Predictive modeling of reaction equilibria presents one of the grand challenges in the field of molecular simulation. Difficulties in the study of such systems arise from the need (i) to accurately model both strong, short-ranged interactions leading to the formation of chemical bonds and weak interactions arising from the environment, and (ii) to sample the range of time scales involving frequent molecular collisions, slow diffusion, and infrequent reactive events. Here we present a novel reactive first principles Monte Carlo (RxFPMC) approach that allows for investigation of reaction equilibria without the need to pre-specify a set of chemical reactions and their ideal-gas equilibrium constants. RxFPMC simulations are used to predict speciation in (i) nitrogen/oxygen mixtures with varying composition at <i>T</i> = 3000 K and <i>p</i> = 30 GPa (i.e., conditions that are present in atmospheric lightning strikes and explosions), and in (ii) hydrogen sulfide/carbon dioxide mixtures in the vapor phase and adsorbed in all-silica and in cationic zeolites. The equilibrium distributions of compounds are compared to literature data, and structural information from the simulation trajectories is used to explain shifts in the equilibrium distributions caused by the environment.

Reactive first principles Monte Carlo simulations of nitrogen/oxygen and hydrogen sulfide/carbon dioxide mixtures

253rd National Meeting (2017)

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