Reactive Force Fields Based on Quantum Mechanics for Applications to Materials at Extreme Conditions

摘要: Understanding the response of energetic materials (EM) to thermal or shock loading at atomistic level demands a highly accurate description reaction dynamics multimillion-atom systems capture complex chemical and mechanical behavior involved: nonequilibrium energy/mass transfer, molecule excitation decomposition under high strain/heat rates, formation defects, plastic flow, phase transitions. To enable such simulations, we developed ReaxFF reactive force fields based on quantum mechanics (QM) calculations reactants, products, high-energy intermediates transition states, but using functional forms suitable for large-scale molecular simulations reactions extreme conditions. The elements are: - charge distributions change instantaneously as atomic coordinates change, all valence interactions use bond orders derived uniquely from distances which in turn describe energies forces, three body (angle) four (torsion inversion) terms are allowed not required, general "van der Waals" term describes short range Pauli repulsion long dispersion interactions, with Coulomb included between pairs atoms (no angle exclusions), no environmental distinctions made involving same element; thus every carbon has parameters whether diamond, graphite, benzene, porphyrin, allyl radical, HMX TATP. uses form hydrocarbons, polymers, metal oxides, alloys, allowing mixtures these into one simulation. We will present an overview recent progress developments, including extension nitramine-based (nitromethane, HMX) peroxide-based (TATP) explosives. demonstrate versatility transferability ReaxFF, also applications silicone polymer poly-dimethylsiloxane (PDMS).