The Effects On Structure And Conductivity Of Nontraditional Single-Wall-Carbon Nanotubes By Adsorbed Br And K Atoms

SWCNT have attracted extensive attention due to the unique properties. Designing non-traditional nanotubes and modifying the nanotubes could get bran-new SWCNT, it is be helpful for further widening their potential applications. In the thesis, According the principle of lowest energy, designed more excellent3/8non-traditional SWCNTs, for optimizing the structure of K atom and Br atom doped SWCNTs(DSWCNTs) and calculating the total energy and conductivity, the first principles calculations based on the density function theory is used. GGA and PAW are used, All the calculations are carried out using the VASP, as follows:1、Through optimizing the structure of SWCNTs and according to the principle of lowest energy, the non-traditional3/8SWCNTs is designed the, which binding energy is lower than traditional nanotube. The cage unit cell of Oh symmetry formed with24C atoms connect with three-membered ring and octatomic ring, which separated with each other. The unit cell infinite extending form the3/8SWCNTs. Two3/8SWCNTs connected in parallel get the more stabled SWCNTs. 2、Optimizing the geometrical configuration of3/8SWCNTs with Br doped on the different unequivalence sites. Systematic calculating the adsorption energy of Br doped on bridge site, top site and face site. Analyse and compare of the binding energy, the adsorption energy date indicate the most favorable site of Br atom is the face4+6site on the3/8SWCNT, the adsorption energy at the site is the smallest (-2.27eV).The Br atom could enhance the conductivity of SWCNTs.3、By the analyzing the relation between the properties of the3/8SWCNTs and the number of adsorbed Br atom, It can be seen that the adsorption energies per bromine atom addition are different when different number Br atoms adsorbed on the SWCNTs. When the3Br atoms adsorbed on the SWCNTs, the thermodynamic stability and the conductivity are better than others, the DOS are also have significant differences. Compare with the K-doped3/8SWCNTs, the Br adsorbed on the SWCNTs are better in thermodynamic stability and conductivity.4、The effects on structure and conductivity of3/8DSWCNTs (Double-Barrelled single wall Carbon Nanotubes) by adsorbed Br atoms are investigated similar to SWCNTs, it implied the top6is the most stable adsorption site on the outside of the DSWCNTs. Optimizing the geometrical configuration of3/8Br adsorbed on the DSWCNT and study the thermodynamic stability, the study results show that the two Br-doped DSWCNTs is the most stable geometrical configuration. According to the DOS, analysing the conductivity of the Br-doped DSWCNTs, it indicated the conductivity of the Br-doped DSWCNTs is also enhanced significant.5、The adsorption of K atoms on the DSWCNT was investigated. It is found that for the K-adsorbed DSWCNT, the prefer adsorption site is brl. Optimizing the geometrical configuration of3/8K adsorbed on the DSWCNT and study the thermodynamic stability, it implied that the one Br adsorbed on the DSWCNTs is the most stable geometrical configuration. Compare with the conductivity of the pure DSWCNTs, the K adsorbed on the DSWCNTs is more conductive in the densities of states (DOS).