SEM-Drude Model for the Accurate and Efficient Simulation of MgCl₂–KCl Mixtures in the Condensed Phase

Abstract

There is a long history of models that to different extents reproduce structural and dynamical properties of high-temperature molten salts. Whereas rigid ion models can work fairly well for some of the monovalent salts, polarizability is fundamentally important when small divalent or multivalent cations are combined with significantly polarizable anions such as Cl– to form networked liquids that display a first sharp diffraction peak. There are excellent polarizable ion models (PIMs) for these systems, but there has been little success with the less expensive Core–Shell type models, which are often described as unwieldy or difficult to fit. In this article, we present the Sharma–Emerson–Margulis (SEM)-Drude model for MgCl2/KCl mixtures that with the same ingredients used in the latest and most accurate PIM models overcome the aforementioned obstacles at significantly less computational cost; structural and dynamical properties are for all practical purposes very similar to what we obtain from the PIM but typical simulations can be more than 30 times faster. This has allowed us not only to expand our recent studies on the temperature and composition dependence of intermediate range order in MgCl2/KCl mixtures but also to access transport properties that were simply too costly to properly sample in our recently published studies.

Extension of the CL&Pol Polarizable Force Field to Electrolytes, Protic Ionic Liquids, and Deep Eutectic Solvents

“…The occurrence of these instabilities prompted us to also apply short-range damping (or smearing) to charge-induced dipole interactions. Our choice of shortrange damping functions was guided by the literature on polarizable simulations of molten salts, [39][40][41][42][43] where small monoatomic ions are common. The functional form of the Tang-Toennies damping functions, 38 originally devised for dispersion interactions, is kept,…”

“…For this purpose, we adapted the Tang-Toennies (TT) damping function, 38 which although developed originally for short-range damping of dispersion interactions, has been adapted for use in polarizable simulations of molten salts. [39][40][41][42][43] The main focus of the present work is the implementation and validation of specific short-range damping of strong charge-dipole interactions in order to ensure the stability of molecular dynamics trajectories in our problematic systems, and thus allowing the extension of the CL&Pol force field no important new classes of systems. Otherwise, we followed the strategy of our polarizable force field for ionic liquids, CL&Pol, which is a polarizable version of the widely-used CL&P fixed-charge force field for ionic liquids, [29][30][31] compatible with OPLS-AA 44 and therefore opening the possibility of simulating broad classes of molecular compounds, ions and materials.…”

Transferable, Polarizable Force Field for Electrolytes, Protic Ionic Liquids and Deep Eutectic Solvents

“…The occurrence of these instabilities prompted us to also apply short-range damping (or smearing) to charge-induced dipole interactions. Our choice of shortrange damping functions was guided by the literature on polarizable simulations of molten salts, [36][37][38][39][40] where small monoatomic ions are common. The functional form of the Tang-Toennies damping functions, 35 originally devised for dispersion interactions, is kept,…”

“…For this purpose, we adapted the Tang-Toennies (TT) damp-ing function, 35 which although developed originally for short-range damping of dispersion interactions, has been adapted for use in polarizable simulations of molten salts. [36][37][38][39][40] The main focus of the present work is the implementation and validation of specific short-range damping of strong charge-dipole interactions in order to ensure the stability of molecular dynamics trajectories in our problematic systems, and thus allowing the extension of the CL&Pol force field no important new classes of systems. Otherwise, we followed the strategy of our polarizable force field for ionic liquids, CL&Pol, which is a polarizable version of the widely-used CL&P fixed-charge force field for ionic liquids, 41,42 compatible with OPLS-AA 43 and therefore opening the possibility of simulating broad classes of molecular compounds, ions and materials.…”

Transferable, Polarizable Force Field for Electrolytes, Protic Ionic Liquids and Deep Eutectic Solvents

“…For this purpose, we adapted the Tang-Toennies (TT) damping function, 38 which although developed originally for short-range damping of dispersion interactions, has been adapted for use in polarizable simulations of molten salts. [39][40][41][42][43] The main focus of the present work is the implementation and validation of specific short-range damping of strong charge-dipole interactions in order to ensure the stability of molecular dynamics trajectories in our problematic systems, and thus allowing the extension of the CL&Pol force field no important new classes of systems. Otherwise, we followed the strategy of our polarizable force field for ionic liquids, CL&Pol, which is a polarizable version of the widely-used CL&P fixed-charge force field for ionic liquids, [29][30][31] compatible with OPLS-AA 44 and therefore opening the possibility of simulating broad classes of molecular compounds, ions and materials.…”