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:
Field-theoretic simulations of cold bosons
Prof. Glenn Fredrickson (University of California, Santa Barbara)
Abstract: I will discuss a new approximation-free, finite-temperature method for simulating the equilibrium properties of many-boson systems. The technique involves a direct numerical attack on quantum field theories formulated in an imaginary time path integral representation using coherent states. We address the “sign problem” inherent to such theories by importance sampling in the complex plane of (d+1)-dimensional fields using a complex Langevin (CL) scheme.
We have recently shown that CL algorithms adapted from simulation methods for classical polymer field theories are equally effective on Bose quantum field theories [1]. As a first demonstration, we numerically reproduced the equation of state of an ideal Bose gas and mapped the normal fluid to superfluid critical transition (lambda line) of a Bose fluid with pairwise contact interactions by CL sampling coupled with finite-size scaling. The simulation method enjoys near-linear scaling with system size and the computational effort is remarkably independent of the number of bosons. Future work will include studies of ultracold gases subject to artificial gauge fields, models of quantum magnetism, and real-time quantum dynamics of Bose assemblies, all practically inaccessible with existing simulation methods.
[1] K. T. Delaney, H. Orland, and G. H. Fredrickson, Phys. Rev. Lett. 124, 070601 (2020). DOI 10.1103/PhysRevLett.124.070601
Speaker Bio: Glenn Fredrickson obtained his Ph.D. at Stanford University in 1984 and subsequently joined AT&T Bell Laboratories, where he was named Distinguished Member of the Technical Staff in 1989. In 1990 he moved to the University of California at Santa Barbara (UCSB), joining the faculties of the Chemical Engineering and Materials Departments. He served as Chair of Chemical Engineering from 1998 to 2001 and in 2001 founded the Mitsubishi Chemical Center for Advanced Materials (MC-CAM). Professor Fredrickson is currently a Distinguished Professor, holds the Mitsubishi Chemical Endowed Chair in Functional Materials, and serves as MC-CAM Director, and Director of UCSB’s Complex Fluids Design Consortium. He has over 380 refereed publications, one book, and more than 15 patents in fundamental and applied topics related to the statistical mechanics of soft materials, including polymers, colloids, and glasses. His current research involves the development of statistical field theory based computer simulation techniques for the design of nanostructured soft materials.
Honors include the Polymer Physics Prize of the American Physical Society, the Cooperative Research Award in Polymer Science and Engineering of the American Chemical Society, the Alpha Chi Sigma and Walker Awards of the American Institute of Chemical Engineers, the Materials Theory Award of the Materials Research Society, the Collaboration Success Award of the Council for Chemical Research, and election to the American Academy of Arts & Sciences, the American Association for the Advancement of Science, and the National Academy of Engineering USA.
Professor Fredrickson has advised a broad range of companies in areas related to chemical and soft material science and technology. He has chaired Technical Advisory Boards for Dow Chemical, Mitsubishi Chemical, Apeel Sciences, and Allergan Medical, and served on the Scientific Advisory Boards of Royal DSM, CSP Technologies, SiO2 Materials Science, and the renewable resource firms Segetis, Novomer, and Spero Renewables.
Since 2001, Professor Fredrickson has held various advisory and management positions with Mitsubishi Chemical Holdings Corporation (MCHC) and its subsidiaries. During the period 2001-2014, he was appointed as Corporate Science and Technology Advisor for Mitsubishi Chemical, Mitsubishi Rayon, and Mitsubishi Plastics. From 2009-2014, Professor Fredrickson served as Executive Director and Member of the Board of The KAITEKI Institute, a long-term strategy unit of MCHC. During the period 2014-2017 he was appointed as Chief Technology Officer and Managing Corporate Executive Officer of the R&D Strategy Office of Mitsubishi Chemical Holdings. Since June 2014, he has been a member of MCHC’s Board of Directors.
Anharmonic free energy of crystalline systems using harmonically assisted methods
Dr. Sabry Moustafa (State University of New York at Buffalo)
ABstract: Any comprehensive capability to compute material properties must encompass prediction of the crystal structure. Such capabilities, in turn, rely on knowledge of the total (harmonic and anharmonic) thermodynamic free energy. However, calculation of the anharmonic free energy is computationally expensive using standard methods; e.g., thermodynamic integration (TI) and λ integration (λI) methods. The origin of this inefficiency is due to not utilizing the harmonic character in the ensemble averages on a configuration-basis, rather, the anharmonic contribution is measured on an average-basis by subtracting the average harmonic contribution. Accordingly, these methods are not harmonically assisted.
We have developed a harmonically assisted method in which the harmonic character of the crystal is leveraged to greatly increase the efficiency. The method combines advantages from standard thermodynamic integration and our recently developed harmonically mapped averaging methods; hence the name TI-HMA. This approach reduced the CPU computational time by order(s) of magnitude compared to the standard approaches, which is important achievement especially when using expensive ab initio models (e.g., DFT). In this talk, I will present a comparative result of the TI-HMA method against standard approaches, in terms of both precision and accuracy, as published recently (Moustafa et al., J. Chem. Theory Comput. 2017, 13, 825−834).
Speaker Bio: Sabry Moustafa is currently a Postdoctoral Scientist working with Prof. David Kofke at the University at Buffalo, Department of Chemical and Biological Engineering, where he also received his Ph.D. in 2015. During his Ph.D. and Postdoctoral work, he has been developing a new formulation for molecular ensemble averages to greatly enhance the efficiency in measuring anharmonic properties of crystalline systems (e.g., free energy, pressure and heat capacity). His work has been implemented with ab initio (VASP) and classical (LAMMPS) packages.