DRAMATIC BOND STRENGTH ALTERATIONS INDUCED ON A ROUGH-SURFACE BY SMALL SUPERFICIAL METALLIC ISLANDS .1. EFFECT OF ISLAND SIZE AND SHAPE

Islands of different size and shape (square or linear, finite or infinite) are introduced at the FCC positions above a single (100) layer of atoms (one s orbital per atom) in order to represent the roughness of the surface. The extended Hückel method with periodic boundary conditions shows the overlap population between the surface atoms near the islands to be strongly modified. Certain bonds are dramatically weakened, others dramatically strengthened. As immediate consequences the surface is prepared for subsequent restructuring and is activated for heterogeneous catalysis. Depending on the nature of the island (island specificity) and on the band occupancy (metal specificity), a given bond may be catalytically active or not. © 1990 J.C. Baltzer A.G. Scientific Publishing Company.