Abstract
Thermodynamic pathways and reaction initiation mechanisms of shocked TNT (2, 4, 6-trinitrotoluene, formula C6H2(NO2)3CH3) with shock velocities in the range of 6 -10 km⋅s-1 using the first-principles-based ReaxFF reactive force field molecular dynamics and the multiscale shock technique (MSST) are reported in this paper. The decomposition reactions occur at a shock velocity of 7 km⋅s-1 or higher. The shock initiation pressure, 25.1 GPa, is obtained from Rankine−Hugoniot relation. According to the link between macroscopic shock initiation and microscopic chemical reaction events, the formation of TNT-dimer and decomposition to C7H5O5N3 are the dominant initial route for shock induced reaction initiation. At shock speeds equal to or higher than 8km⋅s-1, TNT-dimer is formed and subsequently decomposed to C7H5O5N3, NO2 and NO. The quantity of NO2 molecules reaches maximum when TNT molecules decompose completely. Furthermore, when NO2 molecules are consumed fully, the volume of reaction system begins to expand. TNT molecules are dimerized at each shock condition, and the quantity of dimers is the largest at a shock initiation velocity of 7 km⋅s-1. Finally, the formation and evolution of carbon-containing clusters in shocked TNT are analyzed.
Highlights
Understanding of the physical and chemical issues of energetic materials in extreme conditions is involved in military field, and important in the mining industry
Shock wave parameters of various traditional high explosives and their compounds were obtained by reflected shock experiments.1 2, 4, 6-trinitrotoluene (TNT) it is best known as a high explosive material with low sensitivity properties, and can be used in warhead and cocrystallization to decrease the sensitivity of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaiso wurtzitane (CL-20)
Results shows that the higher shock velocities, the faster decomposition and heat release of shocked TNT
Summary
Understanding of the physical and chemical issues of energetic materials in extreme conditions is involved in military field (warhead, rocket propellant, etc.), and important in the mining industry. The C-NO2 homolysis is the kinetically favored initial pathway for shock initiation of TNT.4 This is mainly due to the different control mechanisms in shock and impact sensitivity. For shock-induced reaction initiation in TNT, a large number of dimers were experimentally observed. ReaxFF MD simulations have been applied to study shear reactive dynamics, influence of dislocations on shock sensitivity, thermal decomposition, thermal shock and shock initiation or detonation of energetic materials.. Shock-induced reaction initiation in TNT single crystal was simulated using reactive MD and MSST. The information of parameters, products and pathways can help the understanding of the TNT shock initiation at atomistic level and the link between macroscopic shock initiation phenomena and microscopic reaction mechanisms
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