Ions interacting in solution: moving from intrinsic to collective properties

A crucial determinant of Hofmeister effects is the direct interaction of ions in solution with the charged groups on the surface of larger particles. Understanding ion-ion interactions in solution is therefore a necessary first step to explaining Hofmeister effects. Here, we advocate an approach to modeling these types of properties where state of the art Ab Initio Molecular Dynamics (AIMD) simulation of ions in solution is used to establish benchmark values for the intrinsic properties of ions in solution such as solvation structures and ion-ion Potentials of Mean Force (PMFs). This information can then be combined with, or used to parametrize and improve, reduced models, which use approximations such as the continuum solvent model (CSM). These reduced models can then be used to calculate collective and concentration dependent properties of electrolyte solution and so make accurate predictions about complex systems of relevance for direct applications. We provide an example of this approach using AIMD calculations of the sodium chloride PMF to calculate osmotic coefficients of all 20 alkali halide electrolytes