What's in a shape? Towards a unifying picture of bonding and crystal complexity

Sharon C. Glotzer, PhD

Professor and Chair

Chemical Engineering

University of Michigan

ABSTRACT: Chemical bonds are among the most fundamental concepts in science. They describe the way in which atoms associate to form molecules and compounds, and they have been a central paradigm of science for a century. Today, powerful software packages that solve quantum mechanical theories of chemical bonding are in routine use to predict molecular and crystal structures. Are analogous capabilities possible for predicting colloidal crystals, where nanoparticles play the role of atoms? In this talk, we discuss a remarkable finding that has emerged from twenty years of global nanoscience research: Aside from differences in length, time and energy scales, atoms and nanoparticles can self-assemble into identical crystal structures, including those with large, complex unit cells. These colloidal crystal structures are possible even in the absence of explicit nanoparticle interactions, further demonstrating that statistical thermodynamics is agnostic to the forces driving self-assembly. What sort of "bonding" describes these structures, which emerge as the particles become crowded and are stabilized solely by entropy maximization? We discuss these questions and present a new theory of entropic bonding that has important analogies with chemical bonding theory. With entropic bonding theory, we can predict colloidal crystal structures from nanoparticle shape in the same way that chemical bonding theory predicts atomic crystal structures from electronic valence.

BIOGRAPHY: Sharon C. Glotzer is the John W. Cahn Distinguished University Professor of Engineering and the Stuart W. Churchill Collegiate Professor of Chemical Engineering and Professor of Materials Science and Engineering at the University of Michigan, Ann Arbor, and also holds faculty appointments in Physics, Applied Physics, and Macromolecular Science and Engineering. Since July 2017 she is the Anthony C. Lembke Department Chair of Chemical Engineering at the University of Michigan. Her research on computational assembly science and engineering aims toward predictive materials design of colloidal and soft matter. Using computation, geometrical concepts, and statistical mechanics, her research group seeks to understand complex behavior emerging from simple rules and forces, and use that knowledge to design new materials. Glotzer's group also develops and disseminates powerful open-source software including the particle simulation toolkit, HOOMD-blue, which allows for fast molecular simulation of materials on graphics processors, the signac framework for data and workflow management, and freud for analysis and visualization. (https://github.com/glotzerlab/)

Glotzer received her Bachelor of Science degree in Physics from UCLA and her PhD in Physics from Boston University. She is a member of the National Academy of Sciences, the National Academy of Engineering, and the American Academy of Arts and Sciences. She is a Fellow of the Materials Research Society, the American Association for the Advancement of Science, the American Institute of Chemical Engineers, the American Physical Society, and the Royal Society of Chemistry. Glotzer is the recipient of numerous awards and honors, including the 2019 Aneesur Rahman Prize for Computational Physics from the American Physical Society, the 2018 Nanoscale Science and Engineering Forum and the 2016 Alpha Chi Sigma Awards both from the American Institute of Chemical Engineers, and the 2019 Fred Kavli Distinguished Lectureship in Materials Science, 2017 Materials Communications Lecture Award and 2014 MRS Medal from the Materials Research Society. Glotzer is a leading advocate for simulation-based materials research, including nanotechnology and high performance computing, serving on boards and advisory committees of the National Science Foundation, the U.S. Department of Energy, and the National Academies. She is currently a member of the National Academy of Sciences Division on Engineering and Physical Sciences Committee.