Fast-Tracking Transition-State Localization via Reaction Directional Analysis

Transition-state localization is critical for elucidating chemical reaction mechanisms but remains one of the most computationally demanding challenges in theoretical chemistry. Here, we introduce a novel method, reaction directional analysis-dimer (RDA-D), which integrates reaction directional analysis (RDA) with the dimer method to achieve efficient and reliable transition state searching. Reaction directional analysis generates high-quality quasi-transition-state structures directly from only the initial and final state geometries, combining dynamic interpolation, structural optimization, and directional analysis. These quasi-transition-state structures then serve as starting points for refinement via the dimer method. Benchmark tests on a diverse set of gas-phase and catalytic reactions on surfaces demonstrate that RDA-D is, on average, 5.83 times faster than the Nudged Elastic Band (NEB) method in CPU time and reduces the number of gradient evaluations by a factor of 4.74. Moreover, reaction directional analysis eliminates the need for predefined reaction coordinates or chemically intuitive initial guesses, providing a robust, scalable, and automation-friendly framework for transition-state localization.