Development of a Fluctuation-Assisted Molecular Dynamics Method for the Efficient Exploration of Chemical Reactions.

Fluctuation-assisted molecular dynamics (FMD) is developed as an enhanced sampling approach for efficiently exploring chemical reactions and generating reaction events within picosecond to subnanosecond time scales in quantum mechanical molecular dynamics (MD) simulations. In the FMD framework, the effective collision frequency among reactants is increased by restraining chemical species toward the center of fluctuation by using a harmonic potential with a time-dependent force constant, thereby promoting reactive encounters within a confined reaction space. The polymerization reactivity of a homogeneous acetylene system is investigated using FMD and compared with nanoreactor MD, a reaction discovery method based on high-temperature and high-pressure conditions induced by periodic compression and expansion of the simulation volume. Although both approaches exhibit comparable accelerations in reactant consumption and reaction event generation, the FMD method achieves this enhancement under significantly milder temperature and pressure conditions. These results demonstrate that FMD provides an efficient and physically moderate strategy for enhanced sampling of complex chemical reaction processes near equilibrium.