The interactions of self-interstitials with twin boundaries

A new mechanism of adsorption of self-interstitials onto twin boundaries (TB) in face-centred cubic (fcc) metals is identified using molecular dynamics simulations. In this mechanism, self-interstitials are arranged in the twin boundary plane forming a previously unknown kind of self-interstitial cluster. The self-interstitial cluster in the twin boundary is bounded by lines of atoms under high hydrostatic pressure while the pressure inside the cluster is much smaller. The atoms in the middle of the cluster have hcp short range order rather than fcc. However, if a new self-interstitial cluster forms in the middle of a pre-existing one, then the atoms in the middle of the new cluster will have regular twin boundary coordination. As a consequence of the formation of self-interstitial clusters inside each other, TB can be powerful, non-saturating sinks for self-interstitials.