Wang Kang, Molteni Carla, Haynes Peter D
Imperial College London, Department of Materials, Exhibition Road, London SW7 2AZ, U.K.
King's College London, Department of Physics, Strand, London WC2R 2LS, U.K.
Nano Lett. 2022 Jul 27;22(14):5922-5928. doi: 10.1021/acs.nanolett.2c01939. Epub 2022 Jul 7.
We study the effect of size on the vibrational modes and frequencies of nanoparticles, by applying a newly developed, robust, and efficient first-principles-based method that we present in outline. We focus on rutile TiO, a technologically important material whose bulk exhibits a softening of a transverse acoustic mode close to , which becomes unstable with the application of negative pressure. We demonstrate that, under these conditions, nanoparticles above a critical size exhibit unstable localized modes and we calculate their characteristic localization length and decomposition with respect to bulk phonons. We propose that such localized soft modes could initiate coherent structural phase transformations in small nanoparticles above a critical size.
我们通过应用一种新开发的、稳健且高效的基于第一性原理的方法（我们将简要介绍该方法）来研究尺寸对纳米颗粒振动模式和频率的影响。我们聚焦于金红石型TiO₂，这是一种在技术上很重要的材料，其体相在接近某一温度时会出现横向声学模式软化，并且在施加负压时会变得不稳定。我们证明，在这些条件下，超过临界尺寸的纳米颗粒会表现出不稳定的局域模式，并且我们计算了它们相对于体相声子的特征局域长度和分解情况。我们提出，这种局域软模式可能会在超过临界尺寸的小纳米颗粒中引发相干结构相变。
