The pre-optimization step should reduce the number of geometry cycles required to reach convergence at the B97-3c level, as the GFN1-xTB structures are still better than the output from the ABCluster force-field calculations. Figure presents the timings of the two approaches tested on 30 (SA) 10 (DMA) 10 cluster configurations. Geometry optimization done by GFN1-xTB only takes a few minutes. In contrast, B97-3c optimization takes between 10 and 25 hours. However, this pre-optimization significantly lowers the total run time of the DFT-3c methods by 30-50%. The pre-optimization did not significantly alter the final B97-3c geometries, as shown in the supporting information Figure . These findings show that while we cannot rely on the GFN1-xTB structures or energy for these large clusters, a massive amount of computational time is saved by using GFN1-xTB as a pre-optimization method. Figure also shows that r 2 SCAN-3c takes relatively more time to finish compared to B97-3c. Considering that r 2 SCAN-3c is also less accurate in calculating energies (see Figure ), B97-3c has been chosen for calculating the final results.