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Bimolecular Reaction

The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform

David E Manolopoulos – 1st expert on this subject based on the ideXlab platform

  • Resonances in Bimolecular Reactions
    PhysChemComm, 2020
    Co-Authors: Rex T. Skodje, David E Manolopoulos

    Abstract:

    In this Perspective we briefly review our recent studies which prove unequivocally the existence of a quantum dynamical resonance in the F + HD → HF + D Reaction. The signatures of the resonance in the integral and differential cross sections of this Reaction are elucidated. The interplay between experiment and theory is crucial in establishing the existence of a resonance in a Bimolecular Reaction and in revealing its physical characteristics.

  • Bimolecular Reaction rates from ring polymer molecular dynamics application to h ch4 h2 ch3
    Journal of Chemical Physics, 2011
    Co-Authors: Yury V Suleimanov, Rosana Collepardoguevara, David E Manolopoulos

    Abstract:

    In a recent paper, we have developed an efficient implementation of the ring polymer molecular dynamics (RPMD) method for calculating Bimolecular chemical Reaction rates in the gas phase, and illustrated it with applications to some benchmark atom‐diatom Reactions. In this paper, we show that the same methodology can readily be used to treat more complex polyatomic Reactions in their full dimensionality, such as the hydrogen abstraction Reaction from methane, H + CH4 → H2 + CH3. The present calculations were carried out using a modified and recalibrated version of the Jordan‐ Gilbert potential energy surface. The thermal rate coefficients obtained between 200 and 2000 K are presented and compared with previous results for the same potential energy surface. Throughout the temperature range that is available for comparison, the RPMD approximation gives better agreement with accurate quantum mechanical (multiconfigurational time-dependent Hartree) calculations than do either the centroid density version of quantum transition state theory (QTST) or the quantum instanton (QI) model. The RPMD rate coefficients are within a factor of 2 of the exact quantum mechanical rate coefficients at temperatures in the deep tunneling regime. These results indicate that our previous assessment of the accuracy of the RPMD approximation for atom‐diatom Reactions remains valid for more complex polyatomic Reactions. They also suggest that the sensitivity of the QTST and QI rate coefficients to the choice of the transition state dividing surface becomes more of an issue as the dimensionality of the Reaction increases. © 2011 American Institute of Physics. [doi:10.1063/1.3533275]

  • Bimolecular Reaction rates from ring polymer molecular dynamics
    Journal of Chemical Physics, 2009
    Co-Authors: Rosana Collepardoguevara, Yury V Suleimanov, David E Manolopoulos

    Abstract:

    We describe an efficient procedure for calculating the rates of Bimolecular chemical Reactions in the gas phase within the ring polymer molecular dynamics approximation. A key feature of the procedure is that it does not require that one calculate the absolute quantum mechanical partition function of the reactants or the transition state: The rate coefficient only depends on the ratio of these two partition functions which can be obtained from a thermodynamic integration along a suitable Reaction coordinate. The procedure is illustrated with applications to the three-dimensional H+H2, Cl+HCl, and F+H2 Reactions, for which well-converged quantum reactive scattering results are computed for comparison. The ring polymer rate coefficients agree with these exact results at high temperatures and are within a factor of 3 of the exact results at temperatures in the deep quantum tunneling regime, where the classical rate coefficients are too small by several orders of magnitude. This is probably already good enoug…

Rosana Collepardoguevara – 2nd expert on this subject based on the ideXlab platform

  • Bimolecular Reaction rates from ring polymer molecular dynamics application to h ch4 h2 ch3
    Journal of Chemical Physics, 2011
    Co-Authors: Yury V Suleimanov, Rosana Collepardoguevara, David E Manolopoulos

    Abstract:

    In a recent paper, we have developed an efficient implementation of the ring polymer molecular dynamics (RPMD) method for calculating Bimolecular chemical Reaction rates in the gas phase, and illustrated it with applications to some benchmark atom‐diatom Reactions. In this paper, we show that the same methodology can readily be used to treat more complex polyatomic Reactions in their full dimensionality, such as the hydrogen abstraction Reaction from methane, H + CH4 → H2 + CH3. The present calculations were carried out using a modified and recalibrated version of the Jordan‐ Gilbert potential energy surface. The thermal rate coefficients obtained between 200 and 2000 K are presented and compared with previous results for the same potential energy surface. Throughout the temperature range that is available for comparison, the RPMD approximation gives better agreement with accurate quantum mechanical (multiconfigurational time-dependent Hartree) calculations than do either the centroid density version of quantum transition state theory (QTST) or the quantum instanton (QI) model. The RPMD rate coefficients are within a factor of 2 of the exact quantum mechanical rate coefficients at temperatures in the deep tunneling regime. These results indicate that our previous assessment of the accuracy of the RPMD approximation for atom‐diatom Reactions remains valid for more complex polyatomic Reactions. They also suggest that the sensitivity of the QTST and QI rate coefficients to the choice of the transition state dividing surface becomes more of an issue as the dimensionality of the Reaction increases. © 2011 American Institute of Physics. [doi:10.1063/1.3533275]

  • Bimolecular Reaction rates from ring polymer molecular dynamics
    Journal of Chemical Physics, 2009
    Co-Authors: Rosana Collepardoguevara, Yury V Suleimanov, David E Manolopoulos

    Abstract:

    We describe an efficient procedure for calculating the rates of Bimolecular chemical Reactions in the gas phase within the ring polymer molecular dynamics approximation. A key feature of the procedure is that it does not require that one calculate the absolute quantum mechanical partition function of the reactants or the transition state: The rate coefficient only depends on the ratio of these two partition functions which can be obtained from a thermodynamic integration along a suitable Reaction coordinate. The procedure is illustrated with applications to the three-dimensional H+H2, Cl+HCl, and F+H2 Reactions, for which well-converged quantum reactive scattering results are computed for comparison. The ring polymer rate coefficients agree with these exact results at high temperatures and are within a factor of 3 of the exact results at temperatures in the deep quantum tunneling regime, where the classical rate coefficients are too small by several orders of magnitude. This is probably already good enoug…

Angelo Valleriani – 3rd expert on this subject based on the ideXlab platform

  • single molecule stochastic times in a reversible Bimolecular Reaction
    Journal of Chemical Physics, 2012
    Co-Authors: Peter E Keller, Angelo Valleriani

    Abstract:

    In this work, we consider the reversible Reaction between reactants of species A and B to form the product C. We consider this Reaction as a prototype of many pseudobiomolecular Reactions in biology, such as for instance molecular motors. We derive the exact probability density for the stochastic waiting time that a molecule of species A needs until the Reaction with a molecule of species B takes place. We perform this computation taking fully into account the stochastic fluctuations in the number of molecules of species B. We show that at low numbers of participating molecules, the exact probability density differs from the exponential density derived by assuming the law of mass action. Finally, we discuss the condition of detailed balance in the exact stochastic and in the approximate treatment.