MIT researchers developed a way to quickly calculate the transition state structure of a chemical reaction, using machine-learning models.
During a chemical reaction, molecules gain energy until they reach what's known as the transition state — a point of no return from which the reaction must proceed. This state is so fleeting that it's nearly impossible to observe it experimentally. The structures of these transition states can be calculated using techniques based on quantum chemistry, but that process is extremely time-consuming. A team of MIT researchers has now developed an alternative approach, based on machine learning, that can calculate these structures much more quickly — within a few seconds. Their new model could be used to help chemists design new reactions and catalysts to generate useful products like fuels or drugs, or to model naturally occurring chemical reactions such as those that might have helped to drive the evolution of life on Earth. "Knowing that transition state structure is really important as a starting point for thinking about designing catalysts or understanding how natural systems enact certain transformations," says Heather Kulik, an associate professor of chemistry and chemical engineering at MIT, and the senior author of the study. Chenru Duan PhD '22 is the lead author of a paper describing the work, which appears today in Nature Computational Science. Cornell University graduate student Yuanqi Du and MIT graduate student Haojun Jia are also authors of the paper. Fleeting transitions For any given chemical reaction to occur, it must go through a transition state, which takes place when it reaches the energy threshold needed for the reaction to proceed. The probability of any chemical reaction occurring is partly determined by how likely it is that the transition state will form. "The transition state helps to determine the likelihood of a chemical transformation happening. If we have a lot of something that we don't want, like carbon dioxide, and we'd like to convert it to a useful fuel like methanol, the transition state and how favorable that is determines…