C2HN FRAGMENTS ON METAL-SURFACES

The chemisorption of an acetylene (HCCH), a vinylidene (CCH//2), and an ethylidyne (CCH//3) on metal surfaces, especially Pt(111), is analyzed in some detail, with an emphasis on the electronic rearrangements ensuing. The bonding is described in terms of semilocalized states, in turn obtained via a deconvolution of the total density of states into fragment orbitals of the hydrocarbon and the surface. The geometrical choices made by the various fragments on surfaces are analyzed by simple perturbation theory. It is found that in general the bonding within both the hydrocarbon fragment and the surface is dramatically weakened, as indicated by the changes in overlap populations that result.