Monte Carlo Transition State Search (MCTSS) Program Applied in Theoretical Studies of Criegee intermediates reactions

Criegee intermediates (CI) are key intermediates in the reaction of ozone with alkenes. The stabilized Criegee intermediates (sCI) can react with atmospheric species such as water vapor, NO2, SO2, oxygenates etc. The oxidation of these substances by stabilized Criegee intermediates in ozonolysis of alkenes can influence the formation of secondary organic aerosol (SOA) and new particle. Criegee intermediate has a very short lifetime and CI reactions are extremely complicated. It's hard to have a clear understanding of various reaction channels simply from experimental or modeling approaches, and generally requires theoretical explanation or predication. Theoretical studies of Criegee intermediates mechanism and kinetics are among the central topics in the atmospheric aerosol sciences. Recently, we have developed an effective program named Monte Carlo Transition State Search (MCTSS) program with ab initio optimization for finding saddle points of atmospheric reaction systems. The program can connect with Gaussian, NWChem and DMol3 seamlessly. We plan to exploit the advances our group has made in finding the transition state structures automatically and effectively. To elucidate the reaction mechanism and kinetics of CI reactions, computational quantum chemistry and theoretical kinetic methodologies are needed by calculations utilizing NWChem and Polyrate. The proposed tasks include continued research in the following general areas: (1) Development of MCTSS program; (2) Criegee intermediates reactions.