Atomistic characterization of chemical element distribution is crucial to understanding the role of alloying elements for strengthening mechanism of superalloy.In the present work,the site preferences of two alloying elements X-Y in γ-Ni of Ni-based superalloy are systematically studied using first-principles calculations with and without spin-polarization.The doping elements X and Y are chosen from the 27 kinds of 3d,4d,5d group transition metals(Sc,Ti,V,Cr,Mn,Fe,Co,Cu,Zn,Y,Zr,Nb,Mo,Tc,Ru,Rh,Pd,Ag,Cd,Hf,Ta,W,Re,Os,Ir,Pt,Au)and Al.We find that the spin-polarized calculations for Re-Re,Re-Ru,Re-Cr,Ru-Cr show a strong chemical binding affinity between the solute elements and are more consistent with the experimental results.The binding energies of pairs between the 28 elements have an obvious periodicity and are closely related the electronic configuration of the elements.When the d-electrons of the element are close to the half full-shell state,two alloying elements possess attractive binding energies,reflecting the effect of the Hunds rule.The combinations of early transition metals(Sc,Ti,V,Y,Zr,Nb,Hf,Ta)have a repulsive interaction in γ-Ni.These results offer insights into the role of alloying elements for strengthening mechanism of superalloy.