Drastic changes for segregation and wetting between flat and vicinal surfaces of binary alloys

Segregation for the (3 1 0) surface in Cu(Ag) solid solution is studied by Monte Carlo simulations in conjunction with an N-body interatomic potential. Three stages occur according to the bulk concentration of Ag. At low concentration, only the surface plane is enriched by Ag atoms and no structural change is observed. In a second stage, three Ag planes form at the surface. These planes are strongly disordered due to the large size-mismatch between Ag and Cu atoms. Finally, a third stage occurs, in which a thick Ag film grows at the surface. This wetting behaviour is accompanied by a structural change, the Ag film becoming well ordered and growing along the 〈1 1 2〉 direction. Comparison is drawn up with segregation for the flat (0 0 1) surface on one hand and for the Σ=5(3 1 0)〈0 0 1〉 tilt grain boundary on the other hand.