Toward a quantitative theory of Hofmeister phenomena: From quantum effects to thermodynamics

Several recent developments have enhanced our understanding of specific ion hydration. These advances have included the Law of Matching Water Affinities and the realization that many-body dispersion forces and polarization can play important roles in ion specificity. Efforts have been made to partition the relevant ion free energies into their physically contributing parts in order to gain further insights into the driving forces. Yet a quantitative theory of ion specificity that links the necessary molecular-level treatment of the inner hydration shell with the many-body response of Lifshitz theory at longer range is still lacking. This review summarizes some steps toward quantitative models of specific ion hydration and discusses a possible path looking forward.