Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session S26: Predicting Rare Event Kinetics in Complex Systems with Theory, Simulations and Machine Learning IIIFocus Live
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Sponsoring Units: DCP Chair: Sapna Sarupria, Clemson University; Matteo Salvalaglio, University College London |
Thursday, March 18, 2021 11:30AM - 12:06PM Live |
S26.00001: Marshaling the Resources of First Principles Theory and High Performance Computing to Predict the Chemistry of Combustion Invited Speaker: Stephen Klippenstein A quantitative description of the conversion of a fuel into products and pollutants requires a chemical model with ~103 species and ~104 reactions. Notably, many low flux/rare event reactions are of central importance to this chemistry. For example, ignition behavior is largely determined by the sequential addition of two O2 molecules to a radical. Similarly, soot formation involves growth pathways that are secondary to the oxidative conversions, while NOx formation generally involves high barriers. The key intermediates in these reaction sequences generally have peak mole fractions of 10-4 or less. |
Thursday, March 18, 2021 12:06PM - 12:18PM Live |
S26.00002: Auto-construction of complex reaction networks in heterogeneous catalysis Weiqi Wang, Xiangyue Liu, Jesús Pérez-Ríos In this work, we propose an approach for the auto-construction of complex reaction networks in heterogeneous catalysis. In particular, we employ ab initio replica exchange molecular dynamics (MD) to sample the chemical space, followed by a Markov state model built from the MD trajectories to construct the reaction networks without prior knowledge about the energy landscape. Finally, the transition path theory (TPT) method is then employed to calculate the transition rates of different transition pathways in the reaction network. As a result, the contributions of different stable and meta-stable configurations of the catalysts to the reaction can be quantified at finite temperatures. This approach is illustrated in a model reaction, the O2 activation on Ag4 clusters. |
Thursday, March 18, 2021 12:18PM - 12:30PM Live |
S26.00003: An off-lattice kinetic Monte Carlo kernel guided by topological and geometrical analysis to bridge accurate ab-initio calculations and large scale simulations Miha Gunde, Nicolas Salles, Nicolas Richard, Anne Hemeryck, Layla Martin Samos The kMC method is traditionally used on-lattice, where a property |
Thursday, March 18, 2021 12:30PM - 12:42PM Live |
S26.00004: Kinetics of adamantane disassociation via reactive molecular simulations and infrequent metadynamics Nehzat Safaei, Omar Valsson Adamantane and other diamondoid molecules have been proposed as precursor seeds for the controlled growth of nanodiamonds [1-3]. An important question for such applications is understanding how adamantane's disassociation depends on the temperature and pressure conditions. In this study, we investigate the kinetics of adamantane disassociation via reactive ReaxFF [4] molecular dynamics simulations and infrequent metadynamics [5]. We focus on the interplay between carbon-carbon and carbon-hydrogen bond breaking and how it depends on pressure and temperature. |
Thursday, March 18, 2021 12:42PM - 12:54PM Live |
S26.00005: Stochastic A Priori Dynamics for Complex Reactive Chemical Environments Daniel R Moberg, Christopher Knight, Ahren Jasper The first-principles modeling of energetic chemical environments with use-inspired complexities is an ongoing challenge. We describe a stochastic framework for predicting the chemistry of complex systems that is scalable and well-suited for leveraging high performance computing resources. Elementary chemical events are treated using detailed semiclassical theories that include treatments for nonadiabatic transitions, tunneling, and zero-point energy maintenance combined with high-accuracy potential energy surfaces constructed automatically via ab initio permutationally invariant polynomials. Competition between elementary events is modeled stochastically to enable simulations of complex networks of reactions and to access long timescales. Applications of the stochastic model include quantifying the effects of rare nonthermal events in many body gas phase systems relevant to combustion, where highly reactive but transient energized species are formed, as well as low temperature atmospheric chemistry characterizing the reactivity of transient complexes. |
Thursday, March 18, 2021 12:54PM - 1:06PM Live |
S26.00006: Exploration of complex reaction systems with the Chemical Trajectory analYzer (CTY) and CVHD acceleration Can Huang, Yuqing Zhao, Peiyang Yu, Nils Baur, Wassja Kopp, Kai Leonhard In this study, we investigate the acceleration of reactive molecular dynamics (rMD) simulations to explore complex chemical reaction networks. We demonstrate how identification of species and reactions is facilitated by the Chemical Trajectory analYzer (CTY) tool that simultaneously detects reaction pathways and computes rate constants. All geometries of reactants, transition states and products are saved for higher-level calculations. This automated PES mapping allows for coupling to mechanism and master equation software and studying overall ignition and combustion behavior of fuels. |
Thursday, March 18, 2021 1:06PM - 1:18PM Live |
S26.00007: Kinetic Simulations Of Charge Injection Kinetics From Ultrafast Experiments To Steady State Conditions Thomas Cheshire, Jeb Boodry, M. Kyle Brennaman, Paul Giokas, David Zigler, Andrew Moran, John Papanikolas, Gerald Meyer, Thomas Meyer, Frances Houle We are building towards a multiscale description of solar energy conversion in dye-sensitized solar cells (DSSC). We reported in an initial study a kinetic framework for the femtosecond to microsecond photophysics of a set of ruthenium complexes in solution that produces simulated time-resolved spectroscopic signals that are in quantitative agreement with experiments. Additionally, we have demonstrated that datasets of dynamical observations and steady state measurements are both necessary to predict dye interactions under 1-sun conditions. We discuss extensions of our kinetic framework to 1) compare the excitation and decay kinetics of ruthenium complexes in solution and on ZrO2 films where there is no charge transfer, 2) establish competing intramolecular transitions and charge transfer to TiO2, and 3) illustrate that by including explicit experimental interactions in our model, rate coefficients for charge injection, not phenomenological lifetimes, are estimated. Results for simulations under solar irradiance are discussed in context of DSSCs. |
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