Simulations of Thin Flyer Plate Shock Experiments Using ReaxFF:

Applications to PETN, RDX, HMX and TATB

Luzheng Zhang, Siddharth Dasgupta, Adri vanDuin, Alejandro Strachan†, and William A. Goddard

Materials and Process Simulation CenterCalifornia Institute of Technology

†Theoretical Division, Los Alamos National Laboratory

ASCI Site Visit Meeting, October 28-29, 2003

HE Flyer Plate Simulations

1. Equilibrate: NVT for 10 ps at 300K for crystal structure;2. Apply x% uniaxial compression @ > detonation velocity = V(100-x)%;3. NVE for 1 ps at compressed volume;4. Apply x% uniaxal expansion at same velocity = V(100 + x)%;5. NVE for 4 ps at expanded volume.

NVE ~4 ps

V(100 +x) % expansion

V(100-x) % compression - > detonation velocity

~0.15ps ~1 ps

NVE ~1 ps

Fast compressionàrelaxationàmild expansionàrelaxation

Systems – Shock Axis in Red

46416(13.26 × 13.26 × 26.80)PETN(001)

48816(15.14 × 23.89 × 11.82)α-HMX

33616(26.36 × 11.57 × 10.71)RDX

46416(26.52 × 13.26 × 13.40)PETN(110)

38416(18.02 × 9.02 × 27.24)TATB

67224(30.8 0× 15.40 × 32.55)δ-HMX

47216+8 H2O(26.54 × 15.80 × 10.95)γ-HMX

488

atoms

16

molecules

(26.16 × 11.05 × 17.40)

unit cell (a × b × c), Å

β-HMX

HE

PETN : Temperature

The simulation box is compressed by 30%, 40%, 50% followed by 1-ps NVE, and then expanded to 130%, 140%, and 150% within ~1 ps, followed by 4-ps NVE.

Detonation T = 3400K, P = 32 GPa at 1.77 g/cc.

PETN (110)

0

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0.0 1.0 2.0 3.0 4.0 5.0 6.0

Time, ps

Tem

pera

ture

, K

x=50%

x=40%

x=30%

PETN (001)

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4000

6000

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0.0 1.0 2.0 3.0 4.0 5.0 6.0

Time, psT

emp

erat

ure

, K

x=50%

x=40%

x=30%

Compression NVE Expansion NVE after expansion

PETN: Degree of Completion

C5H8N4O12 à 2N2 + 4H2O + 3CO2 + 2CO; 16 PETN à 176 product molecules

The simulation box is compressed by 30%, 40%, 50% followed by 1-ps NVE, and then expanded to 130%, 140%, and 150% within ~1 ps, followed by 4-ps NVE.

PETN (110)

0

20

40

60

80

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180

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

Time, ps

To

tal s

pec

ies

x=50%

x=40%

x=30%

PETN (001)

0

20

40

60

80

100

120

140

160

180

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

Time, ps

To

tal s

pec

ies

x=50%

x=40%

x=30%

Final Configuration and Pressure for PETN(110)

X=013.7 GPa

X=30%11.54 GPa

X=40%18.1 GPa

X=50%56.6 GPa

Experimental detonation T = 3400K, P = 32 GPa at 1.77 g/cc.

Final Configuration and Pressure for PETN(001)

Experimental detonation T = 3400K, P = 32 GPa at 1.77 g/cc.

X=08.5 GPa

X=30%9.4 GPa

X=40%58.1 GPa

X=50%78.4 GPa

PETN: Specie Analysis

PETN(110)

0

5

10

15

20

25

30

35

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0Time, ps

Nu

mb

er o

f sp

ecie

s

H2O

CO

CO2

N2

NO2

NO

NO3

OH

O2

PETN

PETN(001)

0

5

10

15

20

25

30

35

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0Time, ps

Nu

mb

er o

f sp

ecie

s

H2O

CO

CO2

N2

NO2

NO

NO3

OH

O2

PETN

HMX : Temperature

Detonation T = 2365K, P = 39.2 GPa at 1.90 g/cc.

x=30% x=40%

0

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0.0 1.0 2.0 3.0 4.0 5.0 6.0

Time, ps

Tem

per

atu

re, K

alpha-HMX

beta-HMX

delta-HMX

gamma-HMX

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0.0 1.0 2.0 3.0 4.0 5.0 6.0

Time, ps

Tem

per

atu

re, K

alpha-HMXbeta-HMXdelta-HMXgamma-HMX

HMX: Degree of Completion

C4H8N8O8 à 4N2 + 4H2O + 4CO; 16 HMX à 192 product molecules

x=30% x=40%

0

50

100

150

200

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Time, ps

To

tal s

pec

ies

alpha-HMXbeta-HMXdelta-HMXgamma-HMX

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0.0 1.0 2.0 3.0 4.0 5.0 6.0

Time, ps

Tem

per

atu

re, K

alpha-HMX

beta-HMX

delta-HMX

gamma-HMX

RDX:Temperature & Degree of Completion

Detonation T = 2793K, P = 33.8 GPa at 1.77 g/cc.

C3H6N6O6 à 3N2 + 3H2O + 3CO; 16 RDX à 144 product molecules

The simulation box is compressed by 30%, 40%, 50% followed by 1-ps NVE, and then expanded to 130%, 140%, and 150% within ~1 ps, followed by 4-ps NVE.

RDX

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0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

Time, ps

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atu

re, K

x=50%

x=40%

x=30%

RDX

0

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60

90

120

150

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

Time, ps

To

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pec

ies

x=50%

x=40%

x=30%

TATB Temperature & Degree of Completion

Detonation P = 29 GPa at 1.89 g/cc

C6H6N6O6 à 3N2 + 3H2O + 3CO + 3C; 16 TATB à 192 product molecules

The simulation box is compressed by 30% and 40% followed by 1-ps NVE, and then expanded to 130% and 140% within ~1 ps, followed by 4-ps NVE.

TATB

0

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0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

Time, ps

Tem

per

atu

re, K

x=40%

x=30%

TATB

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90

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150

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

Time, psT

ota

l sp

ecie

s

x=40%

x=30%

• HE (PETN,HMX,RDX, and TATB) sensitivity is tested by Flyer Plate impact MD simulations with the ReaxFF.

• At constant compression/expansion ratios, degree of completion for impact induced reactions increases in this order: TATB<PETN<HMX<RDX.

• Among HMX at different phases, δ-HMX is the most sensitive, which agrees with experimental results.

• The flyer plate impact simulations are being applied to other HEs, e.g. CL20, DMN, etc.

Conclusions

This work is funded by the Department of Energy