手性碳纳米管的微观结构衍生及电子特性

发布时间：2018-04-03 13:48

  本文选题：手性碳纳米管　切入点：核结构　出处：《新疆师范大学》2017年硕士论文

【摘要】：碳纳米管(CNTs)在生物工程、医学载体、储氢材料等方面具有潜在的应用价值,在原子尺度范围内,其结构的变化改变着它的电子特性。为了研究手性碳纳米管的结构特征和电子特性,我们通过建立了“一端开口,一端闭口”的生长模型,采用第一性原理密度泛函理论(DFT),模拟计算了手性碳纳米管核的形貌,研究其衍生过程和电子特性,其中包括单壁(SWCNTs)、双壁(DWCNTs)以及三壁碳纳米管(TWCNTs)。主要研究内容及结论如下:1、微观结构衍生过程解释了如何获得手性碳纳米管,即可以通过逐层吸附d′个碳原子(Cd')。密立根电子转移解释了碳纳米管的生长点位于碳纳米管的开口端,其中,多壁碳纳米管还遵循 由外向里‖的微观结构衍生规律。2、通过结构的稳定性分析说明了随着管径,管间距或管壁的增加,这些开口端,处于亚稳定状态的碳原子占所有碳原子的比例逐渐减小。因此,随着管径,管间距或管壁的增加,碳管状团簇的平均结合能Eb(l)的增长趋势越加不明显。3、通过周期性边界条件(PBC)模拟计算,结果显示了获得的无限长碳纳米管依赖于其对应的核结构。能带结构的分析说明了能隙是由碳管壁的曲率造成的,并且能隙随管径的增大显著地减小。(1)当满足n m≠3q时(对于整数q,n�em),SWCNTs呈现半导体性质;当满足n m=3q时,单壁碳纳米管呈现导体性质;(2)对于(n1,m1)@(n2,m2)型双壁碳纳米管,当满足n1 m1≠3q@n2 m2≠3q嵌套或者n1 m1=3q@n2 m2=3q嵌套时,手性DWCNTs呈现导体性质;当满足n1 m1≠3q@n2 m2=3q嵌套时,手性双壁碳纳米管呈现半导体性质;(3)对于(n1,m1)@(n2,m2)@(n3,m3)型手性TWCNTs,当满足n1 m1≠3q@n2 m2≠3q@n3 m3=3q嵌套或者n1 m1=3q@n2 m2=3q@n3 m3=3q嵌套时,手性三壁碳纳米管就呈现导体性质。我们模拟计算的碳纳米管核结构和微观结构衍生过程更好的阐述了在实验上手性碳纳米管可能的生长机制,并且在工业水平上为手性碳纳米管结构均一可控生产提供有益指导。
[Abstract]:Carbon nanotubes (CNTs) have potential applications in bioengineering, medical carriers, hydrogen storage materials and so on. In the atomic scale, the structural changes of CNTshave changed its electronic properties.In order to study the structural and electronic characteristics of chiral carbon nanotubes, we have established a growth model of "one end open, one end closed". The morphology of chiral carbon nanotubes has been simulated and calculated by first principle density functional theory (DFT).The derivation process and electronic properties were studied, including single-walled SWCNTsO, double-walled DWCNTsand three-walled carbon nanotubes (TWCNTsN).The main research contents and conclusions are as follows: 1. The microstructural derivation process explains how to obtain chiral carbon nanotubes, that is, they can be adsorbed by layer by layer.Millikan electron transfer explained that the growth point of carbon nanotubes was located at the open end of carbon nanotubes, in which multi-walled carbon nanotubes also followed the law of microstructural derivation from extroverted tubes.With the increase of tube spacing or tube wall, the proportion of the carbon atoms in the metastable state to all the carbon atoms decreases gradually.Therefore, with the increase of pipe diameter, tube spacing or tube wall, the increasing trend of the average binding energy of carbon tubular clusters is less obvious, and calculated by PBC (periodic boundary condition).The results show that the obtained infinite carbon nanotubes are dependent on their corresponding nuclear structures.The analysis of the band structure shows that the energy gap is caused by the curvature of the carbon tube wall, and the energy gap decreases significantly with the increase of the diameter of the tube.鍗曞�佺⒊绾崇背绠″憟鐜板�间綋鎬ц川;(2)瀵逛簬(n1,m1)@(n2,m2)鍨嬪弻澹佺⒊绾崇背绠，

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