The activated adsorption of ethylene on atomic-oxygen-covered Ag(100) surface and on an open-type stepedge thereon was studied using
density-functional-theory. On perfect Ag(100), such adsorption results in theformation of an oxametallacycle (OMC), with an activation energy slightly larger than 0.3 eV. We find thatthis activation energy is only weakly
depen
dent on the coverage of on-surface oxygen (for
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1/2 ML),whereas the OMC-surface interaction is substantially reduced at high oxygen coverage. Three types of OMCshave been i
dentified on the (100) surface, which display similar stability, and the transformation betweenthem is facile with activation energies below 0.1 eV. We find that the presence of subsurface oxygen reducesthe activation energy for OMC formation and substantially increases the OMC-surface interaction. Thereactivity of the step edge toward the OMC formation strongly
depends on the local coverage of oxygen. Ourcalculations indicate that the relative stability of the OMC intermediate in ethylene epoxidation reaction isstrongly affected by the coverage and configuration of chemisorbed oxygen.