XLI.—Studies in catalysis. Part IX. The calculation in absolute measure of velocity constants and equilibrium constants in gaseous systems

Lewis, William C.

doi:10.1039/ct9181300471

Cited by 71 publications

(27 citation statements)

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“…Chemistry is known to be at the boundary of both the applicability of classical models and the necessity of quantum mechanical concepts. On the one side, theories that are at least partially based on assumptions from classical mechanics like transition-state theory (TST) [1,2] and classical collision theory [3,4] can accurately predict reaction rates in certain parameter regimes, but on the other side are usually insufficient to give a general description of chemical reactions, particularly when quantum-nuclear effects such as zero-point energy, quantum tunneling [5] or nonadiabaticity [6] play an important role [7][8][9][10]. For the case of TST, it was realized early by Wigner that it is not possible to reintroduce these quantum effects in a simple way after making the classical assumption along the reaction coordinate [8], because all degrees of freedom are coupled together [9,10].…”

Section: Introductionmentioning

confidence: 99%

Exploring the effects of quantum decoherence on the excited-state dynamics of molecular systems

2021

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Fewest-switches surface hopping (FSSH) is employed in order to investigate the nonadiabatic excited-state dynamics of thiophene and related compounds and hence to establish a connection between the electronic system, the critical points in configuration space and the deactivation dynamics. The potential-energy surfaces of the studied molecules were calculated with complete active space self-consistent field and time-dependent density-functional theory. They are analyzed thoroughly to locate and optimize minimum-energy conical intersections, which are essential to the dynamics of the system. The influence of decoherence on the dynamics is examined by employing different decoherence schemes. We find that irrespective of the employed decoherence algorithm, the population dynamics of thiophene give results which are sound with the expectations grounded on the analysis of the potential-energy surface. A more detailed look at single trajectories as well as on the excited-state lifetimes, however, reveals a substantial dependence on how decoherence is accounted for. In order to connect these findings, we describe how ensemble averaging cures some of the overcoherence problems of uncorrected FSSH. Eventually, we identify carbon–sulfur bond cleavage as a common feature accompanying electronic transitions between different states in the simulations of all thiophene-related compounds studied in this work, which is of interest due to their relevance in organic photovoltaics.

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Section: Introductionmentioning

confidence: 99%

Exploring the effects of quantum decoherence on the excited-state dynamics of molecular systems

2021

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“…For instance, (1~ for all one-dimensional type I cases (e.g., A+A~0 and A+A~A), rate = -dp/dt = kp 3 (5) which is equivalent asymptotically to rate = K(t) p2 (6) where K(t) is given by Eq. (1), i.e., K(t)=kot 1/2~p(t) (7) because in one dimension S~ t 1/2 and from Eqs. (5) and (6) it follows that p ~ t 1/2.…”

Section: Introductionmentioning

confidence: 99%

Space-and time-resolved diffusion-limited binary reaction kinetics in capillaries: experimental observation of segregation, anomalous exponents, and depletion zone

1991

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An experimental investigation of one-dimensional, diffusion-limited A + B ~ C chemical reactions is reported. The persistence of reactant segregation and the formation of a depletion zone is observed and expressed in terms of the universal time exponents: c~ (motion of the boundary zone), fl (width of instantaneous product formation zone), 7 (rate of instantaneous local formation of product), c~ (rate of instantaneous global formation of product), etc. There is good agreement with the recently predicted and/or simulated values: ~= 1/2, fl= 1/6, 7=2/3, 6=1/2, in contrast to classical predictions (c~=0, r 1/2, ~=0, =-1/2). Furthermore, classically the segregation would not be preserved and there would be no formation of a depletion zone and no motion (just dissipation) of the reaction zone. We also discuss the relations to electrode oxidation-reduction reactions, i.e.

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“…In gas-phase theory, collision theory was developed in 1916 by Trautz and in 1918 by Lewis [32,36,37] and allows interpreting the kinetic law and its parameters. Subsequently, developing TST allowed Laidler and Glasstone (from 1935) to apply these concepts to a large diversity of reactions [25,38], such as:…”

Section: The Formulation Of the Arrhenius Formmentioning

confidence: 99%

Origin and Justification of the Use of the Arrhenius Relation to Represent the Reaction Rate of the Thermal Decomposition of a Solid

et al. 2021

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Degradation models are commonly used to describe the generation of combustible gases when predicting fire behavior. A model may include many sub-models, such as heat and mass transfer models, pyrolysis models or mechanical models. The pyrolysis sub-models require the definition of a decomposition mechanism and the associated reaction rates. Arrhenius-type equations are commonly used to quantify the reaction rates. Arrhenius-type equations allow the representation of chemical decomposition as a function of temperature. This representation of the reaction rate originated from the study of gas-phase reactions, but it has been extrapolated to liquid and solid decomposition. Its extension to solid degradation needs to be justified because using an Arrhenius-type formulation implies important simplifications that are potentially questionable. This study describes these simplifications and their potential consequences when it comes to the quantification of solid-phase reaction rates. Furthermore, a critical analysis of the existing thermal degradation models is presented to evaluate the implications of using an Arrhenius-type equation to quantify mass-loss rates and gaseous fuel production for fire predictions.

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XLI.—Studies in catalysis. Part IX. The calculation in absolute measure of velocity constants and equilibrium constants in gaseous systems

Abstract: View Article Online * This is the most direct means of obtaining the critical increment. the spectrum of the substance provided the data are available.

Cited by 71 publications

References 0 publications

Exploring the effects of quantum decoherence on the excited-state dynamics of molecular systems

Exploring the effects of quantum decoherence on the excited-state dynamics of molecular systems

Space-and time-resolved diffusion-limited binary reaction kinetics in capillaries: experimental observation of segregation, anomalous exponents, and depletion zone

Origin and Justification of the Use of the Arrhenius Relation to Represent the Reaction Rate of the Thermal Decomposition of a Solid

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