The Electronic Properties Of The Deformed Single-wall Carbon Nanotubes

Nano-size conductors and molecular electronic devices are fabricated since electronic devices are tending to be faster, lower-comsumption, smaller and cheaper. The nano-electronics becomes a cross-subject about material science, quantum chemistry and condensed state physics because the limit of the quantum theory makes the abatement of Moore law. Not only are carbon nanotubes the perfect model to show low-dimensional system, but also have extensive potential applications on the materials science and the nano electronics.This is because unique hollow structure, light and high surface area and high aspect ratio of carbon nanotubes lead to excellent mechanical, thermal, electrical, magnetical and other properties. Some researches about its conductance and electronic properties are necessary due to the fact that single-wall carbon nanotube has relatively simple structure and is the study foundation of the complex carbon nanotubes, whereas some defects, deformations and two-end cap in carbon nanotubes can be produced in some laboratories.Using density fuctional theory based on the first principle combined with non-equilibrium green function technology and adopting Gaussian, VNL softwares, this thesis systematically explores electronics properties, conductances and stabilities of zigzag single-wall carbon nanotubes and single-wall two-end capped nanotubes with bent, twist and tensile deformations, including energy gaps, frontier molecular orbitals, Milliken populations, transmission properties, system total energy. Those results are helpful for the developments and practical preparations of nanotube-based devices.First of all, electronics transmission properties and stabilities analysis of the zigzag single-wall and single-wall two-end capped carbon nanotubes with different bent deformations show that energy gaps become narrower, electronics are more active inside bent compression of carbon nanotubes, transmission capacities are also changed significantly.And the changes of conductances are periodic variations wheras stability is gradually reduced with bent angle increasing since structure transform from bond of C = CtoC≡C. In addition, the transmission performences for two-end capped nanotubes are poorer than opened-type but otherwise stabilities for capped-tpye improved to some extent.Secondly, this paper also has simulated and caculated electronic transmission performances and stabilities for the situation of twist deformation with single-wall zigzag and two-end capped carbon nanotubes.Those results show that energy gaps get narrower, leading to improvement of electronics transfer-capabilities, more active electronics in the end caps of nanotubes but lower stabilities because of the change of bond structure. Moreover, Two-end capped nanotubes which have greater stabilities but the transmission capacities are identical with opened-type.The tensile deformation for different carbon nanotubes have also been simulated and analyzed based on the above discussions of two kinds of deformations, find that although Milliken charges in the end caps of nanotube are more active, the changes of conductances are periodic variations, the energy gaps become wider, and electrical conductivities are weaker.Meanwhile, stabilities are gradually reduced as the tension lengths are increasing. Besides, the transmission capacities of opened nanotubes which have weaker stability are similar with the two-end capped-types.We made conclusions that three different types of deformations have great impacts on electronic structures and transmission performances for zigzag single-wall and single-wall two-end capped carbon nanotubes in this paper. Furthmore, design of two-end capped single-wall nanotubes can't significantly improve the performance, but improve stabilities obviously.