Phase-coexistence of a Ag/Pt surface-alloy and a pure Pt-hex reconstructed phase was observed for sub-0.3ML Ag coverage on a Pt(100) surface by scanning tunnelling microscopy and temperature-programmed desorption of Ag. It was argued that, despite a stronger homo-atom interaction, mixing at the surface was observed because the intrinsic tensile stress of the Pt(100) surface facilitated the incorporation of the slightly larger Ag atoms into the surface layer in order to minimize strain energy of the surface. Thus, surface-alloying presents an alternative to surface reconstruction as a means of strain minimization. Therefore, a competition between surface reconstruction and alloying to reduce the stress at the surface exists and, consequently, a two-phase coexistence of an alloy-phase and a pure Pt hex-reconstructed phase were observed.

Silver on Pt(100) - Alloying versus Surface Reconstruction -Two Competing Mechanisms to Reduce Surface Stress. M.Batzill, B.E.Koel: Europhysics Letters, 2003, 64[1], 70-6