Microscopic rate coefficients in reactions with flexible transition states: Analysis of the transitional-mode sum of states

Smith, Sean C.

doi:10.1063/1.460846

Cited by 36 publications

(14 citation statements)

References 55 publications

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“…3. W1 and RSEs are generally close to experimental values, CBS-RAD and G3(MP2)-RAD produce good BDEs 64.…”

supporting

confidence: 68%

Advances in modeling hydrocarbon cracking kinetic predictions by quantum chemical theory: A review

Shi

2018

Int J Energy Res

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Summary In the modeling of hydrocarbon thermal cracking processes, complicated reaction networks of multicomponent reactants make kinetic parameter predictions very challenging. To solve this problem, the additivity method and Evans‐Polanyi equation were proposed for the prediction of kinetic factors. As the calculation of kinetic parameters using quantum chemical theory was used for higher accuracy, new additivity methods at the quantum theory level were developed for the prediction of thermodynamic kinetic parameters. At the same time, a reaction class transition state theory RC‐TST, analogous to the Evans‐Polanyi equation, was proposed by considering quantum factors for kinetic constant evaluation. Quantum calculation methods promoted mechanistic studies of electronic effects to accurately reveal the kinetic constant rules with different structural factors. Under these circumstances, kinetic parameter predictions by different quantum chemical computation methods were firstly introduced and reviewed. Meanwhile, development of the new additivity method and RC‐TST theory at the quantum chemistry level were summarized, and the new outlook on electronic effects with an appropriate quantum chemical computational method into the new additivity method was conducted to develop more perspicuous and accuracy in a simplified method for the calculation of complicated thermal cracking reaction.

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“…3. W1 and RSEs are generally close to experimental values, CBS-RAD and G3(MP2)-RAD produce good BDEs 64.…”

supporting

confidence: 68%

Advances in modeling hydrocarbon cracking kinetic predictions by quantum chemical theory: A review

Shi

2018

Int J Energy Res

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“…An important feature of the PSI-VTST approach is its classically accurate treatment of the interfragment couplings, low-frequency-mode anharmonicities, and low-frequency-mode vibration−rotation couplings while conserving J . Recent advances in the methodology, involving analytic integrations over the momentum portions of the phase space integrals, have yielded algorithms of sufficient efficiency to be widely applicable. ,− Furthermore, simplified expressions providing extremely efficient approximate estimates have also been presented . Unfortunately, the implicit assumption of a center-of-mass separation distance reaction coordinate breaks down at shorter separation distances, particularly for those reactions where at least one of the atoms involved in the reactive bond is well separated from the fragment center of mass…”

Section: Reactions Without An Intrinsic Potential Barriermentioning

confidence: 99%

Current Status of Transition-State Theory

1996

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We present an overview of the current status of transition-state theory and its generalizations. We emphasize (i) recent improvements in available methodology for calculations on complex systems, including the interface with electronic structure theory, (ii) progress in the theory and application of transition-state theory to condensed-phase reactions, and (iii) insight into the relation of transition-state theory to accurate quantum dynamics and tests of its accuracy via comparisons with both experimental and other theoretical dynamical approximations.

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“…Phase space variables for a triatomic molecule are the Euler angular momenta (P θ , P ϕ , P χ ), their conjugate 58,59 coordinates (θ, ϕ, χ), the vibrational normal coordinates, (Q 1 , Q 2 , Q 3 ), and their conjugate momenta (P 1 , P 2 , P 3 ). The dimensionless phase space volume-element, dΓ 12 , is dQ 1 dQ 2 dQ 3 dθ dϕ dχ dP 1 dP 2 dP 3 dP θ dP ϕ dP χ /h 6 .…”

Section: K Rec Based On K-active Rrkm Theorymentioning

confidence: 99%

Bimolecular Recombination Reactions: K-Adiabatic and K-Active Forms of RRKM Theory, Nonstatistical Aspects, Low-Pressure Rates, and Time-Dependent Survival Probabilities with Application to Ozone. 2

Ghaderi

Marcus

2014

J. Phys. Chem. A

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We consider for bimolecular recombination reactions the K-adiabatic versus the K-active forms of RRKM theory, where K is the component of the total angular momentum along the axis of least moment of inertia of the recombination product. When that product is approximately a prolate symmetric top, with two moments of inertia of the product substantially larger than the third, K becomes a dynamically slowly varying quantity and the K-adiabatic form of RRKM theory is the appropriate version to use. Using classical trajectory results for the rate constant for ozone formation in the low-pressure region as an example, excellent agreement for the recombination rate constant k rec with the K-adiabatic RRKM theory is observed. Use of a two transition state (inner, outer TS) formalism also obviates any need for assessing recrossings in the exit channel. In contrast, the K-active form of RRKM theory for this system disagrees with the trajectory results by a factor of about 2.5. In this study we also consider the distribution of the (E, J) resolved time-dependent survival probabilities P(E, J, t) of the intermediate O 3 * formed from O + O 2 . It is calculated using classical trajectories. The initial conditions for classical trajectories were selected using action-angle variables and a total J representation for (E, J) resolved systems, as described in Part I. 1 The difference between K-active and K-adiabatic treatments is reflected also in a difference of the K-active RRKM survival probability P(E, J, t) from its trajectory-based value and from its often non-single-exponential decay. It is shown analytically that k rec (K-active) ≥ k rec (K-adiabatic), independent of the details of the TS (e.g., variational or fixed RRKM theory, 1-TS or 2-TS). Nonstatistical effects for O 3 * formation include a small initial recrossing of the transition state, a slow (several picoseconds) equipartitioning of energy among the two O−O bonds of the newly formed O 3 *, and a small nondissociation (a quasi-periodicity) of some trajectories originating in O 3 * (∼10%) and so, by microscopic reversibility, are not accessible from O + O 2 . An apparently new feature of the present results is the comparison of classical trajectories with K-adiabatic and K-active theories for rate constants of bimolecular recombinations. The quantum mechanical counterpart of classical K-adiabatic RRKM theory is also given, and its comparison with the experimental k rec for O 3 is given elsewhere.

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Microscopic rate coefficients in reactions with flexible transition states: Analysis of the transitional-mode sum of states

Cited by 36 publications

References 55 publications

Advances in modeling hydrocarbon cracking kinetic predictions by quantum chemical theory: A review

Advances in modeling hydrocarbon cracking kinetic predictions by quantum chemical theory: A review

Current Status of Transition-State Theory

Bimolecular Recombination Reactions: K-Adiabatic and K-Active Forms of RRKM Theory, Nonstatistical Aspects, Low-Pressure Rates, and Time-Dependent Survival Probabilities with Application to Ozone. 2

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