The evolution of W 2H 2 O and its decomposition in the work performed during growth and charging as a function of NCMC moves is presented in Figure . It is clear that the variation of the non-bonded parameters between two alchemical segment is small enough to prevent blow-up of the system during the relaxation process by NVE MD as shown by the fluctuating but constant value of the work performed during growth (19.542 ± 0.184 kJ/mol) and charging (-68.309 ± 0.112 kJ/mol). Finally, one can deduced the free energy of solvation for electrolytes at infinite dilution, summarized in left column of Table . Overall, our calculations are in qualitative agreement with experimental results of Schmidt et al 41 in that the free energy are all negatives, and become less negative for larger ions. Also, Ross and Chodera calculated solvation free energy of NaCl at infinite dilution in TIP4P water and found -713.79 kJ/mol which are within 5% of our estimates (-733.4 KJ/mol). In addition, we estimated separately the variation of internal energy ∆U CnAm and deduced the variation of entropy ∆S CnAm from the variation of free solvation energy ∆F CnAm . The variation of free energy is the sum of the variation of internal energy and entropy