TD-DFT and TD-DFTB Investigation of the Optical Properties and Electronic Structure of Silver Nanorods and Nanorod Dimers.
TD-DFT and TD-DFTB Investigation of the Optical Properties and Electronic Structure of Silver Nanorods and Nanorod Dimers.
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DOI：
10.1021/acs.jpcc.8b05196
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发表时间：
2018-10-18
期刊：
影响因子：
--
通讯作者：
Aikens CM
中科院分区：
文献类型：
--
作者：
Alkan F;Aikens CM
在这里，我们使用时间相关密度泛函理论（TD-DFT）和时间相关密度泛函紧密结合（TD-DFTB）对银纳米棒的电子结构和光学性质进行理论研究。与 TD-DFT 相比，TD-DFTB 通常在准确描述银纳米棒二聚体组装的尺寸和类型方面表现良好。然而，与 TD-DFT 水平计算的值相比，TD-DFTB 纳米棒纵向和横向峰的能量和强度在某种程度上被低估。通过利用 TD-DFTB 的计算效率，我们还将研究范围扩展到更长的纳米棒及其包含多达 2000 个原子的二聚体。我们的结果表明，纳米棒之间的耦合以及二聚体组件的光学特性很大程度上取决于单体的长度。在所有情况下，二聚体中的能量变化作为间隙距离的函数明显偏离偶极-偶极相互作用模型。此外，分数位移（Δλ/λ0）对纳米棒长度依赖性的最佳拟合曲线的比较表明，等离子标尺方程的参数取决于纳米棒的长度和组件的类型，而不是接近通用值。这些见解是通过 TD-DFTB 的计算效率及其处理大型纳米棒二聚体系统中的量子力学效应的能力实现的。
Here, we perform theoretical investigation using time-dependent density functional theory (TD-DFT) and time-dependent density functional tight binding (TD-DFTB) for the electronic structure and optical properties of silver nanorods. TD-DFTB generally performs well for the accurate description of optical properties with respect to the size and type of dimer assembly of silver nanorods compared to TD-DFT. However, the energies and intensities of the longitudinal and transverse peaks of the nanorods are somewhat underestimated with TD-DFTB compared to the values calculated at the TD-DFT level. By exploiting the computational efficiency of TD-DFTB, we also extend our investigation to longer nanorods and their dimers containing up to ∼2000 atoms. Our results show that the coupling between nanorods and the resulting optical properties of the dimer assemblies are quite dependent on the length of the monomers. In all cases, the energy shifts in dimers as a function of the gap distance deviate significantly from the dipole–dipole interaction model. Moreover, a comparison of the best-fit curves for the dependence of the fractional shifts (Δλ/λ0) on nanorod length indicates that the parameters of the plasmon ruler equation depend on the length of the nanorods and the type of the assembly rather than approaching a universal value. These insights are enabled by the computational efficiency of TD-DFTB and its ability to treat quantum mechanical effects in large nanorod dimer systems.
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