The investigation of the kinetics of reactions occurring over multiple well Potential Energy Surfaces (PES) is a time consuming and complicated task. In particular accounting properly for anharmonicities, variational effects, conformational analysis and high level estimation of energies for each well and transition state is of key relevance for the determination of accurate rate constants for each investigated reaction channel. Recently, we developed a code1, EStokTP, that can be used to determine automatically rate constants for single well reactions from a limited set of input files. In this presentation we will show how EStokTP can be used also to determine efficiently rate constant for reactions occurring over multiple wells, provided that the PES diagram is known. Two examples will be discussed: acetic acid decomposition and the reaction between O(3P) and butane. It will be shown how the incorporation of the calculated rate constants for acetic acid decomposition in a detailed kinetic mechanism allows to describe properly its combustion kinetics. The study of the reaction of O(3P) with butane, which involves intersystem crossing between the triplet and singlet PESs, is more complicated, as it requires to account properly for multireference effects. Complications and solutions devised to approach this system will be discussed together with a comparison between experimental results and theoretical calculations. Some considerations about the difficulty of determining rate laws for the O(3P) + alkene reaction family will finally be proposed.

Coupling automation of single well rate constant estimation with the investigation of multiple well potential energy surfaces

256th National Meeting (2018)

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