Evaluation of transition state properties by density functional theory

Durant, Joseph L.

doi:10.1016/0009-2614(96)00478-2

Cited by 289 publications

(239 citation statements)

References 27 publications

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“…This often improves the barriers but sometimes at the expense of the reaction energy. 42,43 As shown in Figure 1c, the TS optimized with BH&HLYP/6-31G-(d) is much earlier along the reaction path than the TS optimized with MP2(full)/6-31G(d) (R C-C ) 2.823 vs 2.538 Å, R C-Cl ) 1.893 vs 1.988 Å), and the barrier from the reactant complex 44,45 Bond additivity corrections (BACs) have been used to improve the calculation of thermochemistry. [46][47][48][49][50] Even though this is very efficient for getting more accurate reaction enthalpies, it appears not to have been used previously in molecular dynamics calculations.…”

Section: Resultsmentioning

confidence: 99%

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces

Shaik

Schlegel

2006

J. Phys. Chem. A

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The reaction of formaldehyde radical anion with methyl chloride, CH 2 O •-+ CH 3 Cl, is an example in which a single transition state leads to two products: substitution at carbon (Sub(C), CH 3 CH 2 O • + Cl -) and electron transfer (ET, CH 2 O + CH 3• + Cl -). The branching ratio for this reaction has been studied by ab initio molecular dynamics (AIMD). The energies of transition states and intermediates were computed at a variety of levels of theory and compared to accurate energetics calculated by the G3 and CBS-QB3 methods. A bond additivity correction has been constructed to improve the Hartree-Fock potential energy surface (BAC-UHF). A satisfactory balance between good energetics and affordable AIMD calculations can be achieved with BH&HLYP/6-31G(d) and BAC-UHF/6-31G(d) calculations. Approximately 200 ab initio classical trajectories were calculated for each level of theory with initial conditions sampled from a thermal distribution at 298 K at the transition state. Three types of trajectories were distinguished: trajectories that go directly to ET product, trajectories that go to Sub(C) product, and trajectories that initially go into the Sub(C) valley and then dissociate to ET products. The BH&HLYP/6-31G(d) calculations overestimate the number of nonreactive and direct ET trajectories because the transition state is too early. For the BH&HLYP and BAC-UHF methods, about one-third of the trajectories that initially go into the Sub(C) valley dissociate to ET products, compared to just over half with UHF/6-31G(d) in the earlier study. This difference can be attributed to a better value for the calculated energy release from the initial transition state and to an improved Sub(C) f ET barrier height with the BH&HLYP and BAC-UHF methods.

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Section: Resultsmentioning

confidence: 99%

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces

Shaik

Schlegel

2006

J. Phys. Chem. A

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“…It is generally known that for the DFT method, basis set convergence is fairly rapid compared with the MP2 method. However, the DFT method with the popular B3LYP functional [133] has difficulties in modeling transition-state structures and computation of activation energies [134,135]. In order to account for these difficulties, functionals such as BB1K [136], MPWB1K [137], and BMK [138] were developed for accurate computations of equilibrium parameters and activation energies of radical hydrogen abstraction and transfer reactions.…”

Section: Quantum Mechanical Methodsmentioning

confidence: 99%

Assessment of theoretical methods for the study of hydrogen abstraction kinetics of global warming gas species during their degradation and byproduct formation (IUPAC Technical Report)

Ramasami

Abdallah

Archibong

et al. 2013

Pure and Applied Chemistry

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Global climate change is a major concern as it leads to an increase in the average temperature of the earth's atmosphere. The existence and persistence of some gaseous species in the atmosphere contribute to global warming. Experimental techniques are used to study the kinetics and degradation of global warming gases. However, quantum mechanical methods are also useful for the kinetic and radiative forcing study of global warming species and can precede experimental investigations. Research has also been targeted to develop more adapted procedures using ab initio and density functional theory (DFT) methods. This report provides a global perspective, in simplified manner, of the theoretical studies of the degradation of gas species in the atmosphere with an emphasis on the hydrogen abstraction kinetics of global warming gas species during their degradation and byproduct formation. En route, the results obtained from these studies are analysed and compared with experimental data where available. Our analyses indicate that the theoretical predictions are in agreement with experimental findings but the predicted parameters are dependent on the method being used. Theoretical methods are used to predict the thermodynamic parameters of reactions, and, with relevance to this report, the global warming potential (GWP) index can also be calculated. This report can be useful for future investigations involving global warming gaseous species while providing suggestions on how computations can fill in data gaps when experimental data are unavailable.

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“…The energies of transition states predicted by this method, however, are often underestimated by about 5 kcal mol -1 [30,31]. This shortcoming lessens the accuracy of rate constants derived from the calculated energetics yet allows for an order-of-magnitude analysis.…”

Section: Energeticsmentioning

confidence: 99%

Graphene layer growth: Collision of migrating five-member rings

Whitesides

Kollias

Domin

et al. 2007

Proceedings of the Combustion Institute

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(not included in Total) 144Total 5787Accepted for Oral Presentation and Publication at st International Symposium on CombustionUniversity of Heidelberg, Germany, August 6-11, 20062 Abstract A reaction pathway is explored in which two cyclopenta groups combine on the zigzag edge of a graphene layer. The process is initiated by H addition to a five-membered ring, followed by opening of that ring and the formation of a six-membered ring adjacent to another fivemembered ring. The elementary steps of the migration pathway are analyzed using density functional theory to examine the region of the potential energy surface associated with the pathway. The calculations are performed on a substrate modeled by the zigzag edge of tetracene.Based on the obtained energetics, the dynamics of the system are analyzed by solving the energy transfer master equations. The results indicate energetic and reaction-rate similarity between the cyclopenta combination and migration reactions. Also examined in the present study are desorption rates of migrating cyclopenta rings which are found to be comparable to cyclopenta ring migration.

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Evaluation of transition state properties by density functional theory

Cited by 289 publications

References 27 publications

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces

Assessment of theoretical methods for the study of hydrogen abstraction kinetics of global warming gas species during their degradation and byproduct formation (IUPAC Technical Report)

Graphene layer growth: Collision of migrating five-member rings

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Evaluation of transition state properties by density functional theory

Cited by 289 publications

References 27 publications

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH2O•- + CH3Cl on Improved Potential Energy Surfaces

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH2O•- + CH3Cl on Improved Potential Energy Surfaces

Assessment of theoretical methods for the study of hydrogen abstraction kinetics of global warming gas species during their degradation and byproduct formation (IUPAC Technical Report)

Graphene layer growth: Collision of migrating five-member rings

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A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces

A Single Transition State Serves Two Mechanisms. The Branching Ratio for CH₂O^•- + CH₃Cl on Improved Potential Energy Surfaces