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

2. 3% EM performance is proportional to crystal density!
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
Rao Surapenani, ARDEC

3. 20 YEARS! Millions of $$$ Low density! Octanitrocubane
Idea: Fully nitrate cubane!
High energy content
High density
High Nitrogen Energetic Materials (EMs)
Explosive energy derived from nitrogen instead of oxidation of carbon
Low signatures from combustion or detonation
Major combustion/explosion product is gaseous nitrogen
Types of High-Nitrogen EMs
All-nitrogen :
Expected energy output: 8 x TNT
Only product is nitrogen gas
Significant challenge: Stabilization at room conditions
High-nitrogen without oxidizing groups:
High specific impulse (good propelling charge)
Insufficient energy release compared to conventional explosives
High-nitrogen with strongly oxidizing groups
Adequate explosive energy in comparison with conventional explosives
Sensitivity issues
Performance expectations were
not met!
SUPER
EXPLOSIVE!!!
Low density!
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
Virtual Design
New Energetic Materials
Energetic Formulations
“Computational Toolkit”
Disruptive Energetics ·QM characterization of non-conventional energetics ·Release of stored energy in ND ·Dynamic response of shocked poly-N
Multiscale Response of Energetic Materials
Development of meso-scale models of heterogeneous EM
Development of models relating hot spot dynamics to microstructure
Bottom-up meso-particle dynamics models
Virtual testing of EM in munitions
Note that Disruptives deliverables could be supported under this RA or under the Disruptives Energetics RA
Approved for public release: distribution unlimited

6. Computational toolbox
Ionic materials
rms: 4.0%
Neutral materials
rms: 3.6%
Crystal Densities
Neutral molecules refit to improve the RMS error to 2.9%!
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)
e rich
e poor
Mapping out e- Density
Electrostatic Potential
CL20 +
Heats of Formation
Neutral materials
rms < 6 kcal/mol
Ionic materials
rms error (kcal/mol)
Comments
25.0
Requires knowledge of crystal structure
24.0
Requires QM information of single molecule!
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, ; 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),
Approved for public release. Distribution is unlimited Presented under the auspices of DEA 1060

7. Non-expert User Toolkit
Computational Toolbox
David Chavez (LANL)
Phil Leonard (LANL)
Phil Pagoria (LLNL)
Damon Parrish (NRL)
Jeff Deschamps (NRL)
Ripu Malholtra (SRI)
David Tevaul (ECBC)
Tom Klapotke (LMU)
Al Stern (NSWC)
Matt Sherrill (ARL)
Reddy Damavarapu (ARDEC)
Michael Miller (ARDEC)
BNDD
r(g/cc) = (1.870)
DHs (kcal/mol) = (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). 
Matt is our control. If it works for Matt, it will work for anyone
“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”)!

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

9. Temperature and stress is important (MD)
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 UNCLASSIFIED 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 Maximum Error Edge lengths: 0.83% Cell angles: 0.24%
SAPT Potential
Experiment
Maximum Error
Edge lengths: %
Cell angles: %
Density: %
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
RDX
HMX
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. “What is the state of the art?”
Motivation
Quantum Mechanics Is Foundation Of Our Program!
“What is the state of the art?”
Atomistic
Subgrain
Single crystal
Polycrystal
Continuum
The number of different approaches
New density functionals
Virtual orbital approaches
Pseudopotential methods
Empirical Corrections
Different benchmark systems

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

19. What is “best” option for advancing the needs of the Army?
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