Direct ab initio dynamics methods for calculating thermal rates of polyatomic reactions

We present a direct ab initio dynamics methodology for calculating thermal rate constants from density functional theory (DFT). Dynamical theory is based on a variational transition state theory plus multi-dimensional semi-classical tunneling approximations. Potential energy surface information is calculated from a combined DFT/ab initio Molecular Orbital theory approach. We also present applications of this method to predicting detailed dynamics of a hydrogen abstraction reaction and proton transfer in a model biological system to illustrate its versility, accuracy and prospects for molecular modeling of reactive dynamics of polyatomic chemical reactions.