Shock-Induced Hot Spot Formation and Spalling in 1,3,5-trinitroperhydro-1,3,5-triazine Containing a Cube Void

2020

ACS Omega

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In this paper, ReaxFF force field combined with molecular dynamics method was used to study the ignition, deflagration, and detonation of pentaerythritol tetranitrate (PETN) induced by hot spots. The hot spot is 5.6% of the total volume. When the hot spot temperature is 1000 K, the deflagration and detonation of PETN cannot be observed in the simulation time of 200 ps. When the hot spot temperature is 2000 K, it corresponds to the heating time of 20 to 50 ps, deflation and detonation were observed. During hot spot ignition, the products of decomposition of the condensed phase PETN are dominated by NO2 and HONO. The energy required for the C–C bond and C–ONO2 bond cleavage in PETN is high, resulting in only a small amount of CH2O and NO3 during the reaction. Small nitrogen-containing molecules (such as NO2, NO3, HONO, HNO3, etc.) mainly exist during thermal equilibrium, while the number of N2 increases sharply during the thermal runaway stage, and a small amount of NH3 and NH2 are also produced. H2O molecules are formed before CO2 and N2 are produced, and the number always dominates. During the thermal runaway, the entire system can maintain a spontaneous reaction, resulting in a sharp rise in temperature of about 2500 K in 20 ps. During this phase, the catalytic effect of H2O accelerates the formation of CO2 and N2 due to the near Chapman–Jouguet point in the crystal. PETN is a weak oxygen balance explosive that results in a small amount of CO and H2 production during the thermal instability phase. When the reaction is balanced, the relative molecular mass is close to or exceeds that of PETN. The product is only less than 1% of the total mass fraction, while the small molecule product is as high as 78%, and some relative molecular masses are [75,225]. The intermediates account for about 21%. Rapid and complex reaction events make it difficult to accurately predict the structure of these intermediates by existing experiments and calculations, which will be the focus of future research.

Section: Simulation Detailsmentioning

confidence: 96%

Analysis of Chemical Reaction Process after Pentaerythritol Tetranitrate Hot Spot Ignition

2020

ACS Omega

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“…RDX is a kind of energetic additive with good comprehensive performance because of its stable chemical property and great explosive power. In order to understand the combustion properties of RDX, related research studies [103][104][105][106][107][108] are being carried out. Peng et al 108 studied the pyrolysis process of a-RDX and its derivatives.…”

Section: Pyrolysis and Combustion Mechanism Of Rdxmentioning

confidence: 99%

Recent ReaxFF MD studies on pyrolysis and combustion mechanisms of aviation/aerospace fuels and energetic additives

Chen

Li²,

et al. 2023

Energy Adv.

“…The ReaxFF reaction force field based on the first principle can be used under extreme conditions to describe the formation and fracture of the intermolecular bonds of energetic materials , under near-real conditions through the relationship between bond length, bond level, and bond energy as well as the dynamic transfer of charges between atoms. ReaxFF/lg added a description of the London dispersion force on the basis of ReaxFF, that is, amending the long-range interaction force between molecules to more accurately describe the structure and density of molecular crystals.…”

Section: Simulation Detailsmentioning

confidence: 99%

ReaxFF Molecular Dynamics Simulation of Hydrostatic and Uniaxial Compression of Nitrate Energetic Materials

2020

ACS Omega

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The physical and chemical properties of typical nitrate energetic materials under hydrostatic compression and uniaxial compression were studied using the ReaxFF/lg force field combined with the molecular dynamics simulation method. Under hydrostatic compression, the P – V curve and the bulk modulus ( B 0 ) obtained using the VFRS equation of state show that the compressibility of the three crystals is nitroglycerine (NG) > erythritol tetranitrate (ETN) > 2,3-bis-hydroxymethyl-2,3-dinitro-1,4-butanediol tetranitrate (NEST-1). The a - and c -axis of ETN are easy to compress under the action of hydrostatic pressure, but the b -axis is not easy to compress. The b -axis of NEST-1 is the most compressible, while the a - and c -axis can be compressed slightly when the initial pressure increases and then remains unchanged afterward. The a -, b -, and c -axes of NG all have similar compressibilities. By analyzing the change trend of the main bond lengths of the crystals, it can be seen that the most stable of the three crystals is the N–O bond and the largest change is in the O–NO 2 bond. The stability of the C–O bond shows that the NO 3 produced by nitrates is not from the C–O bond fracture. Under uniaxial compression, the stress tensor component, the average principal stress, and the hydrostatic pressure have similar trends and amplitudes, indicating that the anisotropy behaviors of the three crystals ETN, NEST-1, and NG are weak. There is no significant correlation between maximum shear stress and sensitivity. The maximum shear stresses τ xy and τ yz of the ETN in the [010] direction are 1.5 GPa higher than τ xz . However, the maximum shear stress of NG shows irregularity in different compression directions, indicating that there is no obvious correlation between the maximum shear stress and sensitivity.