UNCLASSIFIED
U.S. Army Research, Development and Engineering Command
Intermolecular Forces in Army Research
DeCarlos E. Taylor
August 2, 2012
UNCLASSIFIED
EM Design
Candidate EM
PROPERTIES
Computer
Model
Quantum
Mechanics
• Structure
• Heat of formation
• Density
• Decomposition pathways
• Mechanical properties
• Shock response
• Thermal stability
• Sensitivity
EM performance is proportional to crystal density!
Detonation Velocity
D=a+b*ρ
Detonation Pressure
P ~ ρ * D2
3%
Rao Surapenani, ARDEC
Octanitrocubane
20 YEARS!
Millions of $$$
Idea: Fully nitrate cubane!
•High energy content
• High density
SUPER
EXPLOSIVE!!!
Low density!
Approved for public release: distribution unlimited
Performance
expectations were
not met!
QM Methods in Army Research
Semiempirical
NDDO (AM1, PM3, MNDO/d)
Perturbation Theory
MBPT(2), SAPT
Quantum
Mechanics
Coupled Cluster Theory
CCSD, CCSD(T), EOM
UNCLASSIFIED
Density Functional Theory
Computational Research in EMs
Virtual Design
•New Energetic Materials
• Energetic Formulations
• “Computational Toolkit”
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
Disruptive Energetics
·QM characterization of non-conventional energetics
·Release of stored energy in ND
·Dynamic response of shocked poly-N
Approved for public release: distribution unlimited
Theoretical Molecular Vo
300
Computational toolbox
200
100
(a)
0
500
400
300
200
100
Experimental Molecular Volume (Å3)
0
Crystal Densities
2.2
• 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)
Theoretical Density (g/cc)
Neutral materials
rms: 3.6%
1.8
2.0
Ionic materials
rms: 4.0%
1.6
1.4
1.8
1.2
1.6
1.0
1.4
0.8
(b)
1.2
1.2
CL20
Mapping out e Density
2.0
1.8
1.6
1.4
Experimental Density (g/cc)
2.2
0.6
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Neutral molecules refit to improve the RMS error to 2.9%!
+
Heats of Formation
150
Electrostatic Potential
e rich
e poor
Calculated Values (kcal/mol)
100
Neutral materials
rms < 6 kcal/mol
Ionic materials
50
0
-50
rms error
(kcal/mol)
Comments
25.0
Requires knowledge of
crystal structure
24.0
Requires QM information
of single molecule!
-100
-150
-200
-250
-250 -200 -150 -100
-50
0
50
100
150
Experimental Values (kcal/mol)
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
Computational Toolbox
David Chavez (LANL)
BNDD
Phil Leonard (LANL)
r(g/cc) = 1.914 (1.870)
DHs (kcal/mol) = 145.1 (142)
Phil Pagoria (LLNL)
Damon Parrish (NRL)
Jeff Deschamps (NRL)
Ripu Malholtra (SRI)
3,6-Bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazene (BNDD): A Powerful Sensitive
David Tevaul (ECBC)
Explosive. Leonard, Philip W. Pollard, Colin J; Chavez, David E.; Rice, Betsy M. Parrish, Damon
Tom Klapotke (LMU)
A. SYNLETT 14 ,2097 (2011).
Al Stern (NSWC)
Matt Sherrill (ARL)
Reddy Damavarapu (ARDEC)
“Have I told you lately how much
I LOVE the new script! It makes
Michael Miller (ARDEC)
everything so much easier!
Thanks! You are the best!”
12/12/2011
Non-expert User Toolkit
(Designed by Ed Byrd)
1. Simple Input (xyz)
2. Submit one job, answers pop out.
3. 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
Disruptive Energetics
Polymeric CO
Polymeric Nitrogen
Nanodiamonds
Surface reconstruction
15 GPa
New polymeric
crystalline phase!
High Velocity Collisions
UNCLASSIFIED
Hexanitrobenzene
Fox-7
DATB
Trinitrobenzene
Trinitrotoluene
Energetic Molecular Crystals
TATB
•Large unit cells
• Condensed phase
(periodicity)
• Temperature and stress
is important (MD)
Trinitroaniline
DFT – Energetic Molecular Crystals
3% Maximum Allowable Error
UNCLASSIFIED
Dispersion - TATB
SAPT Interaction Energy
Electrostatic=-4.89
Induction=-5.301
Dispersion=-16.47
Total=-10.05
SAPT Interaction Energy
Electrostatic=-5.43
Induction=-7.87
Dispersion=-22.47
Total=-11.65
SAPT Interaction Energy
Electrostatic=-3.87
Induction=-2.16
Dispersion=-5.12
Total=-4.80
UNCLASSIFIED
SAPT Interaction Energy
Electrostatic=0.44
Induction=-2.68
Dispersion=-8.52
Total=-3.60
SAPT Interaction Energy
Electrostatic=-4.63
Induction=-3.08
Symmetry Adapted Perturbation Theory
Dispersion=-7.57
Total=-5.93
• Fit intermolecular potential (exp-6)
• 900 ab initio
data points
SAPT Interaction
Energy
Electrostatic=-4.07
• Minima on fitted surface analyzed with
Induction=-1.84
ab initio SAPT(DFT)
Dispersion=-4.06
Total=-4.47
SAPT Interaction Energy
Electrostatic=-4.47
Induction=3.71
Dispersion=-9.22
Total=-6.09
UNCLASSIFIED
Dispersion Corrections
SOFTWARE
• CP2K
• VASP
Dispersion Corrected Atom-centered Potentials (DCACPS)
DFT-D* (Grimme)
Fitted to CCSD(T)
interaction energies
UNCLASSIFIED
DCACPS – Energetic Molecular Crystals
RDX
TATB
HMX
PETN
UNCLASSIFIED
% error in density
Ambient pressure ionic high nitrogen EMs
UNCLASSIFIED
DFT-D Energetic Molecular Crystals
TATB
HMX
PETN
UNCLASSIFIED
Motivation
Quantum Mechanics Is Foundation Of Our Program!
Continuum
“What is the state of the art?”
Polycrysta
l
• The
number of different approaches
Single
crysta
l
Subgrain
New density functionals
Virtual orbital approaches
Pseudopotential methods
Empirical Corrections
Atomisti
c
• Different
benchmark systems
Imidazole
Water
Nitromethane
4.5
Nitrobenzene
R (Ang)
6.5
Benzene-Methane
10.5
-2
CCSD(T)
-3
CBS
-6
-7
12
-2
-1
-5
8 R(Ang) 10
0
0
-4
Ethanol
Fox-7
6
8.5
Benzene-Water
EDNA
Energy(kcal/mol)
Energy(kcal/mol)
2.5
Methyl Formate
-4
CCSD(T)
-6
CBS
-8
-10
-12
-14
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