A Building Block Approach to Controlling Phonon Dynamics in Nanostructures

晶体材料的许多物理性质(即电子、光学、热)源于原子排列的周期性和波与潜在重复结构的相互作用的性质。随着纳米技术的出现，现在有机会引入更多的几何结构，包括增加一层周期性，以便在更广泛的空间和时间尺度上操纵属性。这项研究的目标是开发理论和计算工具，用于分析和阐明周期性纳米材料中的复杂弹性波现象，并设计具有优越性能和先进功能的集成材料-结构系统。为了实现这一目标，将采用积木方法，首先分析和设计单个单元。然后，这些电池将在结构层面上被利用，以实现目标机械和热性能和功能。为了促进这种多尺度的分析和设计过程，将开发和利用快速晶格动力学计算技术。所提出的理论工作将得到实验研究的验证，这将使材料/结构分析和设计在纳米尺度上成为可能。这将导致块状纳米结构系统以及降维纳米机电系统(NEMS)组件的热性能和振动响应特性的实质性改善。特别令人感兴趣的是可实现的材料系统，其热导率降低，以实现高效的热电转换，以及坚固的纳米结构，能够以最小的散热抑制振动。

Much of the physical properties (i.e., electronic, optical, thermal) of crystalline materials stems from the periodicity in the atomic arrangement and the nature of wave interactions with the underlying repetitive structure. With the advent of nanotechnology there are now opportunities to introduce additional geometric structures including an added layer of periodicity in order to manipulate properties over broader spatial and temporal scales. The objective of the proposed research is the development of theoretical and computational tools for the analysis and elucidation of complex elastic wave phenomena in periodic nanoscale materials and the design of integrated material-structure systems with superior properties and advanced functionalities. This objective will be approached by adopting a building blocks methodology where single unit cells are first analyzed and designed. The cells will then be utilized at the structural level to achieve target mechanical and thermal properties and functionalities. In order to facilitate this multiscale analysis and design process, techniques for fast lattice dynamics calculations will be developed and utilized.The proposed theoretical work, which will be validated by experimental studies, will enable new approaches for material/structure analysis and design at the nanoscale. This will lead to substantial improvements in thermal properties and vibration response characteristics in bulk nanostructured systems as well as reduced dimension nanoelectromechanical system (NEMS) components. Of particular interest are realizable material systems with reduced thermal conductivity for efficient thermoelectric conversion and robust nanoscale structures capable of suppressing vibration with minimum heat dissipation.