(716a) Mesoscale Modeling of Energy Release Processes: Dissipative Particle Dynamics Simulations of Shear Initiated Behavior

Brennan, J. K., U.S. Army Research Laboratory
Lisal, M., Academy of Sciences of the Czech Republic
Bonet Avalos, J., Universitat Rovira i Virgili

Mechanically-stimulated phenomena such as shock or shear of energetic materials can occur over a wide range of spatial and temporal scales. For example, localized regions of elevated thermal energy, or hot spots, can occur in the material due to shock heating. Typically in energetic materials, these hot spots occur near microscale defects in the material such as voids and grain boundaries but the energy transfer processes can be atomistically governed. While modeling and simulation of such phenomena can offer fundamental insight, it is computationally challenging. Computing power and resources continue to grow, but there still exists much behavior that cannot be studied using molecular simulation techniques. Moreover, field-based mesoscale modeling techniques have fidelity limitations with respect to gaining a fundamental understanding.

In this study, particle-based mesoscale modeling is used to help characterize energy release processes that occur when an energetic material is sheared. Effects on the energy transfer are characterized by considering several factors, including, the shear rate and the orientation of grain boundaries relative to the shear. We implement the energy-conserving version of the Dissipative Particle Dynamics method (DPDE) [1-4]. In contrast to the standard Dissipative Particle Dynamics method, the DPDE method simulates the hydrodynamic behavior of materials while conserving both momentum and energy. The DPDE method assigns an internal energy to each particle which allows particles to exchange both momentum and thermal energy. This particle energy is included as a separate equation of motion along with the equations of motion for the particle's position and momentum. The atomic degrees of freedom which are explicitly resolved into the mesoparticle internal energy account for the atomic vibrations in an averaged way. We demonstrate that the DPDE method is a viable tool for simulating energy release processes of energetic crystalline materials.

1Bonet Avalos, J., and A.D. Mackie, Europhysics Letters, 40, 141 (1997).

2Español, P., Europhysics Letters, 40, 631 (1997).

3Mackie, A.D., J. Bonet Avalos, and V. Navas, Phys. Chem. Chem. Phys., 1, 2039 (1999).

4Bonet Avalos, J., and A.D. Mackie, J. Chem. Phys., 111, 5267 (1999).