Ewald Summation Approach to Potential Models of Aqueous Electrolytes Involving Gaussian Charges and Induced Dipoles: Formal and Simulation Results

We present a detailed derivation of the complete set of expressions required for the implementation of an Ewald summation approach to handle the long-range electrostatic interactions of polar and ionic model systems involving Gaussian charges and induced dipole moments with a particular application to the isobaric-isothermal molecular dynamics (NPT-MD) simulation of our Gaussian charge polarizable (GCP) water model and its extension to aqueous electrolyte solutions. The set is comprised of the individual components of the potential energy, electrostatic potential, electrostatic field and gradient, electrostatic force, and corresponding virial. Moreover, we show how the derived expressions converge to known point-based electrostatic counterparts when the parameters, defining the Gaussian charge and induced dipole distributions, are extrapolated to their limiting point values. Finally, we test the simulation outcomes from the Ewald implementation against the corresponding reaction-field (RF) approach at three contrasting hydrogen-bonded water environments, including thermodynamic quantities, polarization behavior, and microstructural properties, where the simulated microstructures are compared with the available neutron scattering and X-ray diffraction data.