题目：Beyond Crystallography: Coherent Diffractive Imaging and Atomic Electron Tomography
报告人：Jianwei Miao University of California Los Angeles
地点： 教十二-201
时间： 5月26日，周五，15:00-16:00
摘要：
The discovery and analysis of X-ray diffraction from crystals by Max von Laue, William Henry Bragg and William Lawrence Bragg in 1912 marked the birth of crystallography. Over the last century, crystallography has been fundamental to the development of many fields of science. However, many samples in physics, chemistry, materials science, nanoscience, geology, and biology are non-crystalline, and thus their 3D structures are not accessible by traditional crystallography. Overcoming this hurdle has required the development of new structure determination methods. In this talk, I will present two methods that can go beyond crystallography: coherent diffractive imaging (CDI) and atomic electron tomography (AET). In CDI, the diffraction pattern of a non-crystalline sample or a nanocrystal is first measured and then directly phased to obtain an image. The well-known phase problem is solved by combining the oversampling method with iterative algorithms. In the first part of the talk, I will illustrate several important CDI methods and highlight some important applications using 3rd generation synchrotron radiation and X-ray free electron lasers. In the second part of the talk, I will present a general tomographic method, termed AET, for 3D structure determination of crystal defects and disordered materials at the single atomic level. By combining advanced electron microscopes with novel data analysis and powerful computational algorithms, AET has been used to reveal the 3D atomic structure of crystal defects and chemical order/disorder such as grain boundaries, anti-phase boundaries, stacking faults, dislocations and point defects, and to precisely localize the 3D coordinates of individual atoms in materials without assuming crystallinity. The experimentally measured coordinates can then be used as direct input for quantum mechanical calculations of material properties such as atomic spin and orbital magnetic moments and local magnetocrystalline anisotropy. As coherent X-ray sources and powerful electron microscopes are under rapid development around the world, we expect that CDI and AET will find broad applications in both the physical and biological sciences.
J. Miao, T. Ishikawa, I. K. Robinson and M. M. Murnane, “Beyond crystallography: Diffractive imaging using coherent x-ray light sources”, Science 348, 530-535 (2015). (Review)
J. Miao, P. Ercius and S. J. L. Billinge, "Atomic electron tomography: 3D structures without crystals", Science 353, aaf2157 (2016). (Review)
Y. Yang, C.-C. Chen, M. C. Scott, C. Ophus, R. Xu, A. Pryor Jr, L. Wu, F. Sun, W. Theis, J. Zhou, M. Eisenbach, P. R. C. Kent, R. F. Sabirianov, H. Zeng, P. Ercius and J. Miao, “Deciphering chemical order/disorder and material properties at the single-atom level”, Nature 542, 75-79 (2017).
个人简介：
Dr. Jianwei Miao is Professor of Physics & Astronomy and the California NanoSystems Institute at UCLA. He received a B.S. degree in physics from Hangzhou University (now Zhejiang University) in 1991, an M.S. in Physics from Chinese Academic Sciences in 1994, a Ph. D. in Physics and an M.S. in computer science from State University of New York at Stony Brook in 1999. After graduation, he became a Staff Scientist at SLAC National Accelerator Laboratory, Stanford University. In 2004, he moved to UCLA as an Assistant Professor and was promoted to Full Professor in 2009. Dr. Miao is a pioneer in the development of novel imaging methods with X-rays and electrons. He performed a seminal experiment on extending X-ray crystallography to allow structure determination of non-crystalline specimens in 1999. This method, known as coherent diffractive imaging (CDI) or computational microscopy, has been broadly implemented using synchrotron radiation, X-ray free electron lasers, high harmonic generation, optical lasers, and electrons. In 2012, Dr. Miao pioneered atomic electron tomography (AET) for 3D atomic structure determination of materials without assuming crystallinity. In 2013, he applied AET to image the 3D core structure of edge and screw dislocations in materials at atomic resolution. More recently, he determined the 3D coordinates of more than 23,000 atoms in an FePt nanoparticle with 22 pm precision and correlated chemical order/disorder and crystal defects with material properties at the single atomic level.
Dr. Miao is a Fellow of the American Physical Society, an Associate Editor for Science Advances, and an Associate Editor for Crystallography Reviews. His other honors include the Werner Meyer- Ilse Memorial Award (1999), an Alfred P. Sloan Research Fellowship (2006-2008), the Outstanding Teacher of the Year Award in the Department of Physics & Astronomy at UCLA (2006-2007), a Kavli Frontiers Fellowship (2010), a Theodore von Kármán Fellowship from the RWTH Aachen University in Germany (2013), the Microscopy Today Innovation Award (2013) and the University of Strasbourg Institute for Advanced Study (USIAS) Fellowship, France (2015-2017). He has been a Guest Scientist of the Institute of Physical and Chemical Research (RIKEN) in Japan since 2004, and a Guest Professor of Zhejiang University in China since 2009.
欢迎老师和同学参加！
