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UNCLASSIFIED

UNCLASSIFIED. Intermolecular Forces in Army Research DeCarlos E. Taylor August 2, 2012. UNCLASSIFIED. EM Design. Candidate EM. PROPERTIES Structure Heat of formation Density Decomposition pathways Mechanical properties Shock response Thermal stability Sensitivity .

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UNCLASSIFIED

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  1. UNCLASSIFIED Intermolecular Forces in Army Research DeCarlos E. Taylor August 2, 2012 UNCLASSIFIED

  2. EM Design Candidate EM • PROPERTIES • Structure • Heat of formation • Density • Decomposition pathways • Mechanical properties • Shock response • Thermal stability • Sensitivity Quantum Mechanics Computer Model EM performance is proportional to crystal density! 3% Detonation Velocity D = a + b * ρ Detonation Pressure P ~ ρ * D2 RaoSurapenani, ARDEC

  3. Octanitrocubane 20 YEARS! Millions of $$$ • Idea: Fully nitrate cubane! • High energy content • High density Performance expectations were not met! Low density! SUPER EXPLOSIVE!!! Approved for public release: distribution unlimited

  4. QM Methods in Army Research Semiempirical NDDO (AM1, PM3, MNDO/d) Perturbation Theory MBPT(2), SAPT Quantum Mechanics Density Functional Theory Coupled Cluster Theory CCSD, CCSD(T), EOM UNCLASSIFIED

  5. Computational Research in EMs Approved for public release: distribution unlimited

  6. Computational toolbox + Mapping out e- Density CL20 • Using quantum mechanics, we have derived correlations to solid phase heats of formation and crystalline densities for both neutral and ionic energetic materials • Correlations require calculations only on single molecule (not bulk material) Electrostatic Potential Neutral materials rms: 3.6% e poor e rich Crystal Densities Heats of Formation Neutral materials rms < 6 kcal/mol Ionic materials Ionic materials rms: 4.0% Neutral molecules refit to improve the RMS error to 2.9%! E. F. C. Byrd and B. M. Rice, “Improved Prediction of Heats of Formation of Energetic Materials Using Quantum Mechanical Calculations”, Journal of Physical Chemistry A (2006) 110, 1005-1013; ibid (2009) 113, 5813. B. M. Rice and E. F. C. Byrd, “Accurate predictions of crystal densities using quantum mechanical molecular volumes”, Journal of Physical Chemistry A (2007) 111(42), 10874-1087 Approved for public release. Distribution is unlimited. Presented under the auspices of DEA 1060

  7. Computational Toolbox David Chavez (LANL) Phil Leonard (LANL) Phil Pagoria (LLNL) Damon Parrish (NRL) Jeff Deschamps (NRL) RipuMalholtra (SRI) David Tevaul (ECBC) Tom Klapotke (LMU) Al Stern (NSWC) Matt Sherrill (ARL) Reddy Damavarapu(ARDEC) Michael Miller (ARDEC) BNDD r(g/cc) = 1.914 (1.870) DHs (kcal/mol) = 145.1 (142) 3,6-Bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazene (BNDD): A Powerful Sensitive Explosive. Leonard, Philip W. Pollard, Colin J; Chavez, David E.;Rice, Betsy M.Parrish, Damon A.SYNLETT 14 ,2097 (2011).  “Have I told you lately how much I LOVE the new script! It makes everything so much easier! Thanks! You are the best!” 12/12/2011 Non-expert User Toolkit (Designed by Ed Byrd) Simple Input (xyz) Submit one job, answers pop out. Write paper and wow your friends with your theoretical acumen. We have a special DSRC account for you to use (“The Sandbox”)! Matt is our control. If it works for Matt, it will work for anyone

  8. Disruptive Energetics Polymeric Nitrogen Polymeric CO Nanodiamonds Surface reconstruction New polymeric crystalline phase! 15 GPa High Velocity Collisions

  9. UNCLASSIFIED Hexanitrobenzene Fox-7 DATB Trinitrobenzene Trinitrotoluene Energetic Molecular Crystals TATB Trinitroaniline • Large unit cells • Condensed phase • (periodicity) • Temperature and stress • is important (MD)

  10. DFT – Energetic Molecular Crystals 3% Maximum Allowable Error UNCLASSIFIED

  11. Dispersion - TATB SAPT Interaction Energy Electrostatic=0.44 Induction=-2.68 Dispersion=-8.52 Total=-3.60 SAPT Interaction Energy Electrostatic=-4.89 Induction=-5.301 Dispersion=-16.47 Total=-10.05 SAPT Interaction Energy Electrostatic=-4.63 Induction=-3.08 Dispersion=-7.57 Total=-5.93 SAPT Interaction Energy Electrostatic=-5.43 Induction=-7.87 Dispersion=-22.47 Total=-11.65 • Symmetry Adapted Perturbation Theory • Fit intermolecular potential (exp-6) • 900 ab initio data points • Minima on fitted surface analyzed with ab initio SAPT(DFT) SAPT Interaction Energy Electrostatic=-4.07 Induction=-1.84 Dispersion=-4.06 Total=-4.47 SAPT Interaction Energy Electrostatic=-3.87 Induction=-2.16 Dispersion=-5.12 Total=-4.80 SAPT Interaction Energy Electrostatic=-4.47 Induction=3.71 Dispersion=-9.22 Total=-6.09 UNCLASSIFIED

  12. Fox-7 SAPT Potential Experiment Maximum Error Edge lengths: 0.83% Cell angles: 0.24% Density: 0.37% UNCLASSIFIED

  13. Dispersion Corrections • SOFTWARE • CP2K • VASP Dispersion Corrected Atom-centered Potentials (DCACPS) DFT-D* (Grimme) CCSD(T) Fitted to CCSD(T) interaction energies UNCLASSIFIED

  14. DCACPS – Energetic Molecular Crystals HMX RDX PETN TATB UNCLASSIFIED

  15. Ambient pressure ionic high nitrogen EMs % error in density UNCLASSIFIED

  16. DFT-D Energetic Molecular Crystals TATB HMX PETN UNCLASSIFIED

  17. Motivation Quantum Mechanics Is Foundation Of Our Program! “What is the state of the art?” • The number of different approaches Virtual orbital approaches New density functionals Pseudopotential methods Empirical Corrections • Different benchmark systems Polycrystal Continuum Atomistic Single crystal Subgrain

  18. Coupled Cluster Benchmarks Benzene-Methane Water Benzene-Water Ethanol Imidazole Methyl Formate Nitromethane Nitrobenzene EDNA Fox-7 2 Million CPU Hours

  19. Discussion What is “best” option for advancing the needs of the Army? • Density Functionals vs. Empirical Corrections C6R-6 corrections do not change electronic structure • “…all non-empirical attempts to introduce van der Waals interaction in DFT will finally end up with methods that will be at least at compex as the simplest wavefunction methods.” • Perspectives on application to large systems

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