Curvature effects on the structural, electronic and optical properties of isolated single-walled carbon nanotubes within a symmetry-adapted non-orthogonal tight-binding model
Curvature effects on the structural, electronic and optical properties of isolated single-walled carbon nanotubes within a symmetry-adapted non-orthogonal tight-binding model
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DOI：
10.1088/1367-2630/6/1/017
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发表时间：
2004-02
影响因子：
3.3
通讯作者：
V. Popov
中科院分区：
文献类型：
--
作者：
V. Popov
使用碳的 2s 和 2p 电子，在对称适应的非正交紧束缚模型中研究了曲率对孤立单壁碳纳米管的结构、电子和光学性质的影响。对称适应方案允许将电子的矩阵特征值问题减少为任何纳米管类型的 8×8 矩阵的对角化。由于这种简化，可以计算晶胞中具有大量原子的纳米管的电子能带结构。利用该模型对187个中小半径纳米管的结构进行了优化。研究发现，当管半径小于5 Å时，优化结构与非优化结构的偏差较大。计算了101个中小半径纳米管的能带结构和介电函数。这些纳米管的光学跃迁能量源自介电函数，并绘制出与管半径的关系图。结果表明，结构优化对非正交紧束缚模型中获得的跃迁能引入了微小的变化。该模型中优化结构的跃迁能量与一些纳米管类型的可用从头计算数据非常吻合。另一方面，前者的结果与 π 带紧束缚模型中纳米管表征所使用的结果存在很大偏差，特别是对于小半径管。导出的跃迁能量可用于分配纳米管吸收光谱以及选择拉曼散射共振的纳米管类型。
The effects of curvature on the structure, electronic and optical properties of isolated single-walled carbon nanotubes are studied within a symmetry-adapted non-orthogonal tight-binding model using 2s and 2p electrons of carbon. The symmetry-adapted scheme allows reducing the matrix eigenvalue problem for the electrons to diagonalization of 8×8 matrices for any nanotube type. Due to this simplification, the electronic band structure of nanotubes with a very large number of atoms in the unit cell can be calculated. Using this model, the structure of 187 small- and moderate-radius nanotubes is optimized. It is found that the deviations of the optimized structure from the non-optimized one are large for tube radii smaller than 5 Å. The band structure and the dielectric function of 101 small- and moderate-radius nanotubes are calculated. The optical transition energies for these nanotubes are derived from the dielectric function and plotted versus tube radius. It is shown that the structural optimization introduces small changes to the transition energies obtained within the non-orthogonal tight-binding model. The transition energies for the optimized structure within this model agree well with the available ab initio data for a few nanotube types. On the other hand, the results for the former deviate widely from those used for nanotube characterization in π-band tight-binding model especially for small-radius tubes. The derived transition energies can be used for the assignment of nanotube absorption spectra and for the selection of nanotube types for which the Raman scattering is resonant.