To illustrate our observations and the effect of D4S and D4SL, we will first discuss examples of small systems with nonphysical kinks, but no additional artificial minima in the potential energy surface caused by the D4 dispersion correction. Starting with the linear monocarbonyl potassium(I) complex [KCO] + , we calculated its potential energy along the K-C stretching coordinate with frozen C-O bondlength. The resulting potential energy curve is given in Figure . Since K + and CO are only weakly attracted, the PES of this system features a comparably shallow minimum. Its equilibrium bond distance is long (3.06 Å) and the K-C bond is highly deformable. Additionally, the pairwise C 6 coefficient between potassium and carbon differs drastically between uncoordinated potassium and monocoordinated potassium (Fig. ). The distance at which D4 perceives potassium to be coordinated by carbon is sufficiently close to the potential energy minimum in this system, wherefore the resulting jump in dispersion energy is seen in the shallow vicinity of the minimum energy geometry. In the case of BLYP-D4, the PES features an upwards bend at bond distances close to the minimum, which is shifted by approximately 0.3 Åwith respect to reference data. In the case of CAM-B3LYP-D4, the dispersion energy almost exactly counteracts the rise in DFT energy upon bond stretching from the minimum, resulting in a PES with an extremely flat minimum and a shifted minimum energy structure as well (3.11 Å). Additionally, the second derivative of the energy at equilibrium is significantly lower than the reference value, which affects the quality of harmonic vibrational energies and other quantities derived from locally harmonic approximations. It can be seen in Figure that both D4S and D4SL fix all of these issues and create a PES with energies sufficiently close to the reference.