MULTI-SCALE MOLECULAR DYNAMICS SIMULATION OF FUSED SILICA UNDER SHOCK IMPACT: PARAMETER CHARACTERIZATIONS

Silica is one of the most abundant substances on Earth. Chemically expressed as SiO2, silica exhibits a complicated phase diagram with multiple crystalline structures (polymorphs) at different temperature and pressure conditions. Under a shock impact, a significant amount of energy is effectively absorbed due to the phase transition of fused silica to stishovite, thereby taking most of the destructive energy away from these structures. Therefore, it is crucial to have a reliable method to investigate the mechanism behind the phase transition between fused silica and stishovite to better adapt this material as energy absorption and protection materials for future combat protection applications. In this work, the multi-scale shock technique (MSST) method is characterized to study the shock impact of fused silica. The BKS potential is employed to define the interatomic potential of fused silica. We calibrated two artificial MSST parameters, Q and tscale, concerning the simulation box size. We revealed the impact of cutoff radius rc on fused silica's phase transition under various shock velocity conditions. We found that the selection of rc in the BKS potential influences stishovite's nucleation, formation, and growth at different shock velocity conditions. Future work will expand the MSST method to eliminate the parameter calibration and better predict the material behavior under shock impact.