Density-Dependent Liquid Nitromethane Decomposition: Molecular Dynamics Simulations Based on ReaxFF

The decomposition mechanism of hot liquid nitromethane at various compressions was studied using reactive force field (ReaxFF) molecular dynamics simulations. A competition between two different initial thermal decomposition schemes is observed, depending on compression. At low densities, unimolecul...

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Bibliographic Details
Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2011-09, Vol.115 (36), p.10181-10202
Main Authors: Rom, Naomi, Zybin, Sergey V., van Duin, Adri C. T., Goddard, William A., Zeiri, Yehuda, Katz, Gil, Kosloff, Ronnie
Format: Article
Language:English
Subjects:
A: Kinetics, Spectroscopy
Compressing
Decomposition reactions
Density
Diffusion
Dynamics
Fragments
Hot Temperature
Liquids
Methane - analogs & derivatives
Methane - chemistry
Molecular dynamics
Molecular Dynamics Simulation
Nitroparaffins - chemistry
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Summary:The decomposition mechanism of hot liquid nitromethane at various compressions was studied using reactive force field (ReaxFF) molecular dynamics simulations. A competition between two different initial thermal decomposition schemes is observed, depending on compression. At low densities, unimolecular C–N bond cleavage is the dominant route, producing CH3 and NO2 fragments. As density and pressure rise approaching the Chapman–Jouget detonation conditions (∼30% compression, >2500 K) the dominant mechanism switches to the formation of the CH3NO fragment via H-transfer and/or N–O bond rupture. The change in the decomposition mechanism of hot liquid NM leads to a different kinetic and energetic behavior, as well as products distribution. The calculated density dependence of the enthalpy change correlates with the change in initial decomposition reaction mechanism. It can be used as a convenient and useful global parameter for the detection of reaction dynamics. Atomic averaged local diffusion coefficients are shown to be sensitive to the reactions dynamics, and can be used to distinguish between time periods where chemical reactions occur and diffusion-dominated, nonreactive time periods.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp202059v