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arXiv 1301.4162cond-mat.mes-hallcond-mat.mtrl-sci
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Stone-Wales缺陷可以导致碳纳米管中的金属-半导体转变,这取决于它们的取向

Stone-Wales defects can cause a metal-semiconductor transition in carbon nanotubes depending on their orientation

P. Partovi-Azar, A. Namiranian

摘要:

研究表明,碳纳米管表面的Stone-Wales(SW)缺陷具有两种不同的取向,即纵向和周向SW缺陷,导致了两种不同的电子结构。基于密度泛函理论,我们已经表明,纵向SW缺陷不打开附近的费米能的带隙,而一个相对较小的带隙出现在管与周向缺陷。我们认为,在周向SW缺陷的存在下的带隙开放是长程对称性破缺的结果,可以沿着管的所有方式传播。具体而言,由于缺陷的存在而导致的收缩和拉伸键长的分布以及低能电子(即2 pz电子)的跳跃能显示了两种类型缺陷的两种不同模式。对于不同的缺陷浓度的几何特征和电子性质的管之间的相互作用也进行了研究。考虑到$π$ -轨道电荷密度,它也已被证明,键长从其松弛长度的偏差导致在不同的掺杂的缺陷周围的两个缺陷取向-电子丰富的圆周缺陷和空穴丰富的纵向缺陷。我们还表明,在管具有两种类型的缺陷,周向缺陷将占主导地位,并施加其电子特性。

英文摘要:

It has been shown that the two different orientations of Stone-Wales (SW) defects, i.e. longitudinal and circumferential SW defects, on carbon nanotubes (CNTs) result in two different electronic structures. Based on density functional theory we have shown that the longitudinal SW defects do not open a bandgap near the Fermi energy, while a relatively small bandgap emerges in tubes with circumferential defects. We argue that the bandgap opening in the presence of circumferential SW defects is a consequence of long-range symmetry breaking which can spread all the way along the tube. Specifically, the distribution of contracted and stretched bond lengths due to the presence of defects, and hopping energies for low-energy electrons, i.e. the 2pz electrons, show two different patterns for the two types of defects. Interplay between the geometric features and the electronic properties of the tubes have also been studied for different defect concentrations. Considering $π$-orbital charge density, it has also been shown that the deviations of bond lengths from their relaxed length result in different doping for two defect orientations around the defects -- electron-rich for a circumferential defect and hole-rich for a longitudinal one. We have also shown that, in the tubes having both types of defects, circumferential defects would dominate and impose their electronic properties.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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