Automated Exploration of Chemical Reaction Pathways

Abstract

It has been a long standing problem to answer the following fundamental questions in chemistry; (1) what kinds of chemical compounds (isomers) can be produced from a set of atoms given by a chemical formula, such as H4C2O2, (2) how the isomers can be converted to one another, (3) how they are decomposed into smaller species, or conversely (4) how they are made of smaller species. Although this problem can be solved theoretically if all minima and pathways among them via saddles could be searched on the potential energy hypersurface, it has been believed to be impossible, when the number of atoms exceeds four in the target chemical formula. A very simple tool like a compass for voyage could be discovered for global reaction route mapping (GRRM) in the chemical world. That is the anharmonic downward distortion (ADD) which enables one to follow all reaction pathways from an equilibrium (EQ) point toward structures of transition states (TS) surrounding the EQ point. Subsequent downward followings from already found TSs can easily be made as conventional intrinsic reaction coordinate (IRC) followings to reach some EQ points and dissociation channels (DC). Further quests around newly found EQs will yield many more reaction pathways via many other TSs. Such one-after-another procedures will continue until no new EQ could be found, and finally one can obtain a global reaction route map of the chemical formula as well as the answers to the fundamental questions in chemistry. Now, one should step into the new era of chemical problems to perform a perfect microscopic control of chemistry involved in the stereo reaction dynamics of atoms and molecules, based on leading information on typical trajectories searched by the automated exploration of chemical reaction pathway