Reaction pathways and rates from electronic structure theory

Two new saddle point search algorithms are presented. The first is a biased pseudo-Newton-Raphson algorithm that finds multiple reaction pathways by avoiding the region of known pathways. The second is an interpolating algorithm that grows the approximate minimum energy path inward from the reactant and product basins. This work also presents two corrections to transition state theory. The first correction is a reactive flux simulation using an ab initio reaction path Hamiltonian. An improved procedure for constructing the transverse eigensystem of the reaction path Hamiltonian was developed to facilitate the reactive flux simulations. The second correction uses the reaction path Hamiltonian in a non-separable semiclassical transition state theory to account for tunneling. The four new methods are tested on example problems. The new methods are used to test a hypothesized single-site mechanism for the oxidative carbonylation of methanol to dimethyl carbonate and side products on a copper-exchanged zeolite. A detailed analysis of side pathways shows that the hypothesized mechanism is incorrect and suggests an alternative mechanism.