Hosted by Dr. Yong Yang
Department of Materials Science and Engineering Seminar Series
Tuesday, April 4, 2017 – 4:05-4:55p.m. – 270 FLG
Yang Zhang, Ph.D.
Department of Nuclear, Plasma, and Radiological Engineering
Department of Materials Science and Engineering
Program of Computational Science and Engineering
University of Illinois at Urbana-Champaign
Hiking on the Energy Landscape and Counting
Energy landscape, the high-dimensional hypersurface in the configuration space, has been a valuable concept in qualitatively describing non-equilibrium matter and the associated complex processes that occur over a very long timescale, such as the viscous flow of supercooled liquids, the folding of polypeptide chains into structured proteins, and the self-assembly of micro-units into functional objects. Despite extensive theoretical and computational studies, the enduring challenge is still how to quantify the energy landscape experimentally. To address this challenge, we developed a Relaxation-Excitation Mode Analysis (REMA) framework, which incorporates the kinetic theory and the energy landscape theory by treating the many-body collisions explicitly. Using REMA, important statistics of the activation barriers (“mountains”) and metabasins (“valleys”) of the energy landscape become accessible from experimentally measurable two-point correlation functions, e.g. using quasi-elastic and inelastic scattering experiments. We further verified this methodology by direct sampling of the potential energy landscape using a history-dependent metadynamics simulation. In this talk, first, I will show the intriguing energy landscape characteristics of three apparently-different systems: glass-forming metallic liquids, water, and proteins; then, I will describe our quantitative investigations of how confinement blocks the transition pathways on the energy landscape of proteins and thus prevents their thermal denaturation/unfolding. Our REMA method can be generalized to provide quantitative descriptions of the energy landscapes of a plethora of non-equilibrium matter, processes, and phenomena, and thus may directly influence applications involving understanding and preventing the aging and degradation of materials, protein preservation, and the design and manufacture of novel amorphous materials.
Prof. Yang Zhang received a B.S. in Electrical Science and Technology from University of Science and Technology of China in 2004, and a Ph.D. in Nuclear Science and Engineering from Massachusetts Institute of Technology in 2010. He then worked at Oak Ridge National Laboratory as the recipient of the Clifford G. Shull Fellowship from 2010 to 2012. In Fall 2012, he joined the faculty of Department of Nuclear, Plasma, and Radiological Engineering at University of Illinois at Urbana-Champaign, with affiliate appointments from Department of Materials Science and Engineering, Program of Computational Science and Engineering, and Beckman Institute of Advanced Science and Technology. He is interested in the fundamental science (especially the long timescale phenomena and rare events) as well as the applications of a range of non-equilibrium materials. These materials contain novel non-equilibrium structures intentionally designed to highlight specific functions and thus often carry unique properties. His current research can be roughly divided into two areas: 1) extreme properties of liquids; 2) glassy, jammed, and kinetically trapped soft matter. [http://zhang.npre.illinois.edu/]