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Center for Soft and Living Matter Seminar: “Medium-range Order and Local Structure Fluctuations in Metallic Glass”
November 11 at 12:30 PM - 1:30 PM
Amorphous materials have no long-range order, but there are ordered structures at short-range (2-5 Å), medium-range (5-20 Å), and even longer-length scales. While regular and semiregular polyhedra are often identified as short-range order in amorphous materials, the nature of the medium-range order has remained elusive. Because of the disorder, the dynamics also become far more complicated. For example, the vibrational spectrum of glasses shows an excess density of states. This is known as the Boson Peak and has been found to be a ubiquitous feature of amorphous materials. In this talk, I will present recent studies of metallic glass using neutron and synchrotron X-ray scattering. The development of medium-range order in driving liquid-to-liquid phase transitions will be highlighted. For the dynamics, the momentum dependence of the inelastic scattering intensity reveals spatial correlation at different time scales. The role of local structure fluctuations will be discussed.
Xun-Li Wang
Professor of Physics, City University of Hong Kong
Professor Wang received his Ph.D. from Iowa State University and B.S. from Peking University, both in Physics. He is an elected Fellow of the American Physical Society (APS), American Association for the Advancement of Science (AAAS), Neutron Scattering Society of America (NSSA). In 2024, he was elected to the Board of Directors of the American Physical Society.
In August 2012, Professor Xun-Li Wang joined City University of Hong Kong as a Chair Professor and Head of the Department of Physics and Materials Science. In July 2017, the department split and Professor Wang assumed the headship of the new Department of Physics starting with 12 faculty members. Prior to coming to Hong Kong, he had been working at Oak Ridge National Laboratory in the US, rising through the ranks to Distinguished Staff Member. He was responsible for the design, construction, and commissioning of VULCAN, a powerful engineering diffractometer at the Spallation Neutron Source, Oak Ridge National Laboratory. As a senior scientist in the Neutron Science Directorate, he led innovative research, using neutron scattering as a primary tool, to understand deformation and phase transformation behavior in complex materials.