Thermal Decomposition of Condensed-Phase Nitromethane from Molecular Dynamics from ReaxFF Reactive Dynamics
CALIFORNIA INST OF TECH PASADENA MATERIALS AND PROCESS SIMULATION CENTER
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We studied the thermal decomposition and subsequent reaction of the energetic material nitromethane CH3NO2 using molecular dynamics with ReaxFF, a first principles-based reactive force field. We characterize the chemistry of liquid and solid nitromethane at high temperatures 2000-3000 K and density 1.97 gcu cm for times up to 200 ps. At T 3000 K the first reaction in the decomposition of nitromethane is an intermolecular proton transfer leading to CH3NOOH and CH2NO2. For lower temperatures T 2500 and 2000 K the first reaction during decomposition is often an isomerization reaction involving the scission of the C-N bond the formation of a C-O bond to form methyl nitrate CH3ONO. Also at very early times we observe intramolecular proton transfer events. The main product of these reactions is H2O which starts forming following those initiation steps. The appearance of H2O marks the beginning of the exothermic chemistry. Recent quantum-mechanics-based molecular dynamics simulations on the chemical reactions and time scales for decomposition of a crystalline sample heated to T 3000 K for a few picoseconds are in excellent agreement with our results, providing an important, direct validation of ReaxFF.
- Organic Chemistry