Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session H20: Materials in Extremes: Novel Energetic MaterialsFocus
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Sponsoring Units: GSCCM DCOMP DMP Chair: Elissaios Stavrou, Lawrence Livermore National Laboratory Room: 319 |
Tuesday, March 15, 2016 2:30PM - 3:06PM |
H20.00001: The Promise and Challenge of Extended Solids of Nitrogen Invited Speaker: Jennifer Ciezak-Jenkins The extended solids of nitrogen are of considerable interest as high-energy-density materials, as it has been projected a transformation from a single-bonded polymeric-like material back to the more stable triply-bonded diatomic phase would release over 2.3 eV/atom, which is significantly higher than conventional energetic materials. Although a transformation to the single bonded cubic gauche structure was experimentally confirmed in 2005, efforts to recover this material to ambient conditions have been challenging and unsuccessful to date. In an effort to increase the metastability of the extended solid, recent studies have focused on mixing, or doping, the nitrogen with small amounts of secondary gases, such as hydrogen or carbon monoxide. It was been postulated the secondary gas would passivate the terminal ends thus increasing the stability of the nitrogen extended solid. Our group was the first to demonstrate such an approach could be used successfully to decrease the transition pressure for the formation of the nitrogen extended solid through doping with hydrogen. Although recent studies on nitrogen/hydrogen mixtures by other research groups have also observed several non-molecular nitrogen/hydrogen structures, recovery of these materials to ambient conditions has not yet been demonstrated. In this talk, I will describe our progress in the study of the synthesis, characterization, and recovery of extended solids of nitrogen from high pressure conditions from nitrogen/carbon monoxide mixtures. I will also detail results from our closely coupled modeling and simulation efforts and discuss how these results help guide our experimental efforts. New opportunities and challenges that have arisen in the course of our studies that will be pursued in the future will also be presented. [Preview Abstract] |
Tuesday, March 15, 2016 3:06PM - 3:18PM |
H20.00002: Sodium Pentazolate: a Nitrogen Rich Energetic Material Ivan Oleynik, Brad Steele Sodium pentazolates NaN$_{\mathrm{5}}$ and Na$_{\mathrm{2}}$N$_{\mathrm{5}}$, new energetic materials, are discovered using first principles crystal structure search for the compounds of varying amounts of elemental sodium and nitrogen. The pentazole anion (N$_{\mathrm{5}}^{\mathrm{-}})$ is stabilized in the condensed phase by sodium Na$^{\mathrm{+}}$ cations at pressures exceeding 20 GPa, and becomes metastable upon release of pressure, i.e. at ambient conditions. The sodium azide (NaN$_{\mathrm{3}})$ precursor for the new compounds is predicted to undergo a chemical transformation above 50 GPa into sodium pentazolates NaN$_{\mathrm{5}}$ and Na$_{\mathrm{2}}$N$_{\mathrm{5}}$. The calculated Raman spectrum of NaN$_{\mathrm{5}}$ is in agreement with the experimental Raman spectrum of a previously unidentified substance appearing upon compression and heating of NaN$_{\mathrm{3}}$ precursor, thus confirming the appearance of the new compound. [Preview Abstract] |
Tuesday, March 15, 2016 3:18PM - 3:30PM |
H20.00003: Modeling of formation of extended NH solids under high pressure. Iskander G. Batyrev Structure of N-H extended network under high pressure was modelled using the evolutionary algorithm program USPEX based on plane wave DFT calculations (VASP). Concentration ratio of N$_{\mathrm{2}}$ to H$_{\mathrm{2}}$ gases was 3:1, 4:1, and 9:1. Range of the studied pressures was 10 -- 50 GPa on compression, and from 50 to 1 GPa on isotropic decompression of the extended network. Formation of an extended network with covalent bonds occurs between 30-50 GPa. Higher concentration of N requires higher pressure to form a covalent bond network. New structure of NH extended solids with covalent bonds are predicted: with P-1(CI-1) symmetry group for 9:1 ratio, with PBAM (D2H$+$9) symmetry group for 4:1 ratio, and with P-1(CI-1) for 3:1 ratio of N$_{\mathrm{2}}$ to H$_{\mathrm{2}}$ gas. Calculations of the mixtures of N$_{\mathrm{2\thinspace }}$and H$_{\mathrm{2}}$ gases at pressures in the range of 10-20 GPa resulted in a variety of structures without a covalent network, but consisting of nitrogen-containing molecules. For example, the lowest energy structure for a 3:1 ratio of N to H atoms consists of tetrazene and N$_{\mathrm{2\thinspace }}$molecules. At 10 GPa the lowest energy structure appears to be a combination of protonated ammonia and N$_{\mathrm{2}}$ molecules. [Preview Abstract] |
Tuesday, March 15, 2016 3:30PM - 3:42PM |
H20.00004: Computational design of fused heterocyclic energetic materials Roman Tsyshevskiy, Philip Pagoria, Iskander Batyrev, Maija Kuklja A continuous traditional search for effective energetic materials is often based on a trial and error approach. Understanding of fundamental correlations between the structure and sensitivity of the materials remains the main challenge for design of novel energetics due to the complexity of the behavior of energetic materials. State of the art methods of computational chemistry and solid state physics open new compelling opportunities in simulating and predicting a response of the energetic material to various external stimuli. Hence, theoretical and computational studies can be effectively used not only for an interpretation of sensitivity mechanisms of widely used explosives, but also for identifying criteria for material design prior to its synthesis and experimental characterization. We report here, how knowledge on thermal stability of recently synthesized materials of LLM series is used for design of novel fused heterocyclic energetic materials, including DNBTT (2,7-dinitro-4H,9H-bis([1,2,4]triazolo)[1,5-b:1',5'-e][1,2,4,5]tetrazine), compound with high thermal stability, which is on par or better than that of TATB. [Preview Abstract] |
Tuesday, March 15, 2016 3:42PM - 3:54PM |
H20.00005: \textbf{Metalloid Clusters as Novel Energetic Materials: Progress and Challenges}. Sufian Alnemrat, Joseph Hooper Integration of combustible metals is a standard route for increasing the energy density of explosive and propellant formulations. Bulk metals, however, have well-known limitations. As a rather different route, we have been studying molecular scale metalloid clusters that contain a core of low-valence metal surrounded by a layer of organic ligands. These materials may retain the high energy density of bulk metals but offer substantially faster reaction kinetics. In this talk we present recent computational results on the stability and decomposition of these clusters. We compare molecular dynamics simulations of the oxidation of a prototype aluminum metalloid cluster to recent experimental thermally programmed reaction data; both show that oxygen reacts with the metal core and not the ligands. As a route to larger-scale fabrication of these clusters, we present simulations of the nucleation and growth of small metalloid systems on functionalized graphene layers. The simulations demonstrate that spontaneous cluster nucleation and growth is favorable on many graphene defects, suggesting a means of templated growth of clusters and nanoparticles. [Preview Abstract] |
Tuesday, March 15, 2016 3:54PM - 4:06PM |
H20.00006: Novel LLM series high density energy materials: Synthesis, characterization, and thermal stability Philip Pagoria, Maoxi Zhang, Roman Tsyshevskiy, Maija Kuklja Novel high density energy materials must satisfy specific requirements, such as an increased performance, reliably high stability to external stimuli, cost-efficiency and ease of synthesis, be environmentally benign, and be safe for handling and transportation. During the last decade, the attention of researchers has drifted from widely used nitroester-, nitramine-, and nitroaromatic-based explosives to nitrogen-rich heterocyclic compounds. Good thermal stability, the low melting point, high density, and moderate sensitivity make heterocycle materials attractive candidates for use as oxidizers in rocket propellants and fuels, secondary explosives, and possibly as melt-castable ingredients of high explosive formulations. In this report, the synthesis, characterization, and results of quantum-chemical DFT study of thermal stability of LLM-191, LLM-192 and LLM-200 high density energy materials are presented. [Preview Abstract] |
Tuesday, March 15, 2016 4:06PM - 4:18PM |
H20.00007: ABSTRACT WITHDRAWN |
Tuesday, March 15, 2016 4:18PM - 4:30PM |
H20.00008: Mixed Nitrogen-Methane Solids at High Density Serge Desgreniers Mixing different molecular species may yield weakly bound compounds or van der Waals solids upon the application of high pressure. Van der Waals solids differ in physical properties from solids formed by pure molecular species at comparable thermodynamic conditions. In this contribution, we present results of the formation of binary methane-nitrogen compounds at high density. Methane and nitrogen, with similar potentials and molecular size, are expected to be partly miscible in the condensed state. Using single crystal and powder X-ray diffraction with synchrotron radiation and vibrational spectroscopy, the pressure-concentration phase diagram for this system has been explored from 1 to 16 GPa, at room temperature. The existence of van der Waals solid phases for samples with concentrations above 10{\%} (methane per volume) is demonstrated. For example, at 7.6 GPa and at room temperature, whereas pure nitrogen and methane exist in cubic and in rhombohedral structures, respectively, our study indicates that a methane-nitrogen sample with 60{\%} nitrogen by volume exhibits, under the same conditions, a novel phase with a tetragonal symmetry. Other novel structures in methane-nitrogen samples with different concentrations under varying pressure conditions have also been observed and will be discussed. [Preview Abstract] |
Tuesday, March 15, 2016 4:30PM - 4:42PM |
H20.00009: High Pressure Structures and Equations of State of HIO3 and HIO3O8 Joseph Zaug, Elissaios Stavrou, Brian Little, Sorin Bastea, Jonathan Crowhurst Knowledge of high-pressure thermodynamic properties of iodine containing oxides and acids is important toward improving the accuracy of semi-empirical predictions of extreme condition explosive and combustive chemistry of iodine containing formulations. Here we report on the synthesis of explosive chemical products HIO3 and HIO3O8 and on the structures and isotropic equations of state up to 35 and 45 GPa respectively. EOS model parameters are provided including parametrized exponential-6 interatomic potential values used to conduct thermochemical calculations of iodine containing reactants. [Preview Abstract] |
Tuesday, March 15, 2016 4:42PM - 4:54PM |
H20.00010: Harvesting materials formed under extreme conditions: Synthesis and isolation of nanocarbons derived from detonation of high explosives Millicent Firestone, Bryan Ringstrand, Rachel Huber, Dana Dattelbaum, Richard Gustavson, David Podlesak High explosive detonation products are primarily composed of molecular gases and solid carbon products. Recent studies have shown that the solid carbon condensate morphologies can vary depending on the high explosive and / or the pressure, temperature, or environment of the detonation. These studies have revealed, for example, unique carbon nanoparticles possessing novel morphologies, such as ones composed of hollow cores surrounded by lamellar structured graphitic shells. Despite these observations little work has been done to isolate these particles from the recovered post-detonation soot. This lack of effort to isolate and purify these products limits our understanding of their materials properties and, ultimately our ability to adapt them for useful materials. Herein, we report our recent studies directed at the production of nano-carbons through the detonation of a high explosive (e.g., composition B) under a range of experimental conditions. We further describe work directed at isolation and purification of the carbon nanoparticles. [Preview Abstract] |
Tuesday, March 15, 2016 4:54PM - 5:06PM |
H20.00011: Simulation of Initiation in Hexanitrostilbene Aidan Thompson, Tzu-Ray Shan, Cole Yarrington, Ryan Wixom We report on the effect of isolated voids and pairs of nearby voids on hot spot formation, growth and chemical reaction initiation in hexanitrostilbene (HNS) crystals subjected to shock loading. Large-scale, reactive molecular dynamics simulations are performed using the reactive force field (ReaxFF) as implemented in the LAMMPS software. The ReaxFF force field description for HNS has been validated previously by comparing the isothermal equation of state to available diamond anvil cell (DAC) measurements and density function theory (DFT) calculations. Micron-scale molecular dynamics simulations of a supported shockwave propagating in HNS crystal along the [010] orientation are performed ($u_p$ = 1.25 km/s, $U_s$ =4.0 km/s, $P$ = 11GPa.) We compare the effect on hot spot formation and growth rate of isolated cylindrical voids up to 0.1 µm in size with that of two 50nm voids set 100nm apart. Results from the micron-scale atomistic simulations are compared with hydrodynamics simulations. [Preview Abstract] |
Tuesday, March 15, 2016 5:06PM - 5:18PM |
H20.00012: Large-Amplitude Deformation and Bond Breakage in Shock-Induced Reactions of Explosive Molecules Jeffrey Kay The response of explosive molecules to large-amplitude mechanical deformation plays an important role in shock-induced reactions and the initiation of detonation in explosive materials. In this presentation, the response of a series of explosive molecules (nitromethane, 2,4,6-trinitrotoluene [TNT], and 2,4,6-triamino-1,3,5-trinitrobenzene [TATB]) to a variety of large-amplitude deformations are examined using ab initio quantum chemical calculations. Large-amplitude motions that result in bond breakage are described, and the insights these results provide into both previous experimental observations and previous theoretical predictions of shock-induced reactions are discussed. [Preview Abstract] |
Tuesday, March 15, 2016 5:18PM - 5:30PM |
H20.00013: Reactive Force Field for Liquid Hydrazoic Acid with Applications to Detonation Chemistry David Furman, Faina Dubnikova, Adri van Duin, Yehuda Zeiri, Ronnie Kosloff The development of a reactive force field (ReaxFF formalism) for Hydrazoic acid (HN3), a highly sensitive liquid energetic material, is reported. The force field accurately reproduces results of density functional theory (DFT) calculations. The quality and performance of the force field are examined by detailed comparison with DFT calculations related to uni, bi and trimolecular thermal decomposition routes. Reactive molecular dynamics (RMD) simulations are performed to reveal the initial chemical events governing the detonation chemistry of liquid HN3. The outcome of these simulations compares very well with recent results of tight-binding DFT molecular dynamics and thermodynamic calculations. Based on our RMD simulations, predictions were made for the activation energies and volumes in a broad range of temperatures and initial material compressions. [Preview Abstract] |
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