We recall that Li + and Mg 2+ have similar sizes of respectively σ Li + = 1.505 Å and σ Mg 2+ = 1.630 Å, as well as Cs + and Ba 2+ with a respective size of σ Cs + = 3.883 Å and σ Ba 2+ = 3.820 Å. A higher charge of the cation leads thus to a stronger energy of solvation. This observation is in qualitative agreement with previous experiments and simulations showing that only the first solvation shell is perturbed by monovalent cation, which is not the case for divalent cations where perturbations occur in the second solvation shell, that could account for the higher difference of chemical potential for divalent cation electrolytes. The evolution of the alchemical work for all alkali-chloride electrolyte solutions as a function of the NCMC moves is given in Figure and in the SI for every electrolytes (Figures