(731e) Molecular Modeling of Aqueous Electrolytes Based on the Gaussian Charge Polarizable Approach: Gaussian Charge-on-Spring Versus Dipole Self-Consistent Field Strategies to Induced Polarization
We present the derivation of the 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 simulation of our Gaussian Charge Polarizable (GCP) water model [2, 3] and its extension to aqueous electrolytes solutions. We also 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. Then, we developed the Gaussian charge-on-spring (GCOS) version  of the original self-consistent field (SCF) implementation of the GCP water model and test its accuracy to represent the polarization behavior of the original model involving smeared charges and induced dipole moments.
Finally, we test the simulation outcomes from the Ewald implementation against the corresponding reaction-field (RF) approach for the SCF implementation at three contrasting hydrogen-bonded water environments, including thermodynamic quantities, polarization behavior and microstructural properties, where the simulated microstructures are compared with the newest available neutron scattering and x-ray diffraction data. Moreover, we assessed the accuracy of the GCOS representation by a direct comparison of the resulting vapor-liquid phase envelope, microstructure, and relevant microscopic descriptors of water polarization along the orthobaric curve against the corresponding quantities from the corresponding SCF counterpart .
1. Chialvo, A.A. and L. Vlcek, Ewald Summation Approach to Potential Models of Aqueous Electrolytes Involving Gaussian Charges and Induced Dipoles: Formal and Simulation Results. The Journal of Physical Chemistry B, 2014. 118(47): p. 13658-13670.
2. Chialvo, A.A. and P.T. Cummings, Simple Transferable Intermolecular Potential for the Molecular Simulation of Water over Wide Ranges of State Conditions. Fluid Phase Equilibria, 1998. 150-151: p. 73-81.
3. Paricaud, P., et al., From dimer to condensed phases at extreme conditions: Accurate predictions of the properties of water by a Gaussian charge polarizable model. Journal Of Chemical Physics, 2005. 122(24).
4. Chialvo, A.A., et al., Vapor–Liquid Equilibrium and Polarization Behavior of the GCP Water Model: Gaussian Charge-on-Spring versus Dipole Self-Consistent Field Approaches to Induced Polarization. The Journal of Physical Chemistry B, 2015. 119(15): p. 5010-5019.