Molecular Dynamics Study of the Effect of H₂O on the Thermal Decomposition of α Phase CL-20

Abstract

The response of the mechanisms of the α polymorph of CL-20 (α-CL-20) to high temperature is important for understanding the phenomenon of shock initiation, shock ignition, and detonation. The thermal decomposition of α-CL-20 hydrate and pure α-CL-20 were studied by ReaxFF reactive molecular dynamics simulations to obtain the time evolution of water molecules and the effect of H2O on the mechanisms of CL-20 at high temperatures. It was determined that the initial decomposition mechanisms of CL-20 are not dependent on the presence of water, but the secondary reaction pathways are. At low temperatures (T<1500 K), there is no relationship between the H2O, hydrate CL-20, and pure CL-20 systems, as the mechanism is only the dissociation of the N-NO2 bond to form the NO2 radical. At high temperatures (1500 K≤T≤2500 K), water molecules act as a reactant or form catalytic systems with NO2 radical to form OH radical, leading to the formation of O2, H2O2, and other products. Water molecules accelerate the secondary stage reaction of hydrate systems, leading to increased secondary reaction rates and number of NO2 radicals in the CL-20 hydrate compared with the pure CL-20 system. At very high temperatures (T>2500 K), the dissociation of water molecules competes with the initial thermal decomposition pathway of CL-20, leading to a larger rate constant for the pure CL-20 than for the hydrate CL-20.

Molecular Dynamics Simulations on the Thermal Decomposition of Meta-Aramid Fibers

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The Mitigation Effect of Synthetic Polymers on Initiation Reactivity of CL-20: Physical Models and Chemical Pathways of Thermolysis

“…It enables the simulation of HEM under realistic conditions in a computationally efficient way . Thus, ReaxFF could describe both the gas phase chemistry of hydrocarbons and various C–H–N-O energetic systems, including the derived decomposition pathways of RDX. , It has been widely used in simulation of chemical pathways of high energetic materials decomposition, where “HE” force field was especially configured and used for nitramines. , Another more suitable force field called “CHONSSi-lg” was developed recently for explosives based on “HE” force field considering London Dispersion, which does not take into account of force field of fluorine. In order for a better comparison, all of the involved materials have been simulated under extremely fast heating (300 K/ps) by using a “TiOCHNCl”, which is suitable for both C–H–N–O based energetic materials and polymers including hydrocarbons and fluoropolymers .…”