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Example: chain-branching reaction O+H2 -> OH+H

Reaction O+H2->OH+H is one of chain-branching reactions in the practically important process of hydrogen combustion. The rate constant of this reaction was evaluated using the transition state theory. This theory is applicable if only one potential barrier occurs in the reaction path from the reagents to the products and there are no deep potential wells (see left figure). The height of the potential barrier between the reagents and products and the parameters characterizing the structure of the transition complex (rotational constants, vibrational frequencies) were taken from the work [T.J.Truhlar, D.G.Truhlar, B.C.Garret, J. Chem. Phys., 88, 6983 (1988)], in which they were calculated by quantum-chemical mehods.

The results of Kintech Lab calculations are presented in the right figure along with the available experimental data. It can be seen that the transition state theory with the parameters obtained from quantum chemical calculations provides the quantitative description of the direct bimolecular reaction.

Rate constant k of the reaction O+H2->OH+H
Reaction energy path profile of the direct bimolecular reaction X+Y->Z+W.
Rate constant k of the reaction O+H2->OH+H. The results of calculations are shown by the blue line; the experimental data (J.B.Sutherland, J.V.Michael, and A.N.Pirraglia et al Twenty-first Symposium on Combustion. The Combustion Institute, Pittsburg, 1988, p.929) are shown by the red line.

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