Density functional study of acetylene and ethylene adsorption on Ni(111)

Optimized geometries and adsorption energies obtained from non- local density functional calculations are presented for the adsorption of acetylene and ethylene on Ni(111). Two cluster models, Ni-4 and Ni-14, are used. The best adsorption modes are mu-bridging and di-sigma for acetylene and ethylene, respectively. In these orientations the overlap between the adsorbate frontier orbitals and the metal cluster orbitals is important, and the donation and back-donation of electrons are large. The calculations support the picture of strongly distorted adsorbates on the surface