where G monomer corresponds to the Gibbs free energy of the organic acid monomer, G water corresponds to the Gibbs free energy of a water molecule, G ions/salt corresponds to the Gibbs free energy of the Na + or Cl -ion or the NaCl pair, and n and m correspond to the number of water molecules and the number of ions in the cluster, respectively. We calculate the Gibbs free energy for each cluster component as a combination of a high-level electronic contribution and a DFT thermal free correction: