Effects Of Adsorption And Doping On Configurations And Electronic Structure Of Carbon Nanotubes

With excellent physical and chemical properties, carbon nanotubes have rapidly become the worldwide research focus. Carbon nanotube has become one of the most important issues in material filed due to its excellent physical and chemical properties. Metal atom, B and N atoms doped on the carbon nanotubes is an important way to synthesize functionalized carbon materials. Theoretical investigation of the influences of adoped metal, B and N atoms on the geometrical and electricial properties of carbon nanotubes might provide important theoretical supports for the improvement of carbon nanotube, which is also an important basis for the simulation and design of carbon materials.In this work, the Rhodium adsorption behaviors inside and outside the (n, n) single-wall carbon nanotubes were systematically investigated using density functional theory (DFT) method. The culvuate effects and the different structures (armchair, zig-zag, and chiral types) of the SWCNTs on the Rh adsorption behaviors were calculated. Due to the rolling effects of the SWCNT, the electronic density outside are higher than those inside, which leads to the Rh adsorption energies outsided the SWCNT are higher than the inside ones. With the increase of tube diameter, these differences decrease, and are almost the same when the diameter is up to 13.6 A. The different structures of the SWCNTs have a little influence on the adsorption energies when their diameters are similar. Partial density of states (PDOS) and bandstructure analysis indicate that the strong interactions occur between Rh atoms and SWCNTs. Partial electrons of Rh transfer to the SWCNT, which leads to the Rh atom with positive charge, while the SWCNT with negative charge.The adsorption behaviors and electron properties of different metals (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Au, amd Pt) inside and outside the (6, 6)SWCNT were systematically compared using density functional theory method. It is found that outside configurations are more stable than the inside ones except the Co atom. The interactions between the coin metals (Cu, Ag, and Au) and carbon nanotube are relatively weak; while the interatctions of Pt, Ru, and Rh with the SWCNT are very strong. Electronic analysis indicates that the (6,6) carbon nanotube shows different electronic properties with different adsorption metals.B, N, and BN pair doping on the (10,0)SWCNT are one of the most important methods to improve the electrical properties of carbon nanotubes. In this thesis, we systematically studied the optimized configuration, stability and electronic properties of the different doped systems with various doping concentration. It is found that all the optimized configurations are "bamboo-like". B-doped and N-doped carbon tube change to p and n type semiconductor, respectively; while the BN co-doped carbon tube are intrinsic semiconductors.