兰州大学机构库 >物理科学与技术学院
碳纳米管与过渡金属原子团簇相互作用的第一性原理研究
Alternative TitleThe study of the interaction between carbon nanotubes and transition metal clusters by first-principles calculation
袁士俊
Thesis Advisor李发伸
2007-05-10
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword碳纳米管 过渡金属团簇 第一性原理
Abstract

碳纳米管(CNT)自1991年被Iijima教授发现,在十多年的时间里在固体物理、分子物理和化学等众多领域都得到了广泛的研究。吸引人们研究这样一种结构简单、仅含单一元素的材料源于碳纳米管具有优良的力学性质,同时它的电学性质随着手征性的不同而表现出半导体、导体甚至超导体等丰富的特性。这些性质使得碳纳米管作为一种纳米尺度的材料在开发新型微电子器件、新型高强度纳米材料方面具有广泛的应用前景。然而实际在碳纳米管的制备和纯化等后期处理的过程中,不可避免的将引入缺陷和吸附杂质。随后人们发现可以通过有意引入杂质来调节碳纳米管的性质,这大大的拓展了碳纳米管的应用范围。引入的杂质可以是有机物、生物大分子,也可以是无机物。其中一类重要的掺杂为纳米尺度的金属团簇。这样的纳米金属团簇本身就由于量子效应使得其具有不同于块体的电学和磁学特性。尤其是3$d$过渡金属在磁性,电性上更具有丰富的物理性质,而且在催化等领域有重要的实用价值。已有大量的实验和理论工作表明,缺陷和杂质对于碳管的性质有重要的调制。所以我们认为结合碳纳米管和过渡金属的纳米团簇这两个研究热点的模拟计算工作将是非常有意义的。 在本论文的工作中,我们利用第一原理计算方法,研究了有缺陷碳纳米管和金属团簇掺杂碳纳米管的模拟计算。主要内容分为三个部分: (1)研究了不同缺陷浓度和不同缺陷类型下金属性碳管的力学性质。通过对比不同缺陷形态碳纳米管的杨氏模量,分析了纳米尺度下缺陷对碳纳米管力学性能的影响。并进一步研究了缺陷碳管的电学磁学性质。(2)在对Fe$_4$团簇的几何构型,电、磁学性质详细研究的基础上,我们进一步研究了Fe$_4$团簇吸附在碳管内壁外壁的复合结构,得到了多种亚稳态;并通过结合能的比较得到了基态结构。分析了Fe$_4$团簇和碳管之间的相互作用,发现Fe-C,Fe-Fe这两种竞争的效应共同决定了Fe$_4$的构型。提出了碳管可以作为约束纳米金属团簇的可控模板的构想。计算得出了“Fe$_4$+CNT”复合体系的电子结构和磁学性质,发现Fe团簇吸附在内外壁的不同效果。进而研究了“Fe$_4$+CNT”复合体系的力学性质,和随之带来的此复合体系的电学,磁性的变化。 (3)作为对比,我们研究了Fe$_4$团簇在单层石墨上的吸附的稳定构型。对比Fe$_4$团簇在石墨和碳纳米管内外壁的吸附情况,总结了吸附结合能及磁矩随C-C网络曲率的变化规律。 总之,在本论文中我们较系统的研究了引入空位缺陷后碳管的性质,和Fe$_4$这样一种过渡金属纳米团簇杂质掺杂后碳管的力学,电学和磁学性质。我们的计算结果预测了碳管对吸附其上金属原子团簇的约束作用。一方面加深了我们对纳米尺度材料之间相互作用的理解,对于设计“Fe团簇+碳管”这样一种具有易操作性和高自旋极化的自旋电学器件提供了理论支持。 更进一步的,基于过渡金属丰富的性质,我们预测“过渡金属团簇+碳管”的设计方案是一类富有潜力的纳米器件模型,进一步的研究仍在进行之中。

Other Abstract

 Carbon nanotube considered as a novel nano-material has been paidmuch attention during the last decade. Owing to their unique quasi-one-dimensional atomic structure and superb mechanical and electronic properties, the single-walled carbon nanotubes (SWNTs) has been playing a significant role in emerging nanotechnology and becoming the important building blocks for nanoelectronic applications, chemical and biological sensing, and nano-composites.However in reality, vacancy defects can appear in CNTs during growing process, purification or irradiation. Some recent experiments indicate the effect of defects can''''''''t be neglected. The defects in CNTs may not only influence the mechanical properties but the electronic, magnetic and chemical characteristics. In the same time, many experiments and theory calculations show the 3$d$ transition metal (TM) atomic clusters have larger magnetic moment than bulk. Despite of purification there are catalytic cluster can remaining on the tip ends or the tube-wall of carbon nanotubes, and metal clusters can be intentionally coated outside of nanotubes. As typical magnetic transition metal and frequently used catalyst in the growing process of carbon nanotubes, Fe filled in or adsorbed on CNTs has been therefore the subjects of many theoretical and experimental studies. The SWNT with periodic carbon-carbon networks has its specific electronic properties, and in the same time, the magnetic metal cluster as impurity can adjust the electronic properties of the compound by inducting the notable difference between the majority and minority densities of states near the Fermi level. These imply that the compound system of magnetic atomic cluster and SWNTs should lead to an even more diverse range of applications. Understanding the interaction between the magnetic cluster and SWNTs should be the kernel of the whole design. In this thesis, we performed the calculation with a DFT-based spin-polarized first-principles method and the main results and conclusion are summarized as follow: (1) The mechanical, electronic and magnetic properties of the carbon nanotubes with different concentrations of vacancy defects have been investigated. Comparing the carbon nanotube with different defects concentrations and different styles, the infection of mechanical properties of carbon nanotube were quantitative analysed. Then the electronic and magnetic properties changes show the effect of vacancy defect is remarkable. (2) Based on the study of Fe4 cluster confined in SWNT the interaction between the metal nanoparticle and SWNT, the interaction between the metal nanoparticle and SWNT was discussed in detail. (3)The Fe4  cluster adsorbed on graphene was also investigated.The tetrahedral struture is still the most stable configuration.

In summary, we consider that the study on the SWNTs with vacancy defencts is practical subject for nano-mechanical, and the interaction between the carbon nanotube and metal nanopartical is an important, intersting and challenging research field. Our study suggests that the carbon nanotube can be further exploited as a template or regulator for the design in the ongoing project.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/229304
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
袁士俊. 碳纳米管与过渡金属原子团簇相互作用的第一性原理研究[D]. 兰州. 兰州大学,2007.
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