Large-scale Molecular Simulations of Hypervelocity Impact of Materials

Abstract

We describe the application of the ReaxFF reactive force field with short-range distance-dependent exponential inner wall corrections and the non-adiabatic electron Force Field (eFF) for studying the hypervelocity impact (HVI) effects on material properties. In particular, to understanding nonequilibrium energy/mass transfer, high strain/heat rate material decomposition, defects formation, plastic flow, phase transitions, and electronic excitation effects that arise from HVI impact of soft and hard materials on different material surfaces. Novel results are presented on the single shock Hugoniot and shock chemistry of Nylon6-6, on the hypervelocity shock sensitivity of energetic materials with planar interfacial defects and on HVI chemistry of silicon carbide surfaces with diamondoid nanoparticles. Both methods provide a means to elucidate the chemical, atomic and molecular processes that occur within the bulk and at the surfaces of materials subjected to HVI conditions and constitute a critical tool to enabling technologies required for the next generation of energy, spatial, transportation, medical, and military systems and devices, among many others. This has proven to be extremely challenging, if not impossible, for experimental observations, mainly because the material states that occur are hard to isolate and their time scales for changes are too rapid (<1 ps). First principles quantum mechanics (QM) simulation methods have also been bounded by the prohibitive scaling cost of propagating the total Schrödinger equation for more than 100 atoms at finite temperatures and pressures.

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