We employed density functional theory-based ab initio molecular dynamics simulations to examine the hydration
structure of several common alkali and alkali earth metal cations. We found that the commonly used atom pairwise
dispersion correction scheme D3, which assigns dispersion coefficients based on the neutral form of the atom rather
than its actual oxidation state, leads to inaccuracies in the hydration structures of these cations. We evaluated this
effect for lithium, sodium, potassium, and calcium and found that the inaccuracies are particularly pronounced for
sodium and potassium compared to the experiment. To remedy this issue, we propose disabling the D3 correction
specifically for all cation-including pairs, which leads to a much better agreement with experimental data.