Charge Scaling Force Field for Biologically Relevant Ions Utilizing a Global Optimization Method

Charge scaling, also denoted as the electronic continuum correction, has proven to be an efficient method of effectively including electronic polarization in force field molecular dynamics simulations without additional computational costs. However, scaling charges in existing force fields, fitted at least in part to experimental data, leads to inconsistencies such as overscaling. We have, therefore, recently developed a 4-site water model consistent with charge scaling, i.e., possessing the correct low-frequency dielectric constant of 45. Here, we build on top of this water charge scaled models of biologically relevant Li+, Na+, K+, Ca2+, Mg2+ cations and Cl−, Br−, and I−, employing machine learning to streamline and speed-up the parameterization process. On the one hand, we show that the present model outperforms the best existing charge scaled model of aqueous ions. On the other hand, the present work points to a future need for improving consistently and simultaneously the water and ion models within the electronic continuum correction framework.