Narrow Results

The co-adsorption of carbon monoxide and benzene on Co(0001) has been studied using density functional calculations. We used the ordered surface unit cell. A comparison of the co-adsorption with CO and benzene two-dimensional networks is also given. The electronic structure reveals that the CO orbitals interact with benzene and Co layer. Regarding the bonding, the Co–Co overlap population decrease 18% after benzene adsorption and increase a little after CO adsorption with a net 14.6% decrease in the co-adsorption system. The CO–benzene interaction is shown by the changes in the C–O (CO) and C–H (benzene) bonds.

The adsorption of small organic molecules on silicon surfaces has been long a subject of investigations, as it provides the fundamental basis of silicon-based technologies in many fields. Several approaches were used, both theoretical and experimental, on many types of adsorbate-substrate systems aiming at determining preferential sites and geometries of adsorption, stable configurations, transition barriers, adsorption mechanisms, electronic structures among others. The research efforts, though, did not always bring to conclusive arguments and on some systems investigations are still going on following the evolution of the experimental techniques and computational methods. In this review, two case studies are reported: benzene and methanol on Si(100)2$\times$1, i.e. examples of a molecular and a dissociative adsorption. The adsorption of benzene on Si(100)2$\times$1 is still an open case, as it may adsorb in di-$\sigma$ or tetra-$\sigma$ bonded configurations, but contrasting evidences have been reported so far, on which of the two is the most stable one and the debate is still open. The adsorption of methanol is less controversial and it is widely accepted it is dissociative with breakage of the O–H at low coverages. But also in this case, investigations are going on to elucidate the adsorption mechanism.