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. In recent months, the coronavirus pandemic has stopped all 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, however, need to be nominated by their advisors.  Seminars will take place on Fridays, from 11 AM-12 PM. During 2021, we expect to hold two seminar per month, at the last two Fridays of each month.This event's talks:

​Flow Induced Crystallization in Polymers

​Prof. Gregory Rutledge (Massachusetts Institute of Technology)

​Abstract: The Crystallization is an essential step in the processing of most polymers.  It takes place under conditions of rapid cooling and high strain rate, and is strongly accelerated relative to quiescent conditions.  The initial step in this process is flow-enhanced nucleation (FEN), which occurs on time and length scales that are hard to capture experimentally.  To resolve this problem, we use nonequilibrium molecular dynamics simulations to characterize FEN from a melt of linear polyethylene-like chains. Both short and long (entangled) chains are simulated.  First, methods are described for identifying the critical nucleation event using mean first-passage times (MPFT).  Fitting of the data to a master equation is used to extract important thermodynamic and kinetic quantities.  Results for nucleation kinetics accelerated under different modes of deformation, e.g. simple shear or uniaxial extension, and rates of strain are used to assess the nature of FEN, and new models based on the orientational ordering of Kuhn segments induced by flow are proposed.  Evidence is presented for a breakdown of classical nucleation theory for entangled polymer melts at high strain rates, which in turn is traced to the flow-induced formation of nematic domains in the melt.  The appearance of such domains suggests a different perspective on the underlying physics of flow-enhanced nucleation of long chain molecules. 

​Speaker Bio: Gregory C. Rutledge is the Lammot du Pont Professor of Chemical Engineering at the Massachusetts Institute of Technology (MIT) and the Lead PI for MIT in AFFOA, a Manufacturing Innovation Institute focused on functional fabrics. He served as Director of the Program in Polymer Science and Technology and as Executive Officer in the Department of Chemical Engineering at MIT.  He is a Fellow of the American Institute of Chemical Engineers, the American Physical Society, and the Polymer Materials Science and Engineering (PMSE) Division of the American Chemical Society.  He is a recipient of The Founders Award of the Fiber Society, and was the H.A. Morton Distinguished Visiting Professor in Polymer Science at the University of Akron, and a Thinker in Residence at Deakin University in Geelong, Australia.  Prof. Rutledge’s research on molecular engineering of soft matter examines relationships between processing, structure and properties of engineered polymers, using statistical mechanics and knowledge of their molecular structure. His expertise includes both computations and experiments. His group has been instrumental in the development of molecular level modeling of polymer crystals, crystallization kinetics, and the structure and properties of semicrystalline materials. Since 2001 he and his coworkers have published extensively on the fabrication, properties and applications of ultrafine polymer fibers formed by electrospinning. Prof. Rutledge is an editor for the Journal of Materials Scienceand serves on several editorial boards.  

​First-principles control of zeolite phase competition and intergrowth

​Mr. Daniel Schwalbe-Koda (Massachusetts Institute of Technology)

​Abstract: Zeolites are versatile materials for heterogeneous catalysis due to their large topological and compositional diversity. Although this diversity allows tailoring a zeolite towards chemical reactions, phase competition between polymorphs often hinders the crystallization of a single framework. Computational methods can aid zeolite synthesis by proposing organic structure-directing agents (OSDAs) that template desired structures. However, most simulations are performed for one framework at a time, and cannot predict whether OSDAs are more likely to synthesize another polymorph instead of the desired one. Here, we propose a first-principles approach to control zeolite phase selectivity using high-throughput simulations. We start developing algorithms that accelerate zeolite-OSDA simulations by two orders of magnitude compared to existing methods. Then, we calculate more than half a million host-guest pairs, from which we compute binding affinity metrics that rationalize phase competition in zeolites. The metrics explain synthesis outcomes from more than one thousand articles extracted from the literature and enable the design of selective, chemically simple OSDAs. Experimental results show that the proposed templates additionally enhance the catalytic properties of the obtained frameworks, outperforming state-of-the-art catalysts. Finally, we predict and realize an intergrowth using a single bi-selective OSDA, thus imprinting reaction selectivities to the resulting structure by tuning phase competition. This work offers a platform for controlling zeolite synthesis and catalytic properties through polymorphism engineering.

​Speaker Bio: Daniel Schwalbe-Koda is a PhD candidate in the Department of Materials Science and Engineering at MIT, and a current MIT Energy Fellow. His research combines high-throughput calculations, density functional theory and statistical learning to accelerate the synthesis and design of zeolites and transition metal oxides for catalysis. He also develops machine learning methods for differentiable atomistic simulations, and applies human-computer interaction to materials design. Prior to MIT, Daniel received a B.Sc. degree in Electrical Engineering and an M.Sc. degree in Physics from the Aeronautics Institute of Technology, Brazil.