Adsorption of benzene on Si(100) from first principles

Adsorption of benzene on the Si(100) surface is studied from first principl es. We find that the most stable configuration is a tetra-sigma-bonded stru cture characterized by one C-C double bond and four C-Si bonds. A similar s tructure: obtained by rotating the benzene molecule by 90 degrees, lies sli ghtly higher in energy. However, rather narrow wells on the potential-energ y surface characterize these adsorption configurations. A benzene molecule impinging on the Si surface is most likely to be adsorbed in one of three d ifferent di-sigma-bonded, metastable structures, characterized by two C-Si bonds, and eventually converts into the lowest-energy configurations. These results are consistent with recent experiments.