We present systematic ab initio calculations for the nearest-neighbor interaction energies of J-I and I-I pairs in Al (J= vacancy (Vac), Cu, Zn; I= Na-Si (3sp), Sc-Ge (3d and 4sp), Y-Sn (4d and 5sp). The calculations are based on the generalized-gradient approximation in density-functional theory and employ the full-potential (FP) Korringa-Kohn-Rostoker Green's function method for point defects, which guarantees the correct embedding of point defects in an otherwise perfect crystals. The fundamental features of the calculated results are summarized: (1) the J-1 interactions in Al are strongly repulsive for I= 3d and 4d series and attractive for I= 4sp and 5sp series, although the strength of interaction increases with the difference of the valence-electron numbers between J and Al (the host atom), respectively, -1, -2, -3 for Zn, Cu, Vac; (2) the I-I interactions are strongly repulsive for I= 3d and 4d series; (3) The magnetism is important for the defect pairs including Cr, Mn, and Fe, reducing significantly the strong repulsion of J-I and I-I in (1) and (2).
