Bulletin of the American Physical Society
73rd Annual Gaseous Electronics Virtual Conference
Volume 65, Number 10
Monday–Friday, October 5–9, 2020; Time Zone: Central Daylight Time, USA.
Session TR1: Modeling and Simulation: Chemical ReactionsLive
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Chair: Annemie Bogaerts, University of Antwerp |
Thursday, October 8, 2020 10:00AM - 10:15AM Live |
TR1.00001: Global Model Framework to Identify Relevant Species and Reactions in Chemically Complicated Plasma Systems Janez Krek, Yangyang Fu, De-Qi Wen, John Verboncoeur Plasma chemistry mechanisms in plasma assisted combustion (PAC) systems involve a large number of species in reaction chains. Simulations with spatially dependent system variables, e.g. densities and temperatures, become prohibitively computationally expensive. We present a kinetic global model framework (KGMf), coupled with a Boltzmann equation solver for dynamic evaluation of the electron energy distribution function (EEDF) and the sensitivity analysis, to identify the most important species and reactions. Our model employs spatially-averaged energy and particle balance equations, chemical reactions in bulk plasma, taking into account time-dependent power absorption via Joule heating, energy and particle loss to the wall through an analytic collisional sheath model, to determine the role of each species and reaction on steady-state densities and temperatures. It is important to note that a species may be a critical component of a reaction chain leading to an important product, despite low density due to high creation and conversion rates. This enables determination of key species and reactions that are required in spatially dependent simulations. [Preview Abstract] |
Thursday, October 8, 2020 10:15AM - 10:30AM Live |
TR1.00002: Data-Driven Global Model for Low-Temperature Plasma Dynamics Christine Greve, Manoranjan Majji, Kentaro Hara Plasma reactions have been studied experimentally and computationally to better understand the behavior of plasma. Zero-dimensional, global models can include an array of ground, excited, and ionized states of various gas species. This work uses a physically-informed extended Kalman filter coupled with a global model to estimate plasma properties and reaction rate coefficients. The filter uses a predictor-corrector scheme to update the computational estimate as measurement data are acquired in time to better inform the physics-based model as the system evolves. This method is applied to plasma oscillations in a Hall effect thruster to estimate plasma properties using the discharge current oscillation data from measurements. The applications to other low-temperature plasma phenomena will be discussed. [Preview Abstract] |
Thursday, October 8, 2020 10:30AM - 10:45AM Live |
TR1.00003: DFTB+ simulation of B$_{\mathrm{x}}$N$_{\mathrm{y}}$ species formation for boron nitride nanotubes synthesis Omesh Dhar Dwivedi, Yuri Barsukov, Igor Kaganovich, Sierra Jubin, Stephane Ethier Using DFTB+ MD simulations we analyze B$_{\mathrm{x}}$N$_{\mathrm{y}}$ species formation in a cooling mixture of boron atoms and nitrogen dimer. These species could be precursors of boron nitride nanotubes (BNNTs) synthesis. We determine that DFTB+ cannot predict correctly reaction of boron atoms and boron dimers with nitrogen molecules. The first reaction produces BN$_{\mathrm{2}}$ molecule and simulations show it to be stable, even at T > 3000K. This is incorrect since BN$_{\mathrm{2}}$ molecule dissociates into B and N$_{\mathrm{2}}$ from the ${}^{2}$B$_{\mathrm{2}}$ state which has higher energy than BN$_{\mathrm{2}}$(${}^{2}$A$_{\mathrm{1}}$). DFTB+ is not able to reproduce transition from ${}^{2}$A$_{\mathrm{1}}$ to ${}^{2}$B$_{\mathrm{2}}$ state. Similarly, stable BNBN molecule is difficult to observe in these simulations, since the reaction leading to formation of BNBN has a high energy barrier and is kinetically hindered. Nevertheless, DFTB+ simulations show formation of planar B$_{\mathrm{2}}$N$_{\mathrm{2}}$ and BBN$_{\mathrm{2}}$ molecules and larger clusters (B$_{\mathrm{3}}$N$_{\mathrm{3}}$ , B$_{\mathrm{12}}$N$_{\mathrm{12}}$, etc). Finally, we analyze the thermodynamic feasibility of these reactions through minimization of Gibbs Energy of formation. [Preview Abstract] |
Thursday, October 8, 2020 10:45AM - 11:00AM Live |
TR1.00004: Kinetic Modeling of Metal Oxide Chemistry and Particle Formation in a Plasma Flow Reactor Mikhail Finko, Davide Curreli, Batikan Koroglu, Timothy Rose, David Weisz, Jonathan Crowhurst, Harry Radousky Current understanding of metallic chemistry in extreme environments, such as nuclear fireballs, remains limited due to the challenging conditions present and the multitude of physical processes and timescales involved. In this work, we focus on the intermediate millisecond timescale of the problem by studying the evolution of metallic species in the rapidly cooling conditions of a plasma flow reactor. Using a global kinetic approach, we model the formation of molecular oxides as well as the nucleation, condensation, and coagulation processes that lead to nanoparticle formation and growth. In particular, the coupling between chemical kinetics and particle formation processes is implemented via the Simultaneous Particle and Molecule Modeling (SPAMM) approach of Pope and Howard. The resulting evolution of species concentrations and particle size distributions for iron, aluminum, and uranium is analyzed and compared with in situ and ex situ measurements. This work aims to bridge the gap between short timescale plasma chemistry and long timescale debris formation - a critical deficiency in current extreme environment models. [Preview Abstract] |
Thursday, October 8, 2020 11:00AM - 11:15AM Live |
TR1.00005: The utility of dynamic adaptive chemistry for simulations of plasma-surface interaction Jose Alfredo Millan-Higuera, Venkattraman Ayyaswamy The interaction of low-temperature plasmas with various surfaces exposed to it is an actively studied problem with relevance to several applications including plasma medicine, plasma-assisted surface modification, and plasma etching to name a few. From a computational perspective, the role of plasma chemistry cannot be stressed enough in order to be able to capture important mechanisms observed in experiments. In general, studies which emphasize on the plasma chemistry tend to include a large number of species and reactions for these simulations. While some researchers have performed sensitivity analysis studies and proposed reduced chemistry mechanisms, it is still not clear if the reduction based on certain conditions will work at other conditions. In order to address this disadvantage, we borrow computational techniques that are popular in the combustion community to develop a computational framework that allows for dynamic chemistry reduction in plasma chemistry simulations. This talk will present preliminary results obtained using the in-house computational framework for a 0-D simulation as well as a 1-D simulation of a plasma facing a dielectric. The decrease in computational cost and accuracy as a result of the dynamic reduction are both quantified for argon, helium and air plasmas. [Preview Abstract] |
Thursday, October 8, 2020 11:15AM - 11:30AM |
TR1.00006: Quantum chemistry modeling of B$_{\mathrm{n}}$N$_{\mathrm{2}}$ clusters formation in reaction between small B$_{\mathrm{n}}$ clusters (n$=$2-4) and N$_{\mathrm{2}}$ molecule for boron nitride nanotubes synthesis. Yuri Barsukov, Igor Kaganovich, Omesh Dwivedi, Sierra Jubin, Stephane Ethier We study precursors for the boron nitride nanotubes (BNNTs) formation that can effectively convert molecular nitrogen into boron nitride. The data have been obtained by using a DFT (density function theory) method with unrestricted WB97X-D functional with 6-311$+$G(2dp) basis set. Using quantum chemistry methods, we discovered that formation of linear BNBN, cyclo-BNBNB and cyclo-BNBNB$_{\mathrm{2}}$ species from B$_{\mathrm{n}}$ (n$=$2-4) and N$_{\mathrm{2}}$ proceeds through sequential steps, and activation barrier of the rate-limited step is near 1.1 eV for all considered B$_{\mathrm{n}}$ clusters. On the other hand, the highest barrier towards dissociation of BNBN, cyclo-BNBNB and cyclo-BNBNB$_{\mathrm{2}}$ species on B$_{\mathrm{n}}$ and N$_{\mathrm{2}}$ increases and equals 2.5, 4.8 and 5.6 eV respectively. Thus, based on our calculations we can conclude that N$_{\mathrm{2}}$ is able to react with small B$_{\mathrm{n}}$ clusters producing new B$_{\mathrm{n}}$N$_{\mathrm{2}}$ clusters with BN bonds, and these B$_{\mathrm{n}}$N$_{\mathrm{2}}$ clusters can be accumulated in the gas phase even at high temperature providing contribution in the BNNTs growth. [Preview Abstract] |
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