Fast diffusion mechanism of silicon tri-interstitial defects

Molecular dynamics combined with the nudged elastic band method reveals the microscopic self-diffusion process of compact silicon tri-interstitials. Tight-binding molecular dynamics paired with ab initio density functional calculations speed the identification of diffusion mechanisms. The diffusion pathway can be visualized as a five defect-atom object both translating and rotating in a screwlike motion along ⟨111⟩ directions. The density functional theory yields a diffusion constant of 4×10⁻⁵ exp(−0.49 eV∕k_BT) cm²∕s. The low diffusion barrier of the compact tri-interstitial may be important in the growth of ion-implantation-induced extended interstitial defects.