Statistical Thermodynamics & Molecular Simulations (STMS) Seminar Series

​These seminar series are aimed at providing a virtual platform for sharing scientific research in the area of statistical mechanics, molecular simulations, and computational materials science. Since early 2020, the coronavirus pandemic has disrupted many large in-person scientific gatherings, including conferences and department seminars, and it is not clear that the situation will improve any time soon. STMS is aimed at filling this gap, and provide a venue for dissemination of research findings and exchange of ideas in the age of COVID.  This model is being currently used by several other scientific communities, and can potentially continue even beyond the pandemic if successful. 

​Each seminar will be a 60-minute event and will comprise of a long-form (30-minute) talk by a principal investigator or a senior research scientists from academia or industry and a short-form (15-minute) presentation by a graduate student or a postdoc. The remainder of the event will be dedicated to Q&A (10 minutes for the PI, 5 minutes for the student/postdoc). Long-form speakers will be chosen by the STMS Organizing Committee, while we encourage suggestions from the community at large. Student and postdoctoral speakers can either be nominated by their advisors or can self-nominate themselves by sending a CV to the organizers.  During 2022 we expect to hold two seminar per month, and the events will take place in the last two Fridays of each month, from 10:45 AM-12:00 PM Eastern Standard Time (EST):

​This event's talks:

​Fluctuating interfaces and the bulk melting of ice

​Prof. Christoph Dellago (University of Vienna)

​Abstract: In systems with periodic boundary conditions, first order phase transitions involve the formation of slab-shaped clusters that can be long-lived particularly close to coexistence. In this case, transition pathways can be conveniently generated by shooting off dynamical trajectories from slab configurations, which are transition states that eventually relax into one of the two stable phases. Here, we first address the question of the width at which slabs typically rupture, initiating the transformation to more stable cluster shapes. Insight is obtained by modelling the motion of the fluctuating slab surfaces with a reaction-diffusion equation and solving it using a path integral formulation that exploits the correspondence of the reaction-diffusion equation with the Schrödinger equation. Our analysis shows that the width at which a slab ruptures scales logarithmically with system size, resulting in remarkably long-lived slabs down to small widths. Using this approach to generate unbiased transition trajectories near coexistence, we then study the molecular mechanism for the bulk melting of hexagonal ice, paying particular attention to the initial stages of the nucleation process. We find a wide array of possible reaction channels, most of whom involve so-called 5+7 defects. Only in later stages L-D defects as well as vacancy-interstitial pairs form, which then prompt the transition to the liquid state.

​Speaker Bio: Christoph Dellago is a professor of Computational Physics at Faculty of Physics of the University of Vienna. After obtaining his PhD in physics in 1996, he worked as postdoctoral researcher at the University of California at Berkeley, funded by a Schrödinger Fellowship of the Austrian Science Foundation. In 1999 he started his independent career as Assistant Professor at the University of Rochester before returning to the University of Vienna in 2003 as full professor.

​In his research, Prof. Dellago focuses on the development of simulation algorithms and their application to investigate dynamical processes in condensed matter systems. In particular, he has helped to create the transition path sampling methodology for the simulation of rare but important events, such as nucleation at first order phase transitions, chemical reactions and biomolecular reorganizations. More recently Prof. Dellago has worked on applying machine learning methods to molecular structure recognition and the representation of potential and free energy surfaces. Recent research topics include self-assembly of nanocrystals, folding and unfolding of biopolymers, interfaces in aqueous systems, phase separation in alloys, thermo-polarisation, cavitation, freezing and non-equilibrium work fluctuations.

​Professor Dellago has served in various administrative positions, for instance as Vice-Dean and then Dean of the Faculty of Physics of the University of Vienna, and has organized numerous scientific meetings including the 11th Liquid Matter Conference, the 41th Meeting of the Middle European Collaboration in Statistical Physics (MECO) as well as numerous topical workshops. He has served as President of the Council of CECAM and currently he is the director of the Erwin Schrödinger Institute of Mathematics and Physics at the University of Vienna.

​Hierarchical self-assembly pathways of peptoid helices and sheets

​Dr. Mingfei Zhao(University of Chicago)

​Abstract: Peptoids (N-substituted glycines) are a class of tailorable synthetic peptidomic polymers. Amphiphilic diblock peptoids have been engineered to assemble 2D crystalline lattices with applications in catalysis and molecular separations. Assembly is induced in an organic solvent/water mixture by evaporating the organic phase, but the assembly pathways remain uncharacterized. We conduct all-atom molecular dynamics simulations of Nbrpe6Nc6 as a prototypical amphiphilic diblock peptoid. We identify a thermodynamically controlled assembly mechanism by which monomers assemble into disordered aggregates that self-order into 1D chiral helical rods then 2D achiral crystalline sheets. We support our computational predictions with experimental observations of 1D rods using small angle x-ray scattering and circular dichroism, and 2D crystalline sheets using x-ray diffraction and atomic force microscopy. This work establishes new understanding of hierarchical peptoid assembly and principles for the design of peptoid-based nanomaterials.

​ Speaker Bio: Mingfei Zhao obtained her Ph.D. in Mechanical Engineering from the State University of New York at Binghamton. She got her bachelor’s and master’s degrees from Shandong University in China. She is currently a postdoctoral scholar at the University of Chicago with Prof. Andrew L. Ferguson. Her current research uses computational modeling to examine hierarchical colloidal/biomolecular self-assembly across scales, with a particular focus on all-atom/coarse-grained simulations of hierarchical peptoid self-assembly.