Detonation Pushes Limits Of Chemistry

The detonation of a nitrogen-based primary explosive occurs so quickly that it approaches the fundamental limits of chemistry, scientists report (Phys. Rev. Lett., DOI: 10.1103/physrevlett.109.038301). Detonations are difficult to study in the lab because the extreme sensitivity of these compounds carries a high risk of accidental explosions. Now, Evan J. Reed of Stanford University and colleagues have performed the first molecular dynamics simulation of a detonation of an azide, the primary explosive hydrazoic acid, which is sensitive to friction and heat. Previously, scientists have simulated the detonation of secondary explosives, which require a detonator to set them off. Such explosions occur on the order of a nanosecond. But the detonation of hydrazoic acid, from start to decomposition, occurs in only 10 picoseconds, which is on the order of vibrational timescales. “This reaction is likely one of the fastest naturally occurring chemical reactions,” write the researchers, and is surpassed only by ultrafast, photon-induced reactions. The researchers posit that this ultrafast chemistry may also be generalized to the detonation of other nitrogen-rich, high-energy-density materials such as N₄, N₅ ions, and polynitrogen.