The PS region, similarly defined by the deviation from the optimised PS (dashed line in Fig. and) within ±0.1 Å, shows the largest energy prediction error along the IRC for both methods (Fig. ). However, these inaccuracies are not observed in the testing data generated from US/AIMD simulations. The contrasting MLIP performance on the two test sets arises from the different configurations generated by IRC and US/AIMD, where the former presents an idealised scenario, with the Cl-C-F bond angle remaining almost constant at 180°during the reaction, while during US/AIMD, it ranges from 150°to 180°illustrating the dynamic nature of the reactive processes (Fig. ).