A publication of the Advanced Simulation & Computing Division, NA-121.2, NNSA Defense Programs
June 2008
NA-ASC-500-08—Issue 7
Return to this issue’s stories
Explosives at the Microscopic Scale Produce Shocking Results
The first quantum molecular dynamics simulation of a shocked explosive near detonation conditions to reveal what happens at the microscopic scale was recently announced by researchers from Lawrence Livermore National Laboratory and the Massachusetts Institute of Technology. What they found was quite riveting: the explosive, nitromethane, undergoes a chemical decomposition and a transformation into a semi-metallic state for a limited distance behind the detonation front. “Despite the extensive production and use of explosives for more than a century, their basic microscopic properties during detonation haven’t been unraveled,” said lead author Evan Reed in a January 2008 article in Nature Physics. “We’ve gotten the first glimpse of the properties by performing the first quantum molecular dynamics simulation.”
Nitromethane is burned as a fuel in drag racers but can also be made to detonate, a special kind of burning in which the material undergoes a much faster and far more violent type of chemical transformation. With its single NO2 group, it is a simple, representative version of explosives with more NO2 groups. Though it is an optically transparent, electrically insulating material, it turns into an optically reflecting, nearly metallic state for a short time behind the detonation shock wave front. Behind the wave front, the material returns to being optically transparent and electrically insulating. “This is the first observation of this behavior in a molecular dynamics simulation of a shocked material,” Reed noted. “Ultimately, we may be able to create computer simulations of detonation properties of new, yet-to-be synthesized designer explosives.”
Other Livermore researchers include M. Riad Manaa, Laurence Fried, Kurt Glaesemann, and J.D. Joannopoulos of MIT.
Simulations show that molecules in detonating high explosives take on metallic properties. Metallic molecules are translucent, while insulating molecules are colored according to atom type: hydrogen is white, carbon is yellow, nitrogen is blue, and oxygen is red.
DOE Privacy Disclaimer | Sandia Privacy Disclaimer | 2008-4454 W
Developed and maintained by Sandia National Laboratories for NA-121.2