Chapter 5 Constructing Reaction Mechanisms

Abstract

Publisher Summary This chapter focuses on the development of detailed mechanisms of elementary chemical reactions. The reaction mechanisms have evolved over several decades with the support of extensive experimental measurements of species thermochemistry and the kinetics of elementary reactions. Increasingly powerful computational tools for predicting reaction thermochemistry and kinetics, along with the still-growing database of experimental results, have shortened the time required to develop relatively complete mechanisms of elementary reactions to describe some new overall vapor-phase transformations. The reaction mechanism consists of a list of elementary reactions occurring in the system under conditions of interest, along with rate parameters for those reactions and thermochemical properties of all the chemical species participating in the reactions. To illustrate this methodology, some representative examples are considered, including the thermal decomposition of the chlorosilanes and the thermal decomposition of aluminum chloride. The construction of detailed mechanisms of elementary reactions is only a tractable problem in the gas phase, where reactions occur among isolated molecules, and, with more difficulty, at gas–solid interfaces. The chapter also focuses on identifying reactions, determining species thermochemistry, determining rate parameters, applying the reaction mechanism, and validating and refining the mechanism based on sensitivity analysis, rate or flux analysis, and comparison with any available experiments.