Benzene adsorption and the encapsulation processes in SiC nanotubes

We have performed a theoretical ab initio study of interaction between benzene molecules and silicon carbide nanotubes (SiCNTs). Two different scenarios have been examined, (1) benzene molecules adsorbed on the SiCNT surface, and (2) benzene molecules encapsulated by SiCNTs. In order to provide a more general picture, for both systems we have considered several geometries and nanotube (NT) chiralities. The calculations were performed by using the density functional theory within the local density approximation. The suitability of such choice has been discussed. In (1), we find that the benzene adsorption on the SiCNT is an exothermic process, with binding energies between 0.3 and 0.4 eV/molecule, and in (2) we obtained binding energies of ∼0.6 eV/molecule, revealing a preference for the benzene encapsulated systems. For both cases, we verify that the SiCNTs are more reactive than the carbon nanotubes (CNTs). There are no chemical bonds at the benzene–SiCNT interface, and in (1) we observe that the benzene molecule is attached to the NT surface mediated by π–π stacking interactions, similar to the benzene–CNT systems. On the other hand, we find that the encapsulation of benzene molecules becomes no longer exothermic for SiCNTs with diameters smaller than ∼9 Å. Further investigations indicate a barrierless process for the benzene encapsulation through an open edge of SiCNT. We find attractive forces of ∼0.4 nN, and there is a dependence on the atomic configuration of the open edge on the nanotube.