The present work is a comparative study of possible adsorption structures of the conjugated molecule acrylonitrile on Si(001) employing the state of the art pseudopotential method, within a generalized gradient approximation to the density functional theory. In the recent literature it is proposed the interaction of acrylonitrile with Si(001) through a cycloaddition reaction of the cyano group, in competition with the bounding of the two outer atoms of the molecule skeleton with the Si dimer in cross-dimer and cross-trench geometries; between other geometries like which correspond the reaction of the C = C bond with a Si dimer. Starting from a large number of configurations our calculations favor the planar cycloaddition through the terminal N and C atoms on the Si dimer. In this way we explain the electronic and vibrational features obtained experimentally.

In this work we employ the state of the art pseudopotential method, within a generalized gradient approximation to the density functional theory, to investigate the adsorption process of acetonitrile on the silicon surface. Our first-principles calculations indicate that CH3CN adsorbs via a [2+2] cycloaddition reaction through the C<FONT FACE=Symbol>º</FONT>N group with an adsorption energy around 35 kcal/mol, close to the 30 kcal/mol estimated by Tao and co-workers. The electronic structure and the surface states calculated for the adsorbed system are also discussed.