A general small-curvature approximation for transition-state-theory transmission coefficients

Skodje, Rex T.; Truhlar, Donald G.; Garrett, Bruce C.

doi:10.1021/j150621a001

Cited by 371 publications

(288 citation statements)

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“…60,61 This method takes into account the corner cutting tendency of the tunneling for problems with a curved minimum energy path (MEP) near the TS. Since the recalculation of the MEP at many values of θ proved to be a laborious chore, we adopted the following streamlined procedure.…”

Section: Quantum Tunnelingmentioning

confidence: 99%

Theoretical Determination of the Rate Coefficient for the HO₂+ HO₂→ H₂O₂+O₂Reaction: Adiabatic Treatment of Anharmonic Torsional Effects

et al. 2012

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ABSTRACT:The HO 2 + HO 2 → H 2 O 2 + O 2 chemical reaction is studied using statistical rate theory in conjunction with high level ab initio electronic structure calculations. A new theoretical rate coefficient is generated that is appropriate for both high and low temperature regimes. The transition state region for the ground triplet potential energy surface is characterized using the CASPT2/CBS/aug-cc-pVTZ method with 14 active electrons and 10 active orbitals. The reaction is found to proceed through an intermediate complex bound by approximately 9.79 kcal/mol. There is no potential barrier in the entrance channel, although the free energy barrier was determined using a large Monte Carlo sampling of the HO 2 orientations. The inner (tight) transition state lies below the entrance threshold. It is found that this inner transition state exhibits two saddle points corresponding to torsional conformations of the complex. A unified treatment based on vibrational adiabatic theory is presented that permits the reaction to occur on an equal footing for any value of the torsional angle. The quantum tunneling is also reformulated based on this new approach. The rate coefficient obtained is in good agreement with low temperature experimental results but is significantly lower than the results of shock tube experiments for high temperatures.

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Section: Quantum Tunnelingmentioning

confidence: 99%

Theoretical Determination of the Rate Coefficient for the HO₂+ HO₂→ H₂O₂+O₂Reaction: Adiabatic Treatment of Anharmonic Torsional Effects

et al. 2012

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“…To estimate the reaction rates with tunneling effect included, we can use approximate methods, such as the semiclassical multidimensional tunneling model, [37][38][39][40][41] the approximate instanton theory, [42,43] and the ring-polymer molecular dynamics simulation. [44] In the present study, the canonical variational transition state theory (CVT) combined with the small-curvature tunneling (SCT) approximation [37][38][39] was used because this method has been applied to various small-sized to medium-sized reaction systems. [20,24,26,45] Brief explanation of the CVT and SCT is given in Appendix.…”

Section: Methodsmentioning

confidence: 99%

Reaction pathway and H/D kinetic isotope effects of the triple proton transfer in a 7‐hydroxyquinoline‐methanol complex in the ground state: A computational approach

Mori

2017

J of Physical Organic Chem

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Multiple proton transfer (PT) is an essential process in long-range proton transport such as proton relay in enzymes. 7-Hydroxyquinoline (7HQ) undergoes alcohol-mediated PT in both the excited and ground states, and this system has been investigated as a biomimetic model. In the present study, the reaction pathway of triple PT in a 7HQ-methanol cluster, 7HQ·(MeOH) 2 , in the ground state has been investigated using density functional theory calculations to clarify the reaction mechanism and the origin of the experimentally observed kinetic isotope effect (KIE). The PT takes place in an asynchronous concerted fashion, in which the oxygen atom in 7HQ first accepts a proton from the directly hydrogen-bonded MeOH. The rate constants and primary H/D KIEs have been estimated with canonical variational transition state theory in combination with the small curvature tunneling approximation. The tunneling effect on the PT rate is significant, and the KIE is much greater than 1 at room temperature. The rule of the geometric mean for the KIEs breaks down because of the asynchronicity in the motions of 3 protons and tunneling effect. In addition, the rate constant is smaller, the KIE is larger, and the activation energy is higher compared with the experimental values in heptane solution, suggesting that the PT dynamics in solution is governed by not only the intrinsic PT process but also thermal fluctuation of the solute and solvent molecules, which plays an important role in the configurational change of the 7HQ·(MeOH) 2 complex.

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“…More sophisticated and computationally demanding algorithms such as the ones developed by Truhlar [91][92][93][94][95][96][97] and Miller [98,99] should be used if more accurate results are necessary. In these methods, detailed knowledge of the reaction path is needed, making the computation of tunneling corrections of relatively large electronic structure systems such as the ones containing heavy halogenated atoms very time-consuming.…”

Section: Methodsmentioning

confidence: 99%

A Theoretical Study of the X-Abstraction Reactions (X = H, Br, or I) from CH₂IBr by OH Radicals: Implications for Atmospheric Chemistry

Šulka

Šulková

Louis

et al. 2013

Zeitschrift für Physikalische Chemie

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We report the calculation of the H-, Br-, and I-abstraction channels in the reaction of OH radicals with bromoiodomethane CH 2 IBr. The resulting energy profiles at 0 K were obtained by high-level all-electron ab initio methods including valence and core-valence electron correlation, scalar relativistic effects, spin-orbit coupling, spin-adaptation, vibration contributions, and tunneling corrections. In terms of activation enthalpy at 0 K, the energy profile for the Br-abstraction showed that this reaction pathway is not energetically favorable in contrast to the two other channels (H-and I-abstractions), which are competitive. The H-abstraction was strongly exothermic (−84.4 kJ mol −1 ), while the I-abstraction was modestly endothermic (16.5 kJ mol −1 ). On the basis of our calculations, we predicted the rate constants using canonical transition state theory over the temperature range 250-500 K for each abstraction pathway. The overall rate constant at 298 K was estimated to be 3.40 × 10 −14 and 4.22 × 10 −14 cm 3 molecule −1 s −1 for complex and direct abstraction mechanisms, respectively. In addition, the overall rate constant computed at 277 K was used in the estimation of the atmospheric lifetime for CH 2 IBr. On the basis of our theoretical calculations, the atmospheric lifetime for the OH removal process is predicted to be close to 1 year. In terms of atmospheric lifetime, the OH reaction is not competitive with the Cl reaction and photolysis processes.

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A general small-curvature approximation for transition-state-theory transmission coefficients

Cited by 371 publications

References 1 publication

Theoretical Determination of the Rate Coefficient for the HO₂+ HO₂→ H₂O₂+O₂Reaction: Adiabatic Treatment of Anharmonic Torsional Effects

Theoretical Determination of the Rate Coefficient for the HO₂+ HO₂→ H₂O₂+O₂Reaction: Adiabatic Treatment of Anharmonic Torsional Effects

Reaction pathway and H/D kinetic isotope effects of the triple proton transfer in a 7‐hydroxyquinoline‐methanol complex in the ground state: A computational approach

A Theoretical Study of the X-Abstraction Reactions (X = H, Br, or I) from CH₂IBr by OH Radicals: Implications for Atmospheric Chemistry

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A general small-curvature approximation for transition-state-theory transmission coefficients

Cited by 371 publications

References 1 publication

Theoretical Determination of the Rate Coefficient for the HO2 + HO2→ H2O2+O2Reaction: Adiabatic Treatment of Anharmonic Torsional Effects

Theoretical Determination of the Rate Coefficient for the HO2 + HO2→ H2O2+O2Reaction: Adiabatic Treatment of Anharmonic Torsional Effects

Reaction pathway and H/D kinetic isotope effects of the triple proton transfer in a 7‐hydroxyquinoline‐methanol complex in the ground state: A computational approach

A Theoretical Study of the X-Abstraction Reactions (X = H, Br, or I) from CH2IBr by OH Radicals: Implications for Atmospheric Chemistry

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Theoretical Determination of the Rate Coefficient for the HO₂+ HO₂→ H₂O₂+O₂Reaction: Adiabatic Treatment of Anharmonic Torsional Effects

Theoretical Determination of the Rate Coefficient for the HO₂+ HO₂→ H₂O₂+O₂Reaction: Adiabatic Treatment of Anharmonic Torsional Effects

A Theoretical Study of the X-Abstraction Reactions (X = H, Br, or I) from CH₂IBr by OH Radicals: Implications for Atmospheric Chemistry