First-Principles-Based Reaction Kinetics for Decomposition of Hot, Dense Liquid TNT from ReaxFF Multiscale Reactive Dynamics Simulations

• Published in: Journal of physical chemistry. C Vol. 117; no. 41; pp. 21043 - 21054
• Main Authors: Rom, Naomi, Hirshberg, Barak, Zeiri, Yehuda, Furman, David, Zybin, Sergey V., Goddard, William A., Kosloff, Ronnie
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 17-10-2013
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Materials science; Methods of crystal growth; physics of crystal growth; Physics; Solubility, segregation, and mixing; phase separation; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; Carbon non metal bond; Temperature dependence; Liquid state; Growth rate; Thermal decomposition; Digital simulation; Theoretical study; Carbon; Linear model; Kinetic model; Temperature effects; Multiscale method; Phase separation; Reaction kinetics; Displacement rates; Dimers; Gas phase; Nitrogen dioxide; Activation energy; Strength functions
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp404907b

The reaction kinetics of the thermal decomposition of hot, dense liquid TNT was studied from first-principles-based ReaxFF multiscale reactive dynamics simulation strategy. The decomposition process was followed starting from the initial liquid phase, decomposition to radicals, continuing through formation of carbon-clusters products, and finally to formation of the stable gaseous products. The activation energy of the initial endothermic decomposition rate and the subsequent exothermic reactions were determined as a function of density. Analysis of fragments production in different densities and temperatures is presented. We find that unimolecular C–N bond scission dominates at the lower densities (producing NO2), whereas dimer formation and decomposition to TNT derivatives and smaller gaseous fragments prevails at higher compressions. At higher densities, enhanced carbon-clustering is observed, while the initial gaseous fragments formation is suppressed. Increasing the temperature speeds up the production of both clusters and gaseous products. The activation energy for the initial decomposition stage of ambient liquid TNT is ∼36 kcal/mol, close to the measured value (∼40 kcal/mol). This value is ∼25 kcal/mol lower than the corresponding gas phase C–N bond scission. Finally, we suggest a simple linear growth kinetic model for describing the clustering process, which provides very good agreement with simulation results.