in the Supporting Information) and the number of water molecules in the first solvation shell around ions (Tables ). The hydration shells around ions are disturbed when concentration of electrolyte increases, which lower solvation energy of salt ions. Another common trend highlighted is that the alchemical work and chemical potential increases in absolute value when the radius of the ion diminishes, because smaller ions have a higher solvation free energy. The absolute difference of chemical potential after insertion of an electrolyte unit is about ∼ 215 kJ/mol between LiCl and CsCl, and about ∼ 494 kJ/mol between MgCl 2 and BaCl 2 , which is more than twice the value for monovalent electrolytes.