Richard Dawes of the Missouri University of Science and Technology is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry division to develop theoretical methods to study molecular dynamics and spectroscopy on multiple potential energy surfaces (PESs). Dawes and his research group are working to develop robust methods and software to construct accurate coupled multistate PESs. This involves systematic studies of systems which include various non-adiabatic interactions between states such as conical intersections, Renner-Teller, and spin-orbit coupling to assess the importance of such effects. The study compares cases where non-adiabatic effects provide an alternate mechanism (usually assumed to be a minor channel), with cases such as the reaction of triplet oxygen atoms with carbon monoxide to form carbon dioxide where the spin-forbidden channel is the only one available.
The potential energy surface (PES) is central to how chemists think about the structure and dynamics of molecular systems, in terms of minima and asymptotes connected by paths across landscapes or over energetic barriers. This project investigates systems for which subtle details of the PES topography and interactions between more than one of such surfaces have profound effects on reaction kinetics and on understanding and interpreting the dynamics. The project also focusses on making efficient use of many computer processors to solve the problem of generating accurate PESs for radicals and species with unusual bonding and electronic structures (particularly those of interest to atmospheric and interstellar chemistry). This will make the complete development of global PESs and subsequent quantum dynamics studies much more rapid and routine than is currently possible.
