Generalized transition state theory. Canonical variational calculations using the bond energy-bond order method for bimolecular reactions of combustion products

1979 ◽  
Vol 101 (18) ◽  
pp. 5207-5217 ◽  
Author(s):  
Bruce C. Garrett ◽  
Donald G. Truhlar
Keyword(s):  
Transition State ◽  
Bond Energy ◽  
Bond Order ◽  
Transition State Theory ◽  
Combustion Products ◽  
State Theory ◽  
Order Method ◽  
Bimolecular Reactions ◽  
Variational Calculations

Examination of Possible Non-Arrhenius Behavior in the reactions

1973 ◽  
Vol 51 (13) ◽  
pp. 2147-2154 ◽  
Author(s):  
Thomas C. Clark ◽  
John E. Dove
Keyword(s):  
Bond Energy ◽  
Classical Limit ◽  
Bond Order ◽  
Transition State Theory ◽  
Arrhenius Plot ◽  
State Theory ◽  
Rate Coefficients ◽  
Order Method ◽  
Arrhenius Behavior ◽  
Kinetic Measurements

We present a simplified form of the bond-energy–bond-order method of calculating rate coefficients which can be applied to reactions involving multi-atom reactants. Rate coefficients for the reactions[Formula: see text]are calculated for 300 < T < 1800°K. The Arrhenius plots of the calculated coefficients are curved, but in the temperature range 400–850°K where most kinetic measurements have been made the curvature is not large enough to be readily detected. However deviations from a linear Arrhenius plot should be observable if rate measurements are extended to higher temperatures by, e.g., shock tube experiments. The calculated rate coefficients at 300–1800°K are fitted by the expressions[Formula: see text]in liter mole second units. These expressions contain powers of T which in each case are greater than predicted by the classical limit of transition state theory. For all three reactions there is now some experimental evidence that the predicted curvature does occur. Some consequences of this behavior are examined.

Bimolecular Reactions, Transition-State Theory

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Transition State ◽  
Saddle Point ◽  
Transition State Theory ◽  
Classical Mechanics ◽  
Small Degree ◽  
State Theory ◽  
Reaction Coordinate ◽  
Partition Functions ◽  
Bimolecular Reactions ◽  
Activated Complex

This chapter discusses an approximate approach—transition-state theory—to the calculation of rate constants for bimolecular reactions. A reaction coordinate is identified from a normal-mode coordinate analysis of the activated complex, that is, the supermolecule on the saddle-point of the potential energy surface. Motion along this coordinate is treated by classical mechanics and recrossings of the saddle point from the product to the reactant side are neglected, leading to the result of conventional transition-state theory expressed in terms of relevant partition functions. Various alternative derivations are presented. Corrections that incorporate quantum mechanical tunnelling along the reaction coordinate are described. Tunnelling through an Eckart barrier is discussed and the approximate Wigner tunnelling correction factor is derived in the limit of a small degree of tunnelling. It concludes with applications of transition-state theory to, for example, the F + H2 reaction, and comparisons with results based on quasi-classical mechanics as well as exact quantum mechanics.

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