Early Stage Chemistry in Shock Compressed Carbon Monoxide: Development and Application of the ChIMES Model*

The formation of carbon condensates, or “soot” resulting from strong shockwave propagation in carbon-rich energetic materials can have significant implications on performance and sensitivity of energetic materials. The nucleation mechanism and distribution of these agglomerates is largely unknown, owing partially to associated time and length scales that are outside the accessible domain of standard quantum mechanics simulations, and to the lack of appropriate parameter sets for molecular mechanics based approaches. To this effect, we have developed ChIMES, a new reactive molecular dynamics force field that has been shown capable of retaining the accuracy of Kohn-Sham density functional theory while yielding orders of magnitude increases in computational efficiency and scalability. We use our ChIMES approach to study a model system of liquid CO under shock compression conditions, where current experiments are underway to study soot formation. Our results yield the possibility of a direct one-to-one comparison to these dynamic loading experiments, which could yield mechanistic and kinetic data with quantum accuracy.