Once the reaction has completed and the path found, the maximum energy structure along the path is extracted along with the two neighbouring structures. A linear interpolation (10 points from maximum energy structure to both neighbours) is performed and the interpolated structures are subjected to single point energy calculations using both Density Functional Theory (DFT) and GFN2-xTB. All DFT calculations are performed with the Gaussian 16 program . The maximum GFN2-xTB energy along the interpolated path is used to estimate the GFN2-xTB barrier (orange part of the flow chart, Figure ). The maximum energy structure based on DFT calculations is used as initial guess for the TS structure in a DFT TS search [opt=(calcall, ts, noeigen)]. Whether the correct TS is found is evaluated based on an intrinsic reaction coordinate (IRC) path search in both forward and reverse direction from the found TS. From the endpoint structures of the IRC, the adjacency matrices are extracted. The adjacency matrix for an N atom system is an N × N matrix with 1 on the off-diagonal elements linking atoms that are bonded and 0 if the atoms are not bonded. The structures are converted from coordinates to adjacency matrix using xyz2mol. The assignment of bond/no bond is done using the xyz2mol program based on a simple extended Hückel theory (EHT) calculation and the Mulliken overlap population between each pair of atoms as implemented in RDKit . The adjacency matrices for the endpoints of the IRC are compared with the adjacency matrices for the intended reactant and product structures to determine if a TS for the intended reaction is found. If the adjacency matrices of the IRC endpoint structures do not match those of the input reactant and product structures it may be due to the IRC not haven completed as the IRC calculations often crash before converging to reactant/product structures. Thus, the endpoints of the IRC are geometry optimized, and these structures checked by the same procedure. If either sets of structures (based on adjacency matrices) match the input structures, the TS for the given reaction is concluded to have been found and the search procedure terminated.