English

Abstract

DFT calculations have been performed on the interactions of carbon nanotubes and carbenes, in order to perform a comparative study of the sidewall functionalization of the two classes of nanotubes, i.e. armchair and zigzag. The systematic investigation of cycloaddition of both zigzag and armchair carbon nanotubes with :CX2 (where X = H, F, Cl, Br, I) has been undertaken. The models selected for zigzag and armchair CNT are (10,0) and (6,6), respectively, since they have comparative radii (~8 A). The bond lengths and binding energies of products are analysed in great detail. The band gaps of these non periodic structures are investigated and correlated with the electronic behavior of 'armchair' and 'zigzag' nanotubes. Our results also confirm the previous studies that armchair nanotubes are thermodynamically more stable than zigzag nanotubes. On comparison of armchair carbon nanotubes with zigzag nanotubes, it is found that trends towards carbenic reactivity are the same in both the cases. The dependence of addition of carbenes on the diameter of the carbon nanotubes is also investigated. The models used for nanotubes in this study range from (3,3) to (10,10). Their reactions with :CH2 have been studied with first principles DFT calculations. An attempt to rationalize the diameter effects is made on the basis of the structures of the nanotubes. It seems that diameter dependence of the reactivity is because of different pyramidalization and π-orbital misalignment angles in different carbon nanotubes. This leads to higher local strain for tubes of smaller diameter that can be partially relaxed by sidewall addition.