Ab initio calculations of the interaction between native point defects in silicon

The interaction of neutral interstitial-vacancy, interstitial-interstitial, and vacancy-vacancy pairs in silicon is investigated using ab initio calculations. Large supercells of 216 and 512 atoms are used in order to avoid cell-size effects at defect separations up to 11.6 Å. For all three types of pairs significant interaction energies are found for orientations along 〈1 1 0〉 directions up to the maximum separation investigated. Moreover, a pronounced variation of the interaction energies is observed when changing the direction of the defect pair or the orientation of the defects within the pair. If re-orientation of the defects is allowed, the interactions at all separations investigated are attractive with the exception of the interstitial-interstitial pair oriented along 〈1 0 0〉.