Automated Generation of Reaction Complexes for Double-Ended Transition State Searches

Double-ended transition state (TS) search algorithms require reliable reactant and product geometries, which are often difficult to obtain. Here, we introduce Orienta, a lightweight tool that rapidly generates plausible reactant and product complexes by predicting atom connection orientations based on steric minimization principles inspired by VSEPR theory. Validation on a suite of 13 bimolecular reactions demonstrated that the generated complexes reliably support TS searches using NEB method. In addition, Orienta can generate adsorption and surface reaction orientations for clusters and periodic systems, showing excellent agreement with DFT-optimized structures. Despite certain limitationsincluding its inability to handle reactions that do not involve bond breaking or formation, such as intramolecular rotationsOrienta reduces the need for manual intervention and is capable of providing an effective front-end for fully automated double-ended TS searches. Orienta can be obtained at github.com/atomsos/orienta.