A Building Block Approach to Controlling Phonon Dynamics in Nanostructures

许多物理性质（即，晶体材料的电子、光学、热）特性源于原子排列的周期性和波与底层重复结构相互作用的性质。随着纳米技术的出现，现在有机会引入额外的几何结构，包括增加的周期性层，以便在更广泛的空间和时间尺度上操纵属性。 拟议的研究的目标是理论和计算工具的开发，用于分析和阐明周期性纳米材料中的复杂弹性波现象，并设计具有上级性能和先进功能的集成材料结构系统。这一目标将通过采用积木方法来实现，其中首先分析和设计单个单元电池。然后，将在结构水平上利用这些单元，以实现目标机械和热性能和功能。为了促进这种多尺度分析和设计过程，将开发和利用快速晶格动力学计算技术，提出的理论工作，这将通过实验研究进行验证，将使新的方法，在纳米尺度上的材料/结构分析和设计。这将导致大规模纳米结构系统以及尺寸减小的纳米机电系统（NEMS）组件的热性能和振动响应特性的显著改善。特别令人感兴趣的是可实现的材料系统，其具有用于有效热电转换的降低的热导率和能够以最小的热耗散抑制振动的稳健的纳米级结构。

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.