Molecular Simulations of Aqueous Electrolytes: Role of Explicit Inclusion of Charge Transfer into Force Fields

Abstract

We describe here simulations of aqueous salt solutions that are performed using an explicit charge transfer force field. The emphasis of the discussion is on the calculation of a dynamical property of the solutions: selfdiffusion of water. While force fields that are based on pairwise additive potentials or on potentials with explicit inclusion of polarization or with scaled charges can provide at best a qualitative agreement with experiments, force fields with explicit inclusion of charge transfer can produce quantitative agreement with experiment for NaCl and KCl solutions. We argue that a force field with explicit charge transfer contains new physics absent in the previously used force fields described in recent reviews of molecular simulations of aqueous electrolytes.

On water reorientation dynamics in cation hydration shells

“…20 Classical forcefields were shown to lead to a retardation of water dynamics for all investigated cations, including Cs + , [19][20][21] which therefore contrasts with the acceleration that has been measured by several techniques for this dilute cation. This has led to the suggestion that DFT-based MD 21 or simulations accounting for charge transfer 22 are required. However, another promising approach relies on scaled ion charges, 23,24 that implicitly account for the fast electronic dielectric response of water.…”

“…We use molecular dynamics simulations which have already been successfully employed to elucidate how anions affect water reorientation dynamics. 7,8,14,15 However, for cations, traditional classical forcefields have been shown to fail to reproduce the experimentally observed acceleration of water dynamics induced by some large cations, [19][20][21] and it has been suggested that density functional theory(DFT)-based simulations 21 or simula-tions explicitly accounting for cation-water charge transfer 22 are required. Here we performed both DFT-based simulations and classical non-polarizable simulations with a rescaled-cation charge (ECC) approach.…”

Simulation of deep eutectic solvents: Progress to promises

“…126 Further reparameterization of polarizable FFs to improve agreement presents a major challenge as the slow dynamics of DESs necessitates in impractically long time lengths to achieve statistically accurate results. 124 New methods or approaches, perhaps encompassing machine learning or FFs with explicit inclusion of charge transfer, 149,150 will be required to achieve accurate self-diffusivity reproduction and prediction for DESs. As one considers the potential for dramatic computational advances over the next 25 years, it is not difficult to imagine a day when FFs could be completely replaced with low-cost QM methods, particularly for solvent systems such as DESs.…”

Simulating core electron binding energies of halogenated species adsorbed on ice surfaces and in solution via relativistic quantum embedding calculations

“…We note that considering the charged system without a counter ion implicitly assumes a model for a diluted solution/interface. From prior work with charged species in the literature such an approach is warranted if one takes into account the effects of the polarization of the solvent 86,[89][90][91][92][93][94] , and has been shown to yield spectroscopic results 62,95 that closely match experimental measurements, provided of course the model mirrors the essential features of the experimental system.…”