Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session U3: First-Principles and Molecular Dynamics Calculations IX: Energetic Materials III |
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Chair: Maija Kukla, National Science Foundation Room: Renaissance Ballroom AB |
Thursday, June 30, 2011 2:00PM - 2:15PM |
U3.00001: Effect of pressure on nitramine dissociation: A density-functional theory study Igor Schweigert The effect of increased pressure on the initial pathways and kinetics of dimethylnitramine dissociation is studied using density-functional theory (DFT). Two competitive pathways, radical NO$_2$ elimination and concerted HONO elimination, are evaluated using atomic basis, hybrid DFT thermochemistry and planewave DFT molecular dynamics. The computed thermochemistry and reactive dynamics of condensed-phase dissociation are contrasted with those in the gas phase. These results are discussed in the context of developing a reduced chemical model of nitramine decomposition suitable for inclusion in mesoscale simulations. [Preview Abstract] |
Thursday, June 30, 2011 2:15PM - 2:30PM |
U3.00002: MD simulation of condense phase detonation using a Moving Window technique Mikalai Budzevich, Vasily Zhakhovsky, Carter White, Ivan Oleynik The structure of steady detonation waves in solid energetic material (EM) was investigated using a newly developed Moving Window molecular dynamics (MW-MD) technique. The unique feature of this method is its decoupling of simulation time from the propagation distance, which allows us to simulate the steady regime of detonation. The MW-MD technique is applied to the modified AB model of a detonating EM. The standard AB model involves very fast chemical reactions, which lead to a very narrow reaction zone. Therefore, the parameters of the AB model were modified to produce a reaction zone width comparable with the transverse dimension of the sample. The structure of the detonation front and associated atomic-scale processes are discussed. [Preview Abstract] |
Thursday, June 30, 2011 2:30PM - 2:45PM |
U3.00003: Molecular Dynamics Simulations of Hot Spots and Detonation on the Roadrunner Supercomputer Susan Mniszewski, Marc Cawkwell, Timothy Germann The temporal and spatial scales intrinsic to a \textit{real} detonating explosive are extremely difficult to capture using molecular dynamics (MD) simulations. Nevertheless, MD remains very attractive since it allows for the resolution of dynamic phenomena at the atomic scale. We have studied the effects of spherical voids on the build up to detonation in three dimensions (3D) in a \textit{model} explosive using the reactive empirical bond order (REBO) potential for the A-B system. This force field is attractive because it has been shown to support a detonation while being simple, analytic, and short-ranged. The transition from 2D to 3D simulations was facilitated by our port of the REBO force field in the parallel MD code SPaSM to LANL's petaflop Roadrunner supercomputer based on previous work by Swaminarayan and Germann [T. C. Germann et al. Concurrency Computat.: Pract. Exper. \textbf{21}, 2143 (2009)]. We will provide a detailed discussion of the challenges associated with computing interatomic forces on a hybrid Opteron/Cell BE computational architecture. We will compare and contrast our results in 3D from Roadrunner with earlier 2D simulations of hot-spot assisted detonations by Heim, Herring, and co-workers [S. D. Herring et al. Phys. Rev. B, \textbf{82}, 214108 (2010)]. [Preview Abstract] |
Thursday, June 30, 2011 2:45PM - 3:00PM |
U3.00004: Nonequilibrium molecular dynamics simulations of aluminum oxynitride N. Scott Weingarten, Iskander G. Batyrev, Betsy M. Rice Aluminum oxynitride, or AlON, is a crystalline ceramic material, whose transparency and high strength make it a potentially useful material for many structural engineering applications. The structure of AlON is cubic spinel, with anions forming a close-packed structure, and aluminum atoms occupying the tetrahedral and octahedral interstitial sites, with one site remaining vacant. However, the location of the vacancy is not unique, nor are the positions of the nitrogen atoms, which replace oxygen atoms in the close-packed structure. We have developed an interatomic potential based on the Buckingham model for use in classical molecular dynamics (MD) simulations of AlON. Using this model, and crystal structures determined from first principles calculations, we have calculated a number of material properties and we compare these to experimental values. We present the results of nonequilibrium MD simulations of single crystal and bicrystal AlON systems under applied tension and compression, with a discussion of the yield and failure mechanisms of this material. Finally, we present preliminary observations of shock simulations, with comparisons to simulations of other crystalline ceramic material. [Preview Abstract] |
Thursday, June 30, 2011 3:00PM - 3:15PM |
U3.00005: Comparative analysis of the data on shocked benzene properties obtained in MD simulations with different interatomic potentials Vladimir Dremov, Gennady Ionov, Filipp Sapozhnikov, Ilya Derbenev, Jean-Bernard Maillet, Nikolas Pinot, Laurent Soulard We present in the paper the results of reactive MD simulations of shock loading of liquid benzene. The Hugoniot of benzene was calculated with the hugoniostat technique in the pressure range 0-100 GPa. The AIREBO potential was used as the model of interatomic interactions. The number of benzene molecules in the simulation was about 1000. Timescale of the MD simulation for each Hugoniot point is several nano-seconds. Obtained results were compared with the experimental ones and with simulation results obtained early with ReaxFF and LCBOPII potentials. The key questions under investigation are the kinetics of polymerization at moderate pressures (10-20 GPa) and the kinetics of the formation of condensed carbon clusters at high pressures ($>$40 GPa). The AIREBO was tested from the point of view of minimal model adequately reproducing the properties of shock compressed hydrocarbons. [Preview Abstract] |
Thursday, June 30, 2011 3:15PM - 3:30PM |
U3.00006: Self-consistent Tight-binding Molecular Dynamics Simulations of Shock-induced Reactions in Hydrocarbons Marc Cawkwell, Edward Sanville, Anders Niklasson, Stephen Sheffield, Dana Dattelbaum Shock-induced reactions in liquid hydrocarbons have been studied using quantum-based, self-consistent tight-binding (SC-TB) molecular dynamics simulations with an accurate and transferable model for interatomic bonding. Our SC-TB code LATTE enables explicit simulations of shock compression using the universal liquid Hugoniot. Furthermore, the effects of adiabatic shock heating are captured precisely using Niklasson's energy conserving extended Lagrangian Born-Oppenheimer Molecular Dynamics formalism. We have been able to perform relatively large-scale SC-TB simulations by either taking advantage of the sparsity of the density matrix to achieve $O(N)$ performance or by using graphical processing units to accelerate $O(N^{3})$ algorithms. Simulations of liquid methane, benzene, and tert-butylacetylene are used to illustrate these capabilities. In particular, in accord with recent experiments we show that tert-butylacetylene undergoes radical chain polymerization reactions under shock compression. [Preview Abstract] |
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