摘要
氢吸附五边形石墨烯的磁性研究
作者：王影
专业：原子与分子物理
指导教师：王晓春副教授
近年来，磁性材料已经被广泛的应用于生产电子器件、机械制造、轨道交通以及我们日常生活的各个领域，成为高新技术产业的基础功能性材料。并且随着科技的进步，各种电子设备和电器元件将会朝着更小、更轻薄、功能涵盖比较全面等方向发展，因而对磁性材料的大小、自身性质优异性的要求也越来越高。为了适应高新技术的发展及新兴市场的需求，对于新型磁性材料的研究，特别是对纳米磁性材料的研究将成为磁性材料研究的重点内容之一。
2015年，王前教授和他的团队通过计算机拟合的方法模拟出一种新型石墨烯结构，五边形石墨烯。由于它自身的机械稳定性、高强度、耐高温等性能，使它在某些领域中可能优于六边形石墨烯材料。纯净的六边形石墨烯材料对外不显磁性，但可以通过使六边形石墨烯结构吸附原子、制造空穴和拓扑缺陷等方式使其具有磁性。那么，对于五边形石墨烯结构我们参照同样的方法来尝试研究其磁学性质。
本文中，首先我们用氢原子吸附在纯净的五边形石墨烯1×1、2×2、3×3和4×4晶胞结构上，并分别得到稳定的吸附结构。然后利用第一性原理和密度泛函理论的方法对这些氢吸附的五边形石墨烯结构进行了磁性计算。结果显示除了氢吸附五边形石墨烯1×1晶胞结构（即氢吸附五边形石墨烯1×1晶胞的无磁吸附结构）对外不显磁性外，其余氢吸附的五边形石墨烯结构对外均显磁性，磁矩都是0.557 μB/cell。并且通过对氢吸附五边形石墨烯2×2、3×3和4×4晶胞结构的态密度曲线进行分析可知，其磁矩的主要来源都是五边形石墨烯结构中C2原子的p态电子。此外，通过提高氢吸附五边形石墨烯1×1晶胞结构中氢
原子的吸附高度，发现得到的新的氢吸附五边形石墨烯1×1晶胞结构对外显示磁性（即氢吸附五边形石墨烯1×1晶胞的显磁吸附结构），并且磁矩大小为0.551 μB/cell。通过对其态密度曲线进行分析发现氢吸附五边形石墨烯1×1晶胞的显磁吸附结构磁矩的主要来源也是五边形石墨烯结构中C2原子的p态电子。随后，我们分别对这五个结构的电荷密度分布进行了研究，发现当氢原子吸附在五边形石墨烯结构上时，五边形石墨烯中的电荷进行了重新分布，其中H原子和
C1原子之间获得很多的电荷，而C2原子则相对获得的电荷较少。我们可以将氢吸附五边形石墨烯1×1晶胞的两个结构看作纳米磁性开关，当提高氢原子的吸附高度时，整个吸附结构就呈现磁性，当压低氢原子的吸附高度时，整个吸附结构对外不显磁性。并且氢吸附五边形石墨烯1×1晶胞的显磁吸附结构也可以称为氢吸附五边形石墨烯结构能产生较大磁矩的最小结构单元。最后，我们通过对氢吸附五
边形石墨烯1×1晶胞的两个结构之间的过渡路径的计算可知两个结构之间相互转换只需要很少的能量便可完成，由此可见这个纳米磁性开关是可能实现的，并有望广泛地应用于航空航天以及军事等领域。
关于竹子的古诗
关键词：
第一性原理计算，五边形石墨烯，氢原子，磁性，纳米材料
冰淇淋图片真实Abstract
提琴曲The magnetic properties of hydrogenated penta-graphene by剑灵刺客
theoretical study
别有滋味Author：Wang Ying
Major: Atomic and Molecular Physics
洗浴中心设计
Hierophant: Wang Xiao-Chun Associate Professor
In recent years, magnetic materials have been widely ud in all kinds of electronic device productio
n, machinery manufacturing, transportation, and our daily life, which become the basis of functional materials in a high-tech industry. With the development of science and technology, a variety of electronic devices and electrical components will be moved towards smaller, lighter, thinner and multi-functional direction,thus the requirements of size, performance of magnetic material are getting higher and higher. In order to meet the development of high-tech and the needs of emerging markets, the study of new magnetic materials, especially the study of nano-magnetic materials will become one of the key rearches of magnetic materials.
In 2015, Professor Wang et.al simulated a new graphene structure - penta-graphene by computer fitting. It may be superior to graphene in some fields on account of its properties such as mechanical stability, high strength and the high temperature resistance. The pure graphene was not magnetically, but it can be magnetized by making the structure of graphene adsorb atoms, create vacancies and topological defects. Thus, we can study the magnetic properties of penta-graphene with the same method.
In this paper, we first made four penta-graphene 1×1, 2×2, 3×3 and 4×4 cell structures which are absorbed by hydrogen atom, and got the corresponding stable adsorption structures. Then, we calculated the magnetic properties of the hydrogened penta-graphene structures by the First Principl
红肩章e Calculation and the Density Functional Theory. The results show that the 1×1 hydrogened penta-graphene
structures was nonmagnetic（the nonmagnetic adsorption structure of hydrogened penta-graphene）, and the 2×2, 3×3 and 4×4 hydrogened penta-graphene structures have induced magnetism, the magnetic moments of the three structures are all 0.557 μB/cell.
And the main sources of magnetic moments were the p state electrons of C2 atoms in the penta-graphene structure by analyzing the density of state curves of the 2×2, 3×3 and 4×4 structures of the hydrogened penta-graphene. In addition, by increasing the adsorption height of the hydrogen atoms in the 1×1 unit cell structure of the hydrogened penta-graphene, it was found that the new 1×1 hydrogened penta-graphene structure showed magnetism(the magnetic adsorption structure of hydrogened penta-graphene), and the magnetic moment was 0.551 μB/cell. By analyzing the density of state curve, we can find that the main source of magnetic moments for the magnetic adsorption structure of hydrogened penta-graphene was also the p state electron of C2 atoms in the penta-graphene structure. Then, we studied the density of charge distribution of the five structures, respectively. It was found that the charge in the penta-graphene was redistributed when the hydrogen atoms were adsorbed on the penta-graphene structure, in which the H atoms and the C1 a
忘了微笑toms got a lot of charge between the atoms, while the C2 atoms got relatively less charge. The two 1×1 hydrogened penta-graphene structures can be regarded as a nano-magnetic switch, and the entire adsorption structure showed the magnetism when increasing the adsorption height of hydrogen atoms, while it showed no magnetic property when decreasing the adsorption height of hydrogen atoms. Besides, the magnetic adsorption structure of 1×1 hydrogened penta-graphene can also be called the smallest structural of hydrogened penta-graphene structures which could produce the largest magnetic moment. Finally, we calculated the potential barrier between the two structures of the 1×1 hydrogened penta-graphene, the results showed that the transition between the two structures required only a small energy. Thus it can be en that the nano-magnetic switch may be realized, and it can be widely ud in aerospace and military and other fields.
Key Words:
First-principle calculation, Penta-graphene, Hydrogen atom, Magnetism, Nano-materials
