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Studying On The Electronic Structure And Transmission Characteristics Of Small Fullerenes

Posted on:2012-01-31Degree:DoctorType:Dissertation
Country:ChinaCandidate:X X HuoFull Text:PDF
GTID:1111330338454807Subject:Light Industry Information Technology and Engineering
Abstract/Summary:PDF Full Text Request
The fullerenes are a hot area of carbon research and development in the international arena. The structure of fullerenes is peculiar novel and has many excellent physical and chemical characteristics: superconducting, special magnetic properties, optical conductivity properties, non-linear optical properties, etc. The physical and chemical properties of fullerenes are expected to bring about a breakthrough and the provision of new economic growth point about the study about electronic materials, energy and other areas. The development trend of electronic components is size getting smaller and smaller, the power consumption of a single device required getting smaller and smaller, and the cost getting lower and lower. However, when the device sizes get smaller and smaller, we have to consider the limitations of quantum mechanics. The original micro theory in many areas has expired, new theories and new devices (nano-devices) has also begun to appear, fullerenes because of their unique electronic properties may play an important role, It has become one of the most cutting-edge research topics in today's scientific community that synthesis of fullerene carbon cage molecules, properties and decoration inside and outside the carbon cage. Therefore, research about electronic structure and electronic transmission of fullerene molecules is very necessary. In this paper, I mainly studied the structural stability, special properties, electronic structure and electronic transfer properties of the smaller fullerenes. First, we optimized the studying models with the group B3LYP of DFT according the need of computation models and the actual situation of computer, and obtained the stable style; Then we computed the Vibration spectrum, energy level, energy gap, electronic structure and so on. For further studing the characteristics of the models, the models were embeded metal atoms and obtained metal derivatives. We also studied the characteristics of the metal derivatives. Last, we established the electronic transmission systems. The nonequilibrium Green's function method was adopted to study the electronic transmission probability, I-V curves, conductance of the electronic transmission systems and the DOS of the models. The main structure of the paper as follows:The first chapter mainly expounds the structure characteristics, applications, purification and preparation methods and of fullerenes. Fullerenes are composed of carbon atoms with hollow cage, each carbon atom links with the adjacent three carbon atoms. They are purified and preparated through the arc method (arc put electrification method), graphite laser gasification method (laser evaporation graphite method), flame method (benzene flame combustion method), high-frequency heated evaporation graphite method, solar method (solar heating graphite method) and naphthalene pyrolysis methods. Fullerenes have been widely used in physics, electrochemical, etc.The second chapter introduces the theoretical basis and calculating methods which were using to research in this paper. Main use is density functional theory and non-equilibrium green's function method.The basisnset B3LYP/6 -31G* of density functional theory was used to studied the smallest fullerene C20 in theiry in the chapte 3. The influence of the Nitrogen atoms of doping to the electronic structure and the electronic transmission characteristic of C20 was studied and analyzed. Many results were concluded such as the distribution law of quantum flow in the transmission system.Fullerene C32 with D3 symmetry was resaeched in chapter 4. Basis set was used to calculate the single point, vibration frequency, molecular orbital energy levels and energy gap of C32 molecule. The transmission system with Au (1,1,1) electrodes was established. The non-equilibrium green's function method was used to calculate the influence of the distance between the molecules and electrode to the electronic transmission characteristics, the influence of the door voltage to the molecular conductance. Finally, the influence of Mg and Na atoms embedding on the molecular structure stability, electronic structure and electronic transmission characteristic were calculated. Many results were concluded such as Mg and atoms embedding can enhance not only the molecular structure stability but also the electronic transmission performance.Fullerene C36 with D6d symmetry was reseached in chapter 5. We established four transmissionsystems with Au (1,1,1) electrodes by fixing the left electrode and connecting the right electrodes to different position in C36. Non-equilibrium green's function method was sed to calculating the influence which the different position affected to the electronic transmission characteristics. Finally, the influence of the metal Mg and Na atoms embedding on the molecular structure stability, electronic structure and electronic transmission characteristic were calculated.Non-equilibrium green's function method was used to calculate the electronic structure and electronic transmission characteristics of C40 fullerene with D5d symmetry in chapter 6. It is concluded that the molecular chemical activity is stronger than that of the C60 fullerenes, and C40 has semiconductor features.C50 fulleren with D5h symmetric structure was studied in the Chapter 7. Basis set B3LYP/6-31G * of the DFT was adoped to calculate the molecular electronic structure. Non-equilibrium green's function method was used to caculate the electronic transmission probability curve and voltammetric curve of the electronic transmission system with Au(1,1,1) electrodes. Finally, we studied and analyzed the influence which the metal magnesium, sodium atoms embedding affected on the molecular structure stability, charge distribution, electronic structure and the transmission characteristics.The fullerene C72 with D6d symmetry was studied in chapter 8. Its total energy, molecular orbital level and fermi energy were all computated. The transmission probability curve and voltammetric curve of the transmission system were calculated and analyzed. Finally, the influence of Mg atom embeddin on the molecular structure, electronic structure and the electronic transmission characteristic was calculated and analyzed also. Many results were concluded such as the influence of such as Mg atom embedding decrease mot only the structre stability of the C72 molecle but also the molecular electronic transmission performance.We summarized the work of the paper and discussed the later work in chapter 9.
Keywords/Search Tags:fullerene, metal fullerene derivatives, nano-scale devices, electronic conductivity, conductivity, I-V curves
PDF Full Text Request
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