本文選題：密度泛函理論 + 缺陷曲率�。� 參考：《內(nèi)蒙古科技大學(xué)》2015年碩士論文

【摘要】：完美的碳納米管具有良好的電子、機械與結(jié)構(gòu)性能。然而，實際中不可避免地引入各種缺陷結(jié)構(gòu)，，如吸附質(zhì)吸附、SW(stone—wales)拓撲缺陷、原子空位缺陷。在這些結(jié)構(gòu)缺失中，原子結(jié)構(gòu)缺失是最多產(chǎn)和重要的結(jié)構(gòu)缺陷，碳納米管中空位的產(chǎn)生對其機械、物理化學(xué)性質(zhì)有極其重要的影響。因此，針對碳納米管原子結(jié)構(gòu)缺陷的問題研究是深入了解其結(jié)構(gòu)和物理化學(xué)性能及解決其在實際應(yīng)用的根本問題之一。 本論文采用密度泛函方法系統(tǒng)地研究了(5,5)椅型管和(n,0)(n=6～10)鋸齒型管單到八空位缺陷(V1～V8)的空位形成能、產(chǎn)物結(jié)構(gòu)、空位結(jié)構(gòu)的穩(wěn)定性隨空位原子數(shù)的變化規(guī)律及其它們隨(n,0)管中n的變化規(guī)律，且主要結(jié)果如下， (1)基于曾提出的方向曲率理論推導(dǎo)了缺陷曲率，并將其應(yīng)用于椅型與鋸齒型單壁碳納米管的V1～V8空位形成能預(yù)測。對一種Vn，空位形成能隨著缺陷曲率的增大而總體呈現(xiàn)減小趨勢，且對椅型碳納米管，原子容易沿著鋸齒形鏈去除；對鋸齒型碳納米管，原子容易沿著椅形鏈去除。此外，產(chǎn)物中缺陷區(qū)的局域結(jié)構(gòu)影響空位形成能的大�。� (2)不管是椅型還是鋸齒型管，每一種Vn中的最小空位形成能隨空位原子數(shù)n值的增大呈奇偶振蕩規(guī)律，且具有偶數(shù)個原子空位的形成能小，奇數(shù)個原子空位對應(yīng)的形成能大； (3)為了探討Vn缺陷的穩(wěn)定性，考慮了兩種解離過程，即Vn→Vn1+V1和2Vn→Vn1+Vn+1，且分別對應(yīng)第一和第二解離能。計算結(jié)果表明，Vn缺陷中的n為偶數(shù)時對應(yīng)的第一和第二解離均大于Vn-1和Vn+1的，即，V2, V4和V6缺陷較穩(wěn)定； (4)對(n,0)鋸齒型單壁碳納米管，每一種Vn中的最小空位形成能管徑的增大整體呈現(xiàn)增大趨勢，且當(n,0)管中的n值為3的倍數(shù)時，由于其能隙最小，這個最小空位形成能比預(yù)期值要小。
[Abstract]:The perfect carbon nanotubes have excellent electronic, mechanical and structural properties. However, it is inevitable to introduce a variety of defect structures, such as adsorbent adsorbent SWS stone-wales topological defect and atomic vacancy defect. Among these structural deletions, atomic structure deletion is the most productive and important structural defect. The generation of vacancies in carbon nanotubes (CNTs) has an extremely important effect on the mechanical, physical and chemical properties of CNTs. Therefore, it is one of the fundamental problems to understand the structure and physicochemical properties of carbon nanotubes (CNTs) and to solve their practical applications. In this paper, the vacancy formation energy and product structure of the zigzag tube with single to eight vacancy defects (V1 / V8) have been systematically studied by using the density functional method (DFT). The stability of the vacancy structure varies with the number of vacancy atoms and the variation of n with the number of vacancies in the tube. The main results are as follows. 1) based on the previously proposed directional curvature theory, the defect curvature is derived and applied to predict the V1~V8 vacancy formation energy of chair and sawtooth single-walled carbon nanotubes. For one type of Vns, the vacancy formation energy decreases with the increase of defect curvature, and for chair carbon nanotubes, atoms are easily removed along the sawtooth chain, and for sawtooth carbon nanotubes, atoms are easily removed along the chair chain. In addition, the local structure of the defect region in the product affects the size of the vacancy formation energy. (2) for both chair and sawtooth tubes, the minimum vacancy formation energy of each type of V _ n oscillates with the increase of the number of vacancy atoms n, and the formation energy of even number of atomic vacancies is small, and the formation energy of odd number of atomic vacancies is large; In order to study the stability of Vn defects, two kinds of dissociation processes are considered, that is, VN Vn1 V1 and 2Vn Vn1 VN1, which correspond to the first and second dissociation energies, respectively. The results show that the first and second dissociation of the V _ n defect is larger than that of Vn-1 and V _ n _ 1 when n is even number, that is, the defects of V _ 2, V _ 4 and V _ 6 are more stable. (4) for zigzag single-walled carbon nanotubes, the minimum vacancy formation energy tube diameter in each type of V _ n shows an increasing trend as a whole, and when the n value in the zigzag _ 0) tube is a multiple of 3, the energy gap is the smallest. This minimum vacancy formation energy is smaller than expected.
【學(xué)位授予單位】：內(nèi)蒙古科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB383.1;O613.71

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