One should note that we have not in any way influenced the Z-matrix definitions. The procedure was completely black box, as a Z-matrix for the starting structure was automatically generated and the same construct was applied to the product state. If one does change the automatically determined references with the eyes of a human chemist, the results can be even improved. This is for example the case for reaction R6, where changing one reference atom in the Z-matrix brought the iteration number for internal coordinates down to 78 which is less than half of the 209 for IDPP (compare Figure ). Given that these IC-interpolations are already competitive with IDPP corrected pathways, one can expect that this performance can still be significantly improved.