Reaction rate theories for

Wardlaw D M and Marcus R A 1984 RRKM reaction rate theory for transition states of any looseness Chem. Rhys. Lett. 110 230-4... 

Fortunately, the reaction rates of many important processes can be obtained without a full molecular dynamics simulation. Most reaction rate theories for elementary processes build upon the ideas introduced in the so-called transition state theory [88-90]. We shall focus on this theory here, particularly because it (and its harmonic approximation, HTST) has been shown to yield reliable results for elementary processes at surfaces. 

In electrochemical kinetics, there is a need to determine a similar quantity. However, there are eomplexities in the electrochemical case, because the reversible potential of the electrode reaction under examination varies with temperature.46 Thus, for a simple one-step electrode reaction, and substituting in the equation of the absolute reaction rate theory for the rate constant, k (cf. Eq. 4.112) ... 

The existence of bottlenecks to Hamiltonian transport suggests that intramolecular energy flow can be highly nonergodic. Thus, accounting for the bottlenecks should greatly improve chemical reaction rate theories. For example, for the 4 1 resonance shown in Figs. 2 and 3, the intramolecular bottleneck should be located at... 

In this chapter we have reviewed the development of unimolecular reaction rate theory for systems that exhibit deterministic chaos. Our attention is focused on a number of classical statistical theories developed in our group. These theories, applicable to two- or three-dimensional systems, have predicted reaction rate constants that are in good agreement with experimental data. We have also introduced some quantum and semiclassical approaches to unimolecular reaction rate theory and presented some interesting results on the quantum-classical difference in energy transport in classically chaotic systems. There exist numerous other studies that are not considered in this chapter but are of general interest to unimolecular reaction rate theory. 

A Kramers reaction rate theory for electrochemical ion transfer reactions. M. T. M. Koper and W. Schmickler, Chemical Physics 211, 123 (1996). 

Using absolute reaction rate theory for RSj and Rwsi2, Srinivas et al. come to ... 

Torney. D. C, and McConnell, H. M Diffusion-limited reaction rate theory for two-dimensional systems. Proc. R. Soc. London. Ser. A 387, 147 (1983). 

In summary, collision theory provides a good physical picture of bimolecular reactions, even though the structure of the molecules is not taken into account. Also, it is assumed that reaction takes place instantaneously in practice, the reaction itself requires a certain amount of time. The structure of the reaction complex must evolve, and this must be accounted for in a reaction rate theory. For some reactions, the rate coefficient actually decreases with increasing temperature, a phenomenon that collision theory does not describe. Finally, real molecules interact with each other over distances greater than the sum of their hard-sphere radii, and in many cases these interactions can be very important. For example, ions can react via long-range Coulomb forces at a rate that exceeds the collision limit. The next level of complexity is transition state theory. 

In order to obtain general expressions for various kinetic parameters such as the Tafel slope, it is necessary to take into account the stoichiometric correlation among the steps involved in the overall reaction. The stoichiometric number of the constituent step was thus introduced by Horiuti and employed in steady state reaction rate theory. " For the case where a unique rate-determining step (rds) exists in the reaction route, it directly follows from Eq. (12)... 

Klippenstein SJ, Marcus RA. (1989) Application of unimolecular reaction rate theory for highly flexible transition states to the dissociation of CH2CO into CH2 and CO. J. Chem. Phys. 91 2280-2292. 

Hill et al. [117] extended the lower end of the temperature range studied (383—503 K) to investigate, in detail, the kinetic characteristics of the acceleratory period, which did not accurately obey eqn. (9). Behaviour varied with sample preparation. For recrystallized material, most of the acceleratory period showed an exponential increase of reaction rate with time (E = 155 kJ mole-1). Values of E for reaction at an interface and for nucleation within the crystal were 130 and 210 kJ mole-1, respectively. It was concluded that potential nuclei are not randomly distributed but are separated by a characteristic minimum distance, related to the Burgers vector of the dislocations present. Below 423 K, nucleation within crystals is very slow compared with decomposition at surfaces. Rate measurements are discussed with reference to absolute reaction rate theory. 

The ratio kq/kf can now be identified as ki9/k9a. We can calculate an upper limit for kl9 from ion-molecule reaction rate theory by assuming that this reaction occurs with a collision efficiency. This leads to k9il < 1 X 109 sec. -1 (7). 

What is the aim of reaction rate theory Is the theory of practical use for scientists working in catalysis ... 

It is thus evident that the experimental results considered in sect. 4 above are fully consistent with the interpretation based on absolute reaction rate theory. Alternatively, consistency is equally well established with the quantum mechanical treatment of Buhks et al. [117] which will be considered in Sect. 6. This treatment considers the spin-state conversion in terms of a radiationless non-adiabatic multiphonon process. Both approaches imply that the predominant geometric changes associated with the spin-state conversion involve a radial compression of the metal-ligand bonds (for the HS -> LS transformation). 

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