Zhang Qiubo, Song Zhigang, Wang Yu, Nie Yifan, Wan Jiawei, Bustillo Karen C, Ercius Peter, Wang Linwang, Sun Litao, Zheng Haimei
Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices, School of Molecular Science and Engineering, South China University of Technology, Guangzhou 510640, China.
Sci Adv. 2022 Oct 7;8(40):eabp9970. doi: 10.1126/sciadv.abp9970.
Twinning frequently occurs in nanocrystals during various thermal, chemical, or mechanical processes. However, the nucleation and propagation mechanisms of twinning in nanocrystals remain poorly understood. Through in situ atomic resolution transmission electron microscopy observation at millisecond temporal resolution, we show the twinning in Pb individual nanocrystals via a double-layer swap motion where two adjacent atomic layers shift relative to one another. The swap motion results in twin nucleation, and it also serves as a basic unit of movement for twin propagation. Our calculations reveal that the swap motion is a phonon eigenmode of the face-centered cubic crystal structure of Pb, and it is enhanced by the quantum size effect of nanocrystals.
孪晶在各种热、化学或机械过程中经常出现在纳米晶体中。然而，纳米晶体中孪晶的成核和传播机制仍知之甚少。通过以毫秒时间分辨率进行的原位原子分辨率透射电子显微镜观察，我们展示了铅单个纳米晶体中的孪晶是通过双层交换运动形成的，其中两个相邻原子层相对彼此发生位移。这种交换运动导致孪晶成核，并且它还作为孪晶传播的基本运动单元。我们的计算表明，这种交换运动是铅面心立方晶体结构的一种声子本征模式，并且它因纳米晶体的量子尺寸效应而增强。
