Interstitials stored in {311} or {111} habit planes form rows of interstitial chains elongated in ⟨011⟩ direction. Exploiting the large aspect ratio to treat chains as infinite, first-principles calculations of large computation supercells reveal a unique formation energy trend for each defect, which is closely correlated with its distinct shape. The most energetically favorable structure changes from {311} rodlike defects to Frank loops as the number of interstitials in the defect increases. These results are consistent with transmission electron microscopy studies
