Electronic Structure And Optical Properties Of Double-walled Carbon Nanotubes

In the past few decades,due to the huge application prospects and excellent physical properties of carbon nanotubes(CNTs),people have conducted extensive and in-depth research on its various properties.Through the nuclear magnetic resonance study of double-walled nanotubes(DWCNTs),it is found that all DWCNTs have the same tendency of metallic properties.On this basis,through density functional theory(DFT)and intermolecular Hückel model(IMH),it is further discovered that the interaction between the inner and outer tubes of DWCNTs leads to electron migration and orbital mixing between the tubes,which lead to the transition of DWCNTs from semiconducting to metallic.Further research shows that the electron transfer between DWCNTs is from the outer tube to the inner tube,and it is found that the transfer of charge has a certain relationship with the tube spacing and chiral indices.In addition,with the continuous improvement of preparation technology,the controllable chirality and mass production of CNTs are completely possible in the future.Therefore,It is quite meaningful to study the effects of tube spacing and chiral indices on the electronic structure and optical properties of DWCNTs and SWCNTs.Based on the first principles,this paper conducts in-depth and comprehensive research on the structural stability,electronic structure and optical properties of three different chirality SWCNTs and DWCNTs.Before studying DWCNTs,SWCNTs was first studied.Studies on structural stability show that,under the same atomic number,the chiral SWCNTs is the most unstable,followed by the zigzag SWCNTs,and finally the armchair SWCNTs.Research on the electronic structure shows that compared with the tight-binding model,DFT has some new discoveries about its electronic structure after considering the curvature effect.For the study of DWCNTs,the relationship between DWCNTs and its sub-tubes was studied through energy per atom,and the study showed that the interaction between the tubes would reduce the structural stability of the DWCNTs with different chirality.Research on the electronic structure of DWCNTs shows that the DWCNTs with different chirality show a consistent metallization trend,and the metallization trend of the armchair nanotubes is more significant than that of the zigzag.Further research found that the forms of charge transfer about DWCNTs with different chirality are completely different.Finally,the optical properties of all SWCNTs are studied in detail,and the results show that armchair and zigzag SWCNTs can be divided into two types,A and B.The absorption coefficient and reflection coefficient of type A nanotubes are always greater than those of type B nanotubes.The optical properties of DWCNTs selected in the classification are also different.