Structure-property relation is a foundation of materials science and engineering. Atomic structure is at the center of this endeavor that guides and helps material design, processing, application, and basic scientific understanding of material properties. We are truly fortunate to be able to “see” atomic structures in crystalline materials where Bragg diffraction is made possible by the periodic atomic packing. In amorphous solids, the structural disorder is down to the atomic scale that has prevented us from observing atomic structure. As a result, the important structure-property relation has remained a mystery up to date.
In this talk, I will review two widely accepted hypotheses of atomic packing in metallic glasses, one is the atomic cluster packing and the other the fractal packing. These two proposed atomic structures cover the short- and medium-range ordering with universality across many materials systems. Here I will show that neither the cluster nor the fractal packing is convincingly rooted in physics. For example, the icosahedral cluster is found not to be the local atomic packing with the lowest energy as previously thought, and the fractal packing does not exist at all.
These contradicting finding, however, does not solve the issues of the atomic structure, instead pose more questions to us. In this talk, I will explain the reasons and arguments behind our findings and pose new questions that may inspire students and researchers to join the work for discovery of the atomic structure of amorphous solids and liquids.
Professor Mo Li received his B.S, in materials science from Central South University in China and Ph.D. in applied physics from Caltech. After a brief staying as a postdoctoral fellow at Caltech and the Argonne National Laboratory, he joined the investment bank Morgan Stanley & Co. in New York. He came back to academia in 1998. From 1998 to 2001, he was an assistant professor at the Johns Hopkins University. Currently, he is a professor at the Georgia Institute of Technology. He is the recipient of the National Thousands Talent Program Award of China and the Alexander von Humboldt Young researcher award.
Professor Li's research focuses on understanding fundamental properties and processes of materials, and predicting material behaviors. The approaches used in his research are a blend of those from statistical physics, solid state physics, materials science, metallurgy, mechanics and large scale, high performance computing. His research focuses on algorithm development, simulation, and theoretical analysis.