in silicon

A comprehensive study on the migration of di- and tri-interstitials in silicon is performed using classical molecular
dynamics simulations with the Stillinger–Weber potential. The initial di- and tri-interstitial configurations with the lowest
formation energies are determined, and then, the defect migration is investigated for temperatures between 800 and
1600 K. The defect diffusivity and the self-diffusion coefficient per defect are calculated. Compared to the mono-interstitial,
the di-interstitial migrates faster, whereas the tri-interstitial diffuses slower. The migration mechanism of the diinterstitial
shows a pronounced dependence on the temperature. Like in the case of the mono-interstitial, the mobility of
the di-interstitial is higher than the mobility of the lattice atoms during the defect diffusion. On the other hand, the triinterstitial
mobility is lower than the corresponding atomic mobility. The implications of the present results for the
analysis of experimental data on defect evolution and migration are discussed.