Accurate calculations of reaction rates: predictive theory based on a rigorous quantum transition state concept

Manthe, Uwe

doi:10.1080/00268976.2011.564594

Cited by 52 publications

(50 citation statements)

References 138 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The eigenstates |f T of such a pair are complex conjugate of each other and can be interpreted as the ro-vibrational eigenstates of the activated complex. [51][52][53] For vanishing total angular momentum the number of non-zero eigenvalues of the thermal flux operator is small. 34 To finally obtain the CRP, these eigenstates are then propagated in real time.…”

Section: A Quantum Transition State Conceptmentioning

confidence: 99%

State-to-state reaction probabilities within the quantum transition state framework

Welsch

Huarte-Larrañaga

Manthe

2012

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

Rigorous quantum dynamics calculations of reaction rates and initial state-selected reaction probabilities of polyatomic reactions can be efficiently performed within the quantum transition state concept employing flux correlation functions and wave packet propagation utilizing the multi-configurational time-dependent Hartree approach. Here, analytical formulas and a numerical scheme extending this approach to the calculation of state-to-state reaction probabilities are presented. The formulas derived facilitate the use of three different dividing surfaces: two dividing surfaces located in the product and reactant asymptotic region facilitate full state resolution while a third dividing surface placed in the transition state region can be used to define an additional flux operator. The eigenstates of the corresponding thermal flux operator then correspond to vibrational states of the activated complex. Transforming these states to reactant and product coordinates and propagating them into the respective asymptotic region, the full scattering matrix can be obtained. To illustrate the new approach, test calculations study the D + H 2 (ν, j ) → HD(ν , j ) + H reaction for J = 0.

show abstract

Section: A Quantum Transition State Conceptmentioning

confidence: 99%

State-to-state reaction probabilities within the quantum transition state framework

Welsch

Huarte-Larrañaga

Manthe

2012

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Computational difficulties arise from the fact that harmonic transition state theory (TST) is often not a correct model due to strongly anharmonic hindered rotations and translations of the adsorbed molecules and a usually strong coupling of reactive and vibrational motion in the barrier region, 111 making more demanding dynamical sampling techniques necessary. However, such calculations are subject to serious convergence issues for systems as large as the ones studied in the present work.…”

Section: −68mentioning

confidence: 99%

Combined Density Functional Theory and Monte Carlo Analysis of Monomolecular Cracking of Light Alkanes Over H-ZSM-5

et al. 2012

View full text Add to dashboard Cite

Density functional calculations applying periodic boundary conditions have been performed to investigate adsorption and cracking of light alkanes (C 3 −C 6 ) on zeolite H-ZSM-5. Intrinsic energy barriers were obtained from singlepoint calculations by applying the revised form of the PBE functional (RPBE) to structures optimized on the PBE potential energy surface. Dispersion interactions were accounted for by adding a damped dispersion term to the PBE energies. The dependence of the adsorption enthalpy on the carbon number is in agreement with experimental observation. From intrinsic energy barriers, intrinsic rate coefficients were calculated by means of transition state theory. The dependence of the intrinsic enthalpy and entropy of activation on the carbon number is discussed and compared to experimental observations. Transition path sampling was employed to unravel qualitatively the reaction mechanism for cracking of butane. Monte Carlo simulations in the canonical ensemble were conducted to estimate the temperature dependence of the adsorption enthalpy and entropy of propane to nhexane. These quantities are not constant, as is often assumed in the interpretation of experimental data but become less negative with increasing temperature. It is shown how the selection of adsorption parameters influences the extraction of intrinsic rate parameters from experimental rate data. Based on the present analysis, an alternative partitioning of the experimentally accessible apparent entropy of activation into contributions from adsorption and intrinsic reaction is proposed.

show abstract

“…Nonetheless, the MCTDH results has remained as the most accurate quantum treatment and provide the benchmarks for all approximate models. 47 For the rate coefficients and kinetic isotope effects, it is not necessary to understand the complete reaction dynamics, as the state-to-state scattering attributes are averaged by the Boltzmann factor. Indeed, the transition-state theory (TST) offers a direct and more efficient theoretical approach for calculating rate coefficients.…”

Section: Introductionmentioning

confidence: 99%

Rate coefficients and kinetic isotope effects of the X + CH4 → CH3 + HX (X = H, D, Mu) reactions from ring polymer molecular dynamics

Suleimanov

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

The thermal rate coefficients and kinetic isotope effects have been calculated using ring polymer molecular dynamics (RPMD) for the prototypical reactions between methane and several hydrogen isotopes (H, D, and Mu). The excellent agreement with the theoretical rate coefficients of the H + CH 4 reaction obtained previously from a multiconfiguration time-dependent Hartree (MCTDH) calculation on the same potential energy surface provides strong evidence for the accuracy of the RPMD approach. These quantum mechanical rate coefficients are also in good agreement with the results obtained previously using the transition-state theory with semi-classical tunneling corrections for the H/D + CH 4 reaction reactions. However, it is shown that the RPMD rate coefficients for the ultralight Mu reaction with CH 4 are significantly smaller than the experimental data, presumably suggesting inaccuracies in the potential energy surface.Significant discrepancies between the RPMD and transition-state theory results have also been found for this challenging system.

show abstract

Accurate calculations of reaction rates: predictive theory based on a rigorous quantum transition state concept

Cited by 52 publications

References 138 publications

State-to-state reaction probabilities within the quantum transition state framework

State-to-state reaction probabilities within the quantum transition state framework

Combined Density Functional Theory and Monte Carlo Analysis of Monomolecular Cracking of Light Alkanes Over H-ZSM-5

Rate coefficients and kinetic isotope effects of the X + CH4 → CH3 + HX (X = H, D, Mu) reactions from ring polymer molecular dynamics

Contact Info

Product

Resources

About