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首页> 外文会议>International Conference of Computational Methods in Sciences and Engineering 2007(ICCMSE 2007); 20070925-30; Corfu(GR) >Density Functional Studies of the ~(13)C NMR Chemical Shifts in Single-Walled Carbon Nanotubes
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Density Functional Studies of the ~(13)C NMR Chemical Shifts in Single-Walled Carbon Nanotubes

机译：单壁碳纳米管中〜（13）C NMR化学位移的密度泛函研究

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摘要

Density functional theory has been used to compute the electronic structure and ~(13)C NMR chemical shifts of finite (9,0) single-walled carbon nanotubes (SWNTs) capped with fullerene hemispheres and with hydrogen atoms. The chemical shifts and HOMO-LUMO gaps were found to be dependent upon the mode of capping. The shifts of semiconducting and metallic tubes were estimated as being around 130 ppm and 141 ppm, respectively. Periodic boundary calculations on infinite zigzag (n,0) SWNTs with 7 ≤ n ≤ 17 were performed. These entities can be characterized by a family index, λ =mod(n,3), and the chemical shifts can be fitted well by a function inversely proportional to the diameter of the tube and proportional to a constant which depends on the nanotube family. Direct comparison of the molecular and periodic approaches can be made if benzene is used as the internal reference. Such a comparison indicates that capping may have a strong effect on the computed properties. Calculations on infinite zigzag (7 ≤ n ≤ 10) amine functionalized SWNTs have been performed. The functional group may react with a C-C bond which is parallel or diagonal to the tube axis and both sites have been considered. The shifts of the carbons directly attached to the group are sensitive to the bond which has been functionalized and may therefore be used to discriminate between the two products. Functionalization induces a significant line broadening of the NMR signals but it does not dramatically change the average shift of the unfunctionalized SWNT carbons.
机译：密度泛函理论已用于计算被富勒烯半球和氢原子覆盖的有限（9,0）单壁碳纳米管（SWNT）的电子结构和〜（13）C NMR化学位移。发现化学位移和HOMO-LUMO间隙取决于加帽模式。估计半导体管和金属管的位移分别约为130 ppm和141 ppm。对7≤n≤17的无限之字形（n，0）SWNT进行周期性边界计算。这些实体可以用族指数λ= mod（n，3）来表征，并且化学位移可以通过与管的直径成反比并与取决于纳米管族的常数成正比的函数很好地拟合。如果使用苯作为内部参照物，则可以直接比较分子和周期性方法。这样的比较表明封顶可能对计算出的属性有很大的影响。已经进行了无限之字形（7≤n≤10）胺官能化单壁碳纳米管的计算。所述官能团可以与与管轴平行或对角的C-C键反应，并且已经考虑了两个位点。直接连接到该基团上的碳原子的转移对已被官能化的键敏感，因此可用于区分两种产物。官能化引起NMR信号显着的谱线加宽，但不会显着改变未官能化的SWNT碳的平均位移。

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