Thermal decomposition of solid phase nitromethane under various heating rates and target temperatures based on ab initio molecular dynamics simulations
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The Car-Parrinello molecular dynamics simulation was applied to study the thermal decomposition of solid phase nitromethane under gradual heating and fast annealing conditions. In gradual heating simulations, we found that, rather than C–N bond cleavage, intermolecular proton transfer is more likely to be the first reaction in the decomposition process. At high temperature, the first reaction in fast annealing simulation is intermolecular proton transfer leading to CH3NOOH and CH2NO2, whereas the initial chemical event at low temperature tends to be a unimolecular C–N bond cleavage, producing CH3 and NO2 fragments. It is the first time to date that the direct rupture of a C–N bond has been reported as the first reaction in solid phase nitromethane. In addition, the fast annealing simulations on a supercell at different temperatures are conducted to validate the effect of simulation cell size on initial reaction mechanisms. The results are in qualitative agreement with the simulations on a unit cell. By analyzing the time evolution of some molecules, we also found that the time of first water molecule formation is clearly sensitive to heating rates and target temperatures when the first reaction is an intermolecular proton transfer.
KeywordsThe intermolecular proton transfer reaction C–N bond cleavage Ab initio molecular dynamics simulations PACS 71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations 82.30.-b Specific chemical reactions Reaction mechanisms 82.30.Cf Atom and radical reactions Chain reactions Molecule–molecule reactions 82.20.Kh Potential energy surfaces for chemical reactions
This work is supported by grants from the National Natural Science Foundation of China (Grant Nos. 11174201, 11174214, 11204192), the National Key Laboratory Fund for Shock Wave and Detonation Physics Research of the China Academy of Engineering Physics (Grant Nos. 2012-Zhuan-08, 9140C671101110C6709), the National Basic Research Program of China (Grant Nos. 2010CB731600, 2011CB808201), the Defense Industrial Technology Development Program of China (Grant No. B1520110002), and the State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology (Grant No. KFJJ12-2Y).
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