First-Principles Molecular Dynamics and Computed Rate Constants for the Series of OH-HX Reactions (X = H or the Halogens): Non-Arrhenius Kinetics, Stereodynamics and Quantum Tunnel

Coutinho, Nayara D.; Aquilanti, Vincenz̊o; Sanches-Neto, Flávio O.; Vaz, Eduardo C.; Carvalho-Silva, Valter H.

doi:10.1007/978-3-319-95174-4_47

Cited by 4 publications

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“…Situation is similar to the reaction of OH and H 2 , much studied experimentally and theoretically because of its simplicity: in a sense, it can be included in this series of OH + HX reaction when X = H. As expected, we have verified using present techniques together with path integral formulations that tunneling is the only mechanism for low temperature reactivity. In view of the so low number of electrons involved, we were able to observe that addition of water molecules enhances reactivity …”

Section: Additional Remarks and Conclusionmentioning

confidence: 99%

Kinetics of the OH+HCl→H₂O+Cl reaction: Rate determining roles of stereodynamics and roaming and of quantum tunneling

et al. 2018

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The OH + HCl → H2O + Cl reaction is one of the most studied four‐body systems, extensively investigated by both experimental and theoretical approaches. Here, as a continuation of our previous work on the OH + HBr and OH + HI reactions, which manifest an anti‐Arrhenius behavior that was explained by stereodynamic and roaming effects, we extend the strategy to understand the transition to the sub‐Arrhenius behavior occurring for the HCl case. As previously, we perform first‐principles on‐the‐fly Born–Oppenheimer molecular dynamics calculations, thermalized at four temperatures (50, 200, 350, and 500 K), but this time we also apply a high‐level transition‐state‐theory, modified to account for tunneling conditions. We find that the theoretical rate constants calculated with Bell tunneling corrections are in good agreement with extensive experimental data available for this reaction in the ample temperature range: (i) simulations show that the roles of molecular orientation in promoting this reaction and of roaming in finding the favorable path are minor than in the HBr and HI cases, and (ii) dominating is the effect of quantum mechanical penetration through the energy barrier along the reaction path on the potential energy surface. The discussion of these results provides clarification of the origin on different non‐Arrhenius mechanisms observed along this series of reactions. © 2018 Wiley Periodicals, Inc.

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Section: Additional Remarks and Conclusionmentioning

confidence: 99%

Kinetics of the OH+HCl→H₂O+Cl reaction: Rate determining roles of stereodynamics and roaming and of quantum tunneling

et al. 2018

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“…The first case has been treated amply elsewhere [59,63,64]; we mostly focused here on the second case [60,65]. Rarer cases are found for which d > 0 and ε ‡ < 0, and are referred as corresponding to an anti-Arrhenius behavior [66][67][68].…”

Section: Avoiding the Thermodynamic Limit Describes Nonlinearities Of Arrhenius Plotsmentioning

confidence: 99%

From the Kinetic Theory of Gases to the Kinetics of Rate Processes: On the Verge of the Thermodynamic and Kinetic Limits

2020

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A variety of current experiments and molecular dynamics computations are expanding our understanding of rate processes occurring in extreme environments, especially at low temperatures, where deviations from linearity of Arrhenius plots are revealed. The thermodynamic behavior of molecular systems is determined at a specific temperature within conditions on large volume and number of particles at a given density (the thermodynamic limit): on the other side, kinetic features are intuitively perceived as defined in a range between the extreme temperatures, which limit the existence of each specific phase. In this paper, extending the statistical mechanics approach due to Fowler and collaborators, ensembles and partition functions are defined to evaluate initial state averages and activation energies involved in the kinetics of rate processes. A key step is delayed access to the thermodynamic limit when conditions on a large volume and number of particles are not fulfilled: the involved mathematical analysis requires consideration of the role of the succession for the exponential function due to Euler, precursor to the Poisson and Boltzmann classical distributions, recently discussed. Arguments are presented to demonstrate that a universal feature emerges: Convex Arrhenius plots (super-Arrhenius behavior) as temperature decreases are amply documented in progressively wider contexts, such as viscosity and glass transitions, biological processes, enzymatic catalysis, plasma catalysis, geochemical fluidity, and chemical reactions involving collective phenomena. The treatment expands the classical Tolman’s theorem formulated quantally by Fowler and Guggenheim: the activation energy of processes is related to the averages of microscopic energies. We previously introduced the concept of “transitivity”, a function that compactly accounts for the development of heuristic formulas and suggests the search for universal behavior. The velocity distribution function far from the thermodynamic limit is illustrated; the fraction of molecules with energy in excess of a certain threshold for the description of the kinetics of low-temperature transitions and of non-equilibrium reaction rates is derived. Uniform extension beyond the classical case to include quantum tunneling (leading to the concavity of plots, sub-Arrhenius behavior) and to Fermi and Bose statistics has been considered elsewhere. A companion paper presents a computational code permitting applications to a variety of phenomena and provides further examples.

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The Increase of the Reactivity of Molecular Hydrogen with Hydroxyl Radical from the Gas Phase versus an Aqueous Environment: Quantum Chemistry and Transition State-Theory Calculations

Carvalho-Silva

Vaz

Coutinho

et al. 2019

Computational Science and Its Applications – ICCSA 2019

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First-Principles Molecular Dynamics and Computed Rate Constants for the Series of OH-HX Reactions (X = H or the Halogens): Non-Arrhenius Kinetics, Stereodynamics and Quantum Tunnel

Cited by 4 publications

References 79 publications

Kinetics of the OH+HCl→H₂O+Cl reaction: Rate determining roles of stereodynamics and roaming and of quantum tunneling

Kinetics of the OH+HCl→H₂O+Cl reaction: Rate determining roles of stereodynamics and roaming and of quantum tunneling

From the Kinetic Theory of Gases to the Kinetics of Rate Processes: On the Verge of the Thermodynamic and Kinetic Limits

The Increase of the Reactivity of Molecular Hydrogen with Hydroxyl Radical from the Gas Phase versus an Aqueous Environment: Quantum Chemistry and Transition State-Theory Calculations

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First-Principles Molecular Dynamics and Computed Rate Constants for the Series of OH-HX Reactions (X = H or the Halogens): Non-Arrhenius Kinetics, Stereodynamics and Quantum Tunnel

Cited by 4 publications

References 79 publications

Kinetics of the OH+HCl→H2O+Cl reaction: Rate determining roles of stereodynamics and roaming and of quantum tunneling

Kinetics of the OH+HCl→H2O+Cl reaction: Rate determining roles of stereodynamics and roaming and of quantum tunneling

From the Kinetic Theory of Gases to the Kinetics of Rate Processes: On the Verge of the Thermodynamic and Kinetic Limits

The Increase of the Reactivity of Molecular Hydrogen with Hydroxyl Radical from the Gas Phase versus an Aqueous Environment: Quantum Chemistry and Transition State-Theory Calculations

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Kinetics of the OH+HCl→H₂O+Cl reaction: Rate determining roles of stereodynamics and roaming and of quantum tunneling

Kinetics of the OH+HCl→H₂O+Cl reaction: Rate determining roles of stereodynamics and roaming and of quantum tunneling