It was shown, by using first-principles calculations, why the anti-structure pair (GaAs-AsGa) in the nearest-neighbor configuration was not detected experimentally. An energy barrier to concerted exchange was seen to be responsible for recovery of the ideal crystal structure. This explained why, although it was energetically more favorable than the next-nearest neighbor case, the nearest-neighbor anti-structure pair was not observed at room temperature.

Concerted-exchange mechanism for antistructure pair defects in GaAs A.Janotti, A.Fazzio, R.Mota, P.Piquini: Solid State Communications, 1999, 110[8], 457-61