Properties of the polarizable MARTINI water model: A comparative study for aqueous electrolyte solutions

The coarse-grained MARTINI approach is nowadays used for the simulation of charged systems. A robust and valid water model to reproduce electrostatic screening effects in addition to hydration properties is therefore of crucial importance. We study the properties of the polarizable MARTINI water model in the presence of varying sodium chloride concentrations to test the validity of the approach. The numerical findings are compared to results that are obtained by a Kirkwood-Buff based atomistic force field in combination with the SPC/E water model. An acceptable agreement between both approaches and experimental results is observed for dynamic properties like ionic conductivities, diffusion coefficients and the dielectric constants when a rescaling approach is used. Slighter deviations can be observed for the mass density as well as for the local surrounding of the ions which can be related to the spherical geometry of the polarizable MARTINI water beads. We highlight agreements and differences and discuss the corresponding consequences.