Investigation of Molecular Selenium ‎Adsorption to the Outer Surface of Single ‎Wall Carbon Nanotubes

   In this study the adsorption of selenium molecule (Se2) on the outer surface of zigzag (5,0), (8,0) and (10,0) carbon nanotubes has been investigated. We examined number adsorbed orientations as well as different adsorption sites on nanotubes. The adsorption energies, equilibrium distances, energy differences between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and interaction angles between nanotubes and selenium molecule have been studied in details. The results showed that the best angle of the selenium molecule with the nanotubes is zero degree. Selenium adsorption on the external surface of zigzag nanotubes increased their electrical conductivity. It is found that an increase in nanotubes diameter leads to an increase in their stability. The adsorption energy values of selenium molecule on the surface of zigzag (5,0) and (8,0) nanotubes was low and negative; therefore this was a physical adsorption and exothermic. Independent to the orientation, the adsorption process of Se2 on (10,0) nanotube showed chemisorption with large charge transfer from nanotube to adsorbed molecule.