Surface segregation in ternary alloys: a BFS study of Ni–Al–Cu 100/surface composition

Atomistic simulations of surface segregation constitute an essential tool in determining the surface composition and structure of binary or higher order alloys. The presence of metastable states, where widely different surface composition profiles are energetically possible, are severe tests for the ability of experimental techniques for accurately determining the composition of the surface. A clear example of such phenomenon is analyzed in this paper, where the Bozzolo–Ferrante– Smith BFS.semiempirical method for alloys is applied to the study of surface composition of Ni-rich Ni–Al–Cu alloys. A wide range of Cu concentration is considered, showing distinct segregation trends characterizing the low-Cu and high-Cu concentration regimes. The existence of metastable states with energy close to that of the ground state is identified and shown to drive the resulting segregation pattern. The results of several Monte CarlorMetropolis simulations are shown, highlighting the role of the initial state used in the simulation and the temperature treatment of the sample. q1999 Elsevier Science B.V. All rights reserved.