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 11.6Å. For all three types of pairs significant interaction energies are found for orientations along 〈110〉 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 〈100〉.