Segregation of copper to the surface of copper-nickel alloys

Copper segregation profiles at the surfaces of ${\mathrm{Cu}}_{17}$ ${\mathrm{Ni}}_{83}$(111) and ${\mathrm{Cu}}_{17}$ ${\mathrm{Ni}}_{83}$(100) have been calculated by a semiempirical procedure based upon previously published data. These profiles indicate that surface enrichment of copper is not limited only to the topmost layer but occurs for several layers away from the surface as well. A comparison of the calculated segregation profiles based upon the experimental results for the (100) and (111) surfaces of ${\mathrm{Cu}}_{17}$ ${\mathrm{Ni}}_{83}$ do not agree with predictions based upon thermodynamic models of segregation.