Insights Into the Uptake of N2O5 by Aqueous Aerosol Using Chemically Accurate Many-Body Potentials

Abstract

We study the uptake of N2O5 into pure water using molecular dynamics simulations performed with a recently developed, data driven MB-nrg model. Our model follows the same basis of the MB-pol water many body model and has coupled-cluster accuracy. We quantify the thermodynamics of solvation and adsorption using enhanced sampling techniques and free energy calculations. The free energy profile obtained highlights that N2O5 is selectively adsorbed to the liquid-vapor interface and weakly solvated. We further find that accommodation into the bulk solution occurs rather slowly, and competes with evaporation upon initial adsorption from the gas phase. The rates of each of these processes are evaluated using the free energy barriers and kinetically obtained fluxes. Leveraging the quantitative accuracy of the model, we parameterize and numerically solve a reaction-diffusion equation to determine a likely range of hydrolysis rates consistent with the experimentally observed reactive uptake coefficient in pure water. The physical and chemical parameters deduced here, including the solubility, accommodation coefficient, and hydrolysis rate, afford a foundation for which to consider the reactive loss of N2O5 in more complex solutions.