[SY-N3] Accelerated quantum molecular dynamics simulations of chemistry under extreme conditions
Atomistic simulations are a key component to understand reaction chemistry in materials; for instance, the detonation chemistry of energetic materials under pressure, which is characterized by rapid breaking and remaking of covalent bonding, and where intermediate products and reaction rates are difficult to characterize in experiments.
While accurate methods exist to study systems of relevant size with explicit electronic contributions critical to the description of bonds, e.g. density functional tight-binding (DFTB), the timescale of the simulation is often limited to a few hundreds of picoseconds. This restrains the study to systems in which reactions occur relatively quickly. In the case of detonation chemistry, this implies high pressure and temperature. In order to consider less extreme conditions, one can benefit from the rare occurrence of chemical reactions to use accelerated molecular dynamics methods such as parallel replica dynamics (PRD).
In this work, we describe efforts to combine the DFTB code LATTE, developed at LANL, with the PRD method, in order to perform accelerated QMD (AQMD) simulations of reactive chemistry. AQMD was first applied to the study of liquid benzene, a prototypical reactive hydrocarbon that has been studied both experimentally and theoretically. AQMD allowed to perform simulations reaching several nanoseconds, and thus the observation of reactions at pressures below 20 GPa. Importantly, these simulations unraveled the precursor reaction to polymerization: the formation of Diels-Alder dimers.
While accurate methods exist to study systems of relevant size with explicit electronic contributions critical to the description of bonds, e.g. density functional tight-binding (DFTB), the timescale of the simulation is often limited to a few hundreds of picoseconds. This restrains the study to systems in which reactions occur relatively quickly. In the case of detonation chemistry, this implies high pressure and temperature. In order to consider less extreme conditions, one can benefit from the rare occurrence of chemical reactions to use accelerated molecular dynamics methods such as parallel replica dynamics (PRD).
In this work, we describe efforts to combine the DFTB code LATTE, developed at LANL, with the PRD method, in order to perform accelerated QMD (AQMD) simulations of reactive chemistry. AQMD was first applied to the study of liquid benzene, a prototypical reactive hydrocarbon that has been studied both experimentally and theoretically. AQMD allowed to perform simulations reaching several nanoseconds, and thus the observation of reactions at pressures below 20 GPa. Importantly, these simulations unraveled the precursor reaction to polymerization: the formation of Diels-Alder dimers.