Ab initio molecular dynamics simulations of nitromethane under shock initiation conditions
Detonation theories for homogeneous, condensed energetic materials have focused on 1-d analysis in which the detonation ignition physics forms the most difficult part. The classic ZND model considers detonation ignition through a frozen shock transition followed by an induction period, in which the shock temperature induces vibrational, rotational and electronic excitation followed by molecular dissociation (i.e., thermal decomposition). The frozen shock assumption has been the topic of debate and an alternative model has been proposed whereby detonation ignition arises from excitation of the translational degrees of freedom in the shock front . This raises an important postulation of detonation ignition of molecular condensed matter being initiated by non-equilibrium kinetic events within the shock front rather than equilibrium thermal molecular dissociation due to the shock temperature. Experimental support for this hypothesis must be derived from observations inside the shock front thereby requiring measurements on the time scale of 10−2−1 ps, which remains beyond the scope of current experimental techniques. However, the recent development of ab initio molecular dynamics simulations offers an alternative approach to elucidate possible mechanisms of detonation ignition. These methods are based on first-principle quantum mechanical calculations that allow for the simulation of chemical processes at the atomic level. Molecular dynamics simulations of bimolecular collisions using density functional theories serve as a most simplified model for shock-induced dissociation [2, 3], while multimolecular collisions including neighbourhood molecules serve as a simple model for shock dissociation in bulk liquid .
KeywordsShock Front Threshold Velocity Bond Scission Stationary Molecule Collision Velocity
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- 1.A.N. Dremin, V. Klimenko: ‘On the Effect of Shock Wave Front on the Reaction Origin’. In: Progress in Astronautics and Aeronautics 75. ed. by J.R. Bowen et al. (AIAA Inc., New York 1981) pp. 253–268Google Scholar
- 2.P.J. Haskins, M.D. Cook: ‘Shock-induced Reaction in Energetic Materials’. In: Shock Compression of Condensed Matter—1997. ed. by S.C. Schmidt et al. (AIP Press, New York 1998) pp. 305–308Google Scholar
- 3.D. Wei, F. Zhang, T.K. Woo: ‘Ab Initio Molecular Dynamics Simulations of Molecular Collisions of Nitromethane’. In: tShock Compression of Condensed Matter—2001. ed. by M.D. Furnish et al. (AIP, Melville, NY 2002) pp. 407–410Google Scholar
- 4.S.A. Decker, T.K. Woo, D. Wei, F. Zhang: ‘Ab Initio Molecular Dynamics Simulations of Multimolecular Collisions of Nitromethane and Compressed Liquid Nitromethane’. In: 12th International Symposium on Detonation 2002 Google Scholar