AU(111) AND PT(111) SURFACE PHASE-BEHAVIOR

We describe our recent X-ray scattering studies of the structure and p hases of the clean Au(111) and Pt(111) surfaces. Below 0.65 of their r espective bulk melting temperatures, the Au(111) surface has a well-or dered chevron reconstruction and the Pt(111) surface is unreconstructe d. Above these temperatures, both surfaces reconstruct to form layers that are isotropically compresses and have only short-range order. Thr oughout their reconstructed phases, the densities of the Au and Pt(111 ) surfaces increase with increasing temperature.