| The discovery of Fullerence and carbon nano-tube accelerates the development of the nano-material science. In the past two decades, the research on carbon nano-material has always been the hot spot of Physics, Chemistry, and Material Science. Recently, the discovery of grapheme becomes a research hot topic again. As an entirely new ideal two dimensional nano-material, single layer graphene has its unique physical and chemical character. It attracted people's attention since it was discovered. Now, people can make single and multi layers graphene through different methods and work on their micro structure and properties by different experimental and theoretical methods. Due to the unique structure and special character of graphite, we can foresee that it will become an excellent material in the further and it will revolutionize the development and application of the electronic device. Therefore, it is important to understand the physical and chemical properties of grapheme ribbon and these jobs is meaningful for realizing its potential and explore new electronic device.Computer simulation is very important in nowadays scientific research. Through simulation, we can not only guide experiment but also get some result which can not be done by experiment and theoretical analysis. Therefore, computer analysis is of great advance in uncovering the inner mechanism of the researched system. It can not be substituted by other methods in the scientific research. Usually, there are two computational methods: empirical or semi-empirical method and ab-initio method. They have their own advantages especially.In this paper, we use empirical method. We build the tight-binding model of single layer graphite according tight binding theory. We analyze the electrical structural of the Zigzag and Armchair single layer graphite. According to this and the Hubbard model, we work on the spin polarization in the Zigzag strip. This paper is divided into two parts: the first part is the foundation of the research; the second part is my own work.(1)Theoretical foundationCalculating single layer graphite by using tight binding model is fast, simple and canbe used in relative large system. We use this method to work on the electrical structureof single layer graphite in this paper. Our group has rich experience on applying tightbinding model to one dimensional polymer. And single layer graphite can beconsidered as a two dimensional structure formed by several polyacetylene. So wecan apply our experiences to the research of the single layer graphite. In the secondchapter, we introduce the model we used and the details of the calculation.(2) The electron structure of two different kinds of graphite stripGraphite strip with different boundary conditions has different electron structure due to it unique honeycomb structure. Actually, there exist two fundamental strip structures: Armchair and Zigzag. It is important to work on these two fundamental structures in order to understand other complex ones. Through the calculation, we prove that there is no band gap for Zigzag structure under the tight binding model. And edge states exist in this system. However, Armchair structure is different: there is no band gap and it is conductor only for 3m -1 width, where m is integral number; for other widths, there is band gap and it is semiconductor. We also notice that the band gap width decreases with the increase of graphite strip width. There is no edge state in Armchair structure.(3) Spin polarization in Zigzag structureRecently, spin polarization has been shown in Zigzag graphite strip through the first principle calculation. This makes spin transport possible in single layer graphite with Zigzag boundary condition. In this article, we use Hubbard model under tight binding condition to calculate the electron magnetic property in Zigzag graphite. It shows that the electron-electron interaction make the spin polarize in Zigzag graphite. At the same time, electron-electron interaction also influences the edge states.
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