Acoustic phonons in nanostructures

纳米结构中的声学声子

• 批准号: 312440-2008
• 负责人: Murray, Daniel
• 金额: $ 1.27万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2008
• 资助国家: 加拿大
• 起止时间: 2008-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=396831
• 关键词: Acoustic; phonons; nanostructures

Vibrations of small metal spheres embedded in a glass block can be observed using reflected laser light. The wavelength of a steady laser beam is shifted up or down according to the frequency of the vibration in Raman scattering. The vibrations can be more directly observed using brief pulses of laser light shorter than one billionth of a second. Theoretical work is needed to calculate the frequencies of these vibrations, taking into consideration the elastic response of the metal as well as the shape and surroundings of the metal sphere. Molecular dynamics simulations, in which the positions and velocities of many (up to 100000) point masses are calculated with time on a computer, are used. The Fourier transform of the motion is used to find the frequencies of individual modes. Materials with direction dependent (anisotropic) speed of sound can be simulated in this way. Nanoclusters with non-spherical shape can also be handled. Finally, the effect of a surrounding material, such as a glass block, can be studied. The results of these investigations will give new insight into the mechanical properties of very small objects. This knowledge has potential future application when very small mechanical devices are designed.

使用反射激光可以观察嵌入玻璃块中的小金属球的振动。稳定激光束的波长根据拉曼散射振动的频率向上或向下移动。使用短于十亿分之一秒的短激光脉冲可以更直接地观察振动。需要进行理论工作来计算这些振动的频率，同时考虑金属的弹性响应以及金属球的形状和周围环境。使用分子动力学模拟，其中在计算机上随时间计算许多（最多 100000 个）点质量的位置和速度。 运动的傅里叶变换用于查找各个模式的频率。可以通过这种方式模拟具有方向相关（各向异性）声速的材料。也可以处理非球形的纳米团簇。最后，可以研究周围材料（例如玻璃块）的影响。 这些研究的结果将为非常小的物体的机械特性提供新的见解。 当设计非常小的机械设备时，这些知识在未来有潜在的应用。