Colloidal nanocrystal superlattices as phononic crystals: plane wave expansion modeling of phonon band structure
Colloidal nanocrystal superlattices as phononic crystals: plane wave expansion modeling of phonon band structure
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作为声子晶体的胶体纳米晶体超晶格：声子能带结构的平面波展开建模
DOI：
10.1039/c6ra03876j
复制
发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
Wang, Robert Y.
中科院分区：
文献类型：
--
作者：
Sadat, Seid M.;Wang, Robert Y.
胶体纳米晶体由无机晶体核心和与表面结合的有机配体组成，并自然地自组装成称为超晶格的周期性阵列。这种周期性结构使得超晶格在声子晶体应用中具有前景。为了探索这种潜力，我们使用平面波展开方法来模拟声子带结构。我们发现，这些超晶格的纳米级周期性产生声子带隙，具有非常高的中心频率在102 GHz的顺序。我们还发现，大的声学对比度之间的硬的双金属核和软的配体矩阵导致非常大的声子带隙宽度的顺序为101 GHz。我们有系统地改变的α-core直径，d，α-core弹性模量，ENC核心，粒子间的距离（即配体长度），L，和配体弹性模量，Eligand，并报告相应的影响上的声子带结构。我们的模型表明，带隙中心频率随着d和L的减小而增大，或者随着ENC核和Eligand的增大而增大。带隙宽度与d、L、ENC芯和Eligand呈非单调关系，这些变量的相互耦合可以消除带隙。最后，我们在许多超晶格中观察到多个声子带隙，并发现带隙数量的增加与d和ENC核心的增加之间存在相关性。我们发现，声子晶体组件（即d/L和ENC核心/Eligand）之间的属性失配的增加会导致声子分支，并且是增加声子带隙数量的关键驱动因素。我们预测的声子带隙中心频率和宽度远远超过目前的实验演示的三维声子晶体。这表明，胶体超晶格是有前途的候选人，用于高频声子晶体的应用。
Colloidal nanocrystals consist of an inorganic crystalline core with organic ligands bound to the surface and naturally self-assemble into periodic arrays known as superlattices. This periodic structure makes superlattices promising for phononic crystal applications. To explore this potential, we use plane wave expansion methods to model the phonon band structure. We find that the nanoscale periodicity of these superlattices yield phononic band gaps with very high center frequencies on the order of 102 GHz. We also find that the large acoustic contrast between the hard nanocrystal cores and the soft ligand matrix lead to very large phononic band gap widths on the order of 101 GHz. We systematically vary nanocrystal core diameter, d, nanocrystal core elastic modulus, ENC core, interparticle distance (i.e. ligand length), L, and ligand elastic modulus, Eligand, and report on the corresponding effects on the phonon band structure. Our modeling shows that the band gap center frequency increases as d and L are decreased, or as ENC core and Eligand are increased. The band gap width behaves non-monotonically with d, L, ENC core, and Eligand, and intercoupling of these variables can eliminate the band gap. Lastly, we observe multiple phononic band gaps in many superlattices and find a correlation between an increase in the number of band gaps and increases in d and ENC core. We find that increases in the property mismatch between phononic crystal components (i.e. d/L and ENC core/Eligand) flattens the phonon branches and are a key driver in increasing the number of phononic band gaps. Our predicted phononic band gap center frequencies and widths far exceed those in current experimental demonstrations of 3-dimensional phononic crystals. This suggests that colloidal nanocrystal superlattices are promising candidates for use in high frequency phononic crystal applications.
DOI：
--
发表时间：
2016
期刊：
影响因子：
--
作者：
M. Nomura;R. Yanagisawa;J. Maire;R. Anufriev;and S. Volz
通讯作者：
and S. Volz
反物质表演光学体操
DOI：
--
发表时间：
2005
期刊：
影响因子：
--
作者：
J. Eades
通讯作者：
J. Eades