Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session A17: Matter in Extreme Environments: Energetic MaterialsFocus
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Sponsoring Units: DCOMP Chair: Maosheng Miao, California State University, Northridge Room: BCEC 156A |
Monday, March 4, 2019 8:00AM - 8:36AM |
A17.00001: Scalable Atomistic Simulations of Energetic Materials Invited Speaker: Aiichiro Nakano We have developed an extension of the divide-and-conquer algorithmic framework called divide-conquer-recombine to make quantum molecular dynamics (QMD) and reactive molecular dynamics (RMD) simulations scalable on emerging exascale supercomputers and beyond. On today’s supercomputing platform, for instance, the framework has achieved over 98% of the perfect speedup on 786,432 IBM Blue Gene/Q processors for 40 trillion electronic degrees-of-freedom QMD in the framework of density functional theory and 68 billion-atom RMD. Production simulations on energetic materials include: (1) dynamic phase transition, crossover in anisotropic mechanochemistry and multistage reaction pathways in energetic crystals; and (2) reaction dynamics and enhanced energetic performance of metallic-nanoparticle/graphene composites. |
Monday, March 4, 2019 8:36AM - 8:48AM |
A17.00002: Detonation on a tabletop in nitromethane: effects of sensitizers and desensitizers Mithun Bhowmick, Erin J Nissen, Dana Dlott We have developed a method to study shock to detonation process on a tabletop with high temporal and spatial resolution1. Here we present effects of additives on nitromethane (NM) detonation studied with optical pyrometry, photon doppler velocimetry, and high-speed video photography. Addition of ethylenediamine (EDA, 1% by wt.) reduces the detonation threshold from 20 GPa to 14 GPa of input pressures, while addition of acetone (up to 30% by wt.) inhibits the reaction and detonation is not at all observed for up to 20 GPa input pressure. With the help of optical pyrometry and high-speed videos, thermal properties of emission from the above mixtures were probed. Detonation experiments often measure the detonation shock wave using an optical window contacted to the explosive. We measured NM detonation in 9 different window materials and found that polycrystalline materials such as LiF are somewhat better than glasses, and both are much better than polymers, reported in earlier works. |
Monday, March 4, 2019 8:48AM - 9:00AM |
A17.00003: Sub-nanosecond carbon condensation under ultrafast shock compression of cryogenic liquid carbon monoxide Michael Armstrong, Rebecca Lindsey, Nir Goldman, I-Feng W. Kuo, Tian Li, Elissaios Stavrou, Joseph Michael Zaug, Sorin Bastea The detonation of negative oxygen-balance explosives typically results in the formation of carbon condensates, including nano-onions and nano-diamonds. Although the production of carbon nano-condensates can occur via detonation, the carbon chemistry required to form such products does not require detonation chemistry per se: a negative oxygen-balance organic reactant and high pressure and temperature conditions are likely sufficient to condense nanocarbon. Furthermore, although carbon chemistry during detonation is thought to require 10-100s nanosecond time scales, simulations suggest that condensation of carbon can occur on nanosecond or sub-nanosecond time scales. To explore these fundamental issues, here we present the results of experiments and simulations of ultrafast shock compression of a simple negative oxygen-balance reactant, cryogenic liquid carbon monoxide. |
Monday, March 4, 2019 9:00AM - 9:12AM |
A17.00004: Chemical behavior of strontium and magnesium oxalates at high-pressure Iskander G Batyrev, Jennifer A Ciezak-Jenkins, Michael Gojko Pravica
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Monday, March 4, 2019 9:12AM - 9:24AM |
A17.00005: Temperature evolution in plastic bonded explosives during impacts Nisha Mohan, Darby J Luscher, Marc Cawkwell, Kyle J Ramos
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Monday, March 4, 2019 9:24AM - 9:36AM |
A17.00006: Anisotropic Thermal Expansion of CL-20 Polymorphs from Ab initio Molecular Dynamics Simulations Igor Schweigert Hexanitrohexaazaisowurtizane (CL-20) is a high-density nitramine compound with several known polymorphs. Anisotropic thermal expansion coefficients for different polymorphs are needed to model effects of polymorphic impurities during thermal cycling. In this presentation, I will describe density functional theory (DFT) based molecular dynamics simulations of temperature-dependent lattice constants of the epsilon and gamma polymorphs and compare the results to available experimental data as well as predictions from density functional tight binding and ReaxFF-based molecular dynamics simulations. |
Monday, March 4, 2019 9:36AM - 9:48AM |
A17.00007: High pressure structural study of TATB: Evidence of a structural phase transition. Elissaios Stavrou, Brad A Steele, Samantha Clarke, Joseph Michael Zaug, Matthew Kroonblawd, I-Feng W. Kuo, Sorin Bastea, Laurence Fried, Jesse Smith, Vitali Prakapenka, Eran Greenberg, Oliver Tschauner High pressure unreacted isothermal equations of state (EOS) for energetic materials are needed for accurate modeling of detonation and shock initiation. EOS determination through conventional powder X-ray diffraction (XRD) experiments is often problematic due to the low-Z of constituent elements (typically CHNO) and the low symmetry of the corresponding crystal structure. To overcome this barrier for TATB, we performed a concomitant powder and single crystal (SC) XRD study. Our SC XRD results reveal a structural phase transition, reported for the first time, towards a monoclinic C-centered structure above 4-5GPa. Experimental results are supported by calculations using the USPEX evolutionary crystal structure prediction algorithm. The phase transition involves a pressure-induced alteration of the stacking of the layers of the TATB molecules. This results to a higher crystal symmetry, from triclinic to monoclinic, without an abrupt change of the volume per formula unit. |
Monday, March 4, 2019 9:48AM - 10:00AM |
A17.00008: WITHDRAWN ABSTRACT
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Monday, March 4, 2019 10:00AM - 10:12AM |
A17.00009: Computational design of new fused heterocyclic energetic materials Maija M Kukla, Roman Tsyshevskiy, Aleksandr S. Smirnov Linear oxadiazole-based energetic materials exhibit attractive performance and sensitivity characteristics compared to known conventional high energy density materials and are considered as appealing potential candidates to be used as explosives, propellants, and cast-melt ingredients in composite explosives. Despite all advantages of the oxadiazole-based compounds the improvements of their physical and chemical properties are bound by certain limits. It is impossible to create new material with significantly improved parameters by variation of oxadiazole rings within the linear molecule. A further step in enhancing explosive characteristics, i.e. higher performance and lower sensitivity, in heterocycles would be to probe a fused energetic molecules in which a stable (rigid) molecular core is functionalized with appropriate rings (or even combinations of rings). Here we report a systematic study that helps to reveal and optimize structure-property-function relationships in fused heterocyclic energetic materials. We show that arrangement of heterocyclic rings in fused molecules opens new opportunities for design new insensitive energetic materials with high performance. |
Monday, March 4, 2019 10:12AM - 10:24AM |
A17.00010: Probing Equations of State and Novel Phases of Energetic Crystals via First Principles Simulations Brad A Steele, I-Feng W. Kuo Energetic crystals are widely used in military and industrial applications. Modeling the shock propagation and initiation of energetic materials rely on the unreacted equation of state which can vary greatly if there is a phase transition. Many current models do not include phase transitions which can be difficult to detect in experiment. Furthermore, most first-principles based models use density functional theory that gives a poor description of dispersion. In this work, pressure-induced phase transitions and equations of state of energetic crystals are investigated using first-principles based approaches ranging from density functional theory to post-Hartree-Fock perturbative methods that give a better description of dispersion. Novel high-pressure phases are probed using crystal structure prediction method USPEX. The feasibility of using perturbative and hybrid methods to predict phase transition pressures is investigated. |
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