SURFACE-COMPOSITION OF DILUTE CU-AG ALLOYS - A COMPARISON BETWEEN EXPERIMENT AND MONTE-CARLO MODELING

The equilibrium surface compositions of Cu-0.83 atomic percent (a/o) Ag and Cu-0.61 a/o Ag have been determined by Auger electron spectroscopy over the temperature range 450-600-degrees-C. These alloys show strong segregation of silver to the surface. Surface compositions have also been obtained by Monte Carlo simulations, performed in conjunction with an embedded atom method description of interatomic interactions. The results of the simulations have been interpolated by means of an analytical expression based on the regular solution approximation. Comparisons of the simulated surface compositions with experiment indicate reasonable quantitative agreement between calculated and measured surface compositions, but the temperature dependence of the computed surface composition is weaker than that observed experimentally. Possible reasons for the discrepancies are discussed.