Surface segregation of Ag-Cu-Au trimetallic clusters

Segregation phenomena of Ag-Cu-Au trimetallic clusters with icosahedral structure are investigated by using a Monte Carlo method based on the second-moment approximation of the tight-binding (TB-SMA) potentials. We predict that the Ag atoms segregate to the surface of the Ag-Cu-Au trimetallic icosahedral clusters. The Ag concentrations in the surface layer of the clusters are about 11-29 at.% higher than the overall Ag concentration in all the cases studied. The simulation results also indicate that the Au atoms are mainly distributed in the middle shell and the Cu atoms are located in the center for the 147-, 309-, 561- and 923-atom clusters at 300 K. The segregation phenomena of the Ag, Au and Cu atoms in the Ag-Cu-Au trimetallic clusters are mainly due to the different surface energies of the Ag, Au and Cu atoms. It is found that the size and composition have little effect on the segregation phenomena of Ag, Au and Cu atoms in the Ag-Cu-Au trimetalic cluster.