After identifying that the problem likely lies within the D3 model, we decided to perform a twodimensional scan along the problematic normal modes. To isolate the problem specifically to the H2 movement, we conducted a restricted scan where the cluster was frozen (using the H2-NiKur-(2) geometry), while the H2 coordinates were varied. We selected two degrees of freedom to vary: the H-H distance and the distance between Ni and the center of mass of the H2 molecule. For the latter degree of freedom, the coordinates of the H2 atoms were shifted along the plane created by the Ni and the two H atoms. The results of the scan are shown in Figure , bottom. To our surprise, we found two local minima on the PES. Notably, one of the minima (corresponding to H2-NiKur-( )) had an unnaturally high curvature along the Ni-H2 distance degree of freedom, resulting in an extremely high frequency for the translational mode of the H2 molecule. Although the barrier between the two local minima is not very high (~5 kJ/mol), it was sufficient to cause our initial geometry optimization to be trapped in this ill-behaved local minimum. Additionally, this type of PES can significantly affect the results of some dynamical methods, such as AIMD, by providing incorrect distributions in the phase space.