Ultrafast detonation of hydrazoic acid: a case study of the ChIMES model

Understanding the chemical evolution and states of matter of an energetic material under detonation is challenging due to the short time scales of chemical reactions and risk of experimental work. First-principle molecular dynamics simulations can provide valuable insights into such systems. However, the computational cost associated with those simulations limits their applicability to relatively small systems and short time scales. We have developed the Chebyshev Interaction Model for Efficient Simulation (ChIMES), a reactive force field, using force matching to trajectories from density functional theory (DFT). This force field has been shown to be capable of retaining the accuracy of DFT simulation while increasing orders of magnitude in computational efficiency. In this work, we use ChIMES to study hydrazoic acid, an azide energetic material that exhibits an ultrafast detonation during a shock wave. We find that our models are able to accurately reproduce the structural and dynamic properties computed from DFT at different thermodynamic states. The ability to describe charge transfer and chemical reactions is also discussed.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.