title: First-Principles Monte Carlo Simulations of Reaction Equilibria in Compressed Vapors.
abstract: 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 prespecify a set of chemical reactions and their ideal-gas equilibrium constants. We apply RxFPMC to investigate a nitrogen/oxygen mixture at T = 3000 K and p = 30 GPa, i.e., conditions that are present in atmospheric lightning strikes and explosions. The RxFPMC simulations show that the solvation environment leads to a significantly enhanced NO concentration that reaches a maximum when oxygen is present in slight excess. In addition, the RxFPMC simulations indicate the formation of NO2 and N2O in mole fractions approaching 1%, whereas N3 and O3 are not observed. The equilibrium distributions obtained from the RxFPMC simulations agree well with those from a thermochemical computer code parametrized to experimental data.
authors.affiliation: Department of Chemistry and Chemical Theory Center, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Evgenii O
authors.initials: EO
authors.lastname: Fetisov
authors.affiliation: Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory , Livermore, California 94550, United States.
authors.forename: I-Feng William
authors.initials: IF
authors.lastname: Kuo
authors.affiliation: Leadership Computing Facility, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Chris
authors.initials: C
authors.lastname: Knight
authors.affiliation: Department of Materials, ETH Zurich , Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland.
authors.forename: Joost
authors.initials: J
authors.lastname: VandeVondele
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Building 6-229, Cambridge, Massachusetts 02139-4307, United States.
authors.forename: Troy
authors.initials: T
authors.lastname: Van Voorhis
authors.affiliation: Department of Chemistry and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States; Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455-0132, United States.
authors.forename: J Ilja
authors.initials: JI
authors.lastname: Siepmann