Title: Observing crystal nucleation in four dimensions using atomic electron tomography

Abstract

Nucleation plays a critical role in many physical and biological phenomena that range from crystallization, melting and evaporation to the formation of clouds and the initiation of neurodegenerative diseases. However, nucleation is a challenging process to study in experiments, especially in the early stage when several atoms or molecules start to form a new phase from a parent phase. A number of experimental and computational methods have been used to investigate nucleation processes, but experimental determination of the three-dimensional atomic structure and the dynamics of early stage nuclei has been unachievable. Here we use atomic electron tomography to study early stage nucleation in four dimensions (4D: that is, including time) at atomic resolution. Using FePt nanoparticles as a model system, we find that early stage nuclei are irregularly shaped, each has a core of one to a few atoms with the maximum order parameter, and the order parameter gradient points from the core to the boundary of the nucleus. We capture the structure and dynamics of the same nuclei undergoing growth, fluctuation, dissolution, merging and/or division, which are regulated by the order parameter distribution and its gradient. These experimental observations are corroborated by molecular dynamics simulations of heterogeneous and homogeneousmore » nucleation in liquid–solid phase transitions of Pt. Our experimental and molecular dynamics results differ from classical nucleation theory, indicating that a theory beyond this is needed to describe early stage nucleation at the atomic scale. Looking forward, we anticipate that the reported approach will open the door to the study of many fundamental problems in materials science, nanoscience, condensed matter physics and chemistry, such as phase transition, atomic diffusion, grain boundary dynamics, interface motion, defect dynamics and surface reconstruction with 4D atomic resolution.« less

Authors:

Zhou, Jihan ^[1]; Yang, Yongsoo ^[2]; Yang, Yao ^[3]; Kim, Dennis S. ^[1]; Yuan, Andrew ^[1]; Tian, Xuezeng ^[1]; Ophus, Colin ^[3]; Sun, Fan ^[4]; Schmid, Andreas K. ^[3]; Nathanson, Michael ^[5]; Heinz, Hendrik ^[5]; An, Qi ^[6]; Zeng, Hao ^[4]; Ercius, Peter ^[3]; Miao, Jianwei ^[1]

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+ Show Author Affiliations

1. Univ. of California, Los Angeles, CA (United States). California NanoSystems Inst.
2. Univ. of California, Los Angeles, CA (United States). California NanoSystems Inst.; Korea Advanced Inst. of Science and Technology, Daejeon (South Korea)
3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
4. State Univ. of New York (SUNY), Buffalo, NY (United States); Univ. at Buffalo, NY (United States)
5. Univ. of Colorado, Boulder, CO (United States)
6. Univ. of Nevada, Reno, NV (United States)

Publication Date:

2019-06-26

Research Org.:

Univ. of California, Los Angeles, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Foundry

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division

OSTI Identifier:

1600536

Grant/Contract Number:  

[AC02-05CH11231]

Resource Type:

Accepted Manuscript

Journal Name:

Nature (London)

Additional Journal Information:

[Journal Name: Nature (London); Journal Volume: 570; Journal Issue: 7762; Related Information: See atomic structures deposited in the Materials Databank (https://www.materialsdatabank.org/)Other raw data and code:http://www.physics.ucla.edu/research/imaging/nucleation/index.html]; Journal ID: ISSN 0028-0836

Publisher:

Nature Publishing Group

Country of Publication:

United States

Language:

English

Subject:

77 NANOSCIENCE AND NANOTECHNOLOGY