Fundamental Kinetic Modeling: ab initio rate constant calculations of elementary reactions

Abstract

Fundamental Kinetic Model' provides an alternative method for collecting rate constant data of elementary reactions when experimental observation is unavailable. A standard procedure of PMP4/6-3 IG*//UHF/6-3 IG* ab initio calculations of reactants and transition states provide the necessary information to calculate rate constants based upon conventional transition state theory and the Arrhenius equation. Unfortunately, this method yields erratic data. Ab initio energy calculations can vary drastically at different theory levels and basis sets. Even a small difference wi 'II result in large changes to the rate constant due to the exponential energy dependence of the Arrhenius equation. Therefore, a standardized theory level and basis set is currently unreasonable. Further, high level calculations require tremendous amounts of computer time, even when using the fastest available processors. Therefore, due to the time constraints of calculations and the ability to generate only approximate results at best, this method is recommended only when no other data is available.