RECONSTRUCTION MECHANISM OF FCC TRANSITION-METAL (001) SURFACES

Ab initio studies of the reconstruction mechanism of (001) fcc transit ion metal surfaces are presented, showing that a close-packed quasihex agonal reconstruction is possible for the late 5d metals Ir, Pt, and A u, while it is disfavored in the isovalent 4d metals Rh, Pd, and Ag. T he driving mechanism is identified in the tensile excess stress of the unreconstructed surfaces. The stress overcomes the substrate resistan ce to reconstruction only in 5d metals, where it is much larger than i n 4d metals because of the stronger relativistic effects. The origin o f surface stress is a d charge depletion from the surface layer.