title: Density-dependent liquid nitromethane decomposition: molecular dynamics simulations based on ReaxFF.
abstract: The decomposition mechanism of hot liquid nitromethane at various compressions was studied using reactive force field (ReaxFF) molecular dynamics simulations. A competition between two different initial thermal decomposition schemes is observed, depending on compression. At low densities, unimolecular C-N bond cleavage is the dominant route, producing CH(3) and NO(2) fragments. As density and pressure rise approaching the Chapman-Jouget detonation conditions (∼30% compression, >2500 K) the dominant mechanism switches to the formation of the CH(3)NO fragment via H-transfer and/or N-O bond rupture. The change in the decomposition mechanism of hot liquid NM leads to a different kinetic and energetic behavior, as well as products distribution. The calculated density dependence of the enthalpy change correlates with the change in initial decomposition reaction mechanism. It can be used as a convenient and useful global parameter for the detection of reaction dynamics. Atomic averaged local diffusion coefficients are shown to be sensitive to the reactions dynamics, and can be used to distinguish between time periods where chemical reactions occur and diffusion-dominated, nonreactive time periods.
authors.affiliation: Fritz Haber Research Center for Molecular Dynamics, Hebrew University, Jerusalem 91904, Israel.
authors.forename: Naomi
authors.initials: N
authors.lastname: Rom
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Zybin
authors.forename: Adri C T
authors.initials: AC
authors.lastname: van Duin
authors.forename: William A
authors.initials: WA
authors.lastname: Goddard
authors.forename: Yehuda
authors.initials: Y
authors.lastname: Zeiri
authors.forename: Gil
authors.initials: G
authors.lastname: Katz
authors.forename: Ronnie
authors.initials: R
authors.lastname: Kosloff
mesh_terms: D006358:Hot Temperature; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D009595:Nitroparaffins / Q000737:chemistry*
chemical_list: D009595:Nitroparaffins; D008697:Methane; C008640:nitromethane