Development of Multistep Reaction Models with EOS for Energetic Materials

Energetic materials generally have complex structures which contain fuel and oxidizer in quite close contact such that chemical reaction and energy release can occur quite rapidly. Analyses of cook-off experiments by Tarver et al. (1996) showed that multistep kinetic processes can be resolved for them. Understanding these staged processes would be important for predicting the ignition and propagation of deflagration waves in various circumstances. Reactive molecular dynamics simulations can be used to characterize these reactions and intermediates, and work will be shown here for the analysis of HMX. By utilizing a combined Coordination Geometry Analysis and Non-negative Matrix Factorization (CGA-NMF) approach, cook-off simulations of these materials can be used to develop multistep kinetic schemes with Arrhenius type reaction models, including the Equations of State (EOS) for the intermediates. Such analytic models could then be directly implemented into mesoscale simulation codes. Larger scale MD simulations of deflagration waves in HMX were also performed and multistep lamellar deflagration waves are observed. The deflagration rates measured were consistent with experimental observations and were found to have a fair dependence on the temperature and pressure of the system.