Simulations of room temperature ionic liquids: from polarizable to coarse-grained force fields

Abstract

Room temperature ionic liquids (RTILs) are solvent with unusual properties, which are difficult to characterize experimentally because of their intrinsic complexity (large number of atoms, strong Coulomb interactions). Molecular simulations have therefore been essential in our understanding of these systems. Depending on the target property and on the necessity to account for fine details of the molecular structure of the ions, a large range of simulation techniques are available. Here I focus on classical molecular dynamics, in which the level of complexity of the simulation, and therefore the computational cost, mostly depends on the force field. Depending on the representation of the ions, these are either classified as all-atom or coarse-grained. In addition, all-atom force fields may account for polarization effects if necessary. The most widely used methods for RTILs are described together with their main achievements and limitations.

The properties of residual water molecules in ionic liquids: a comparison between direct and inverse Kirkwood–Buff approaches

“…2). It is known that standard atomistic force fields neglecting polarization effects quantitatively deviate from experimental findings related to the mean-square displacement of species 118,119 . However, here we are able to compare and discuss the results for the different species in a qualitative way.…”

Thermophysical properties of imidazolium tricyanomethanide ionic liquids: experiments and molecular simulation

“…by theoretical/molecular simulation methods [12][13][14][15][16][17][18][19][20] and several predictive models have been proposed. 11,[21][22][23][24] Currently it is well accepted that ILs are highly structured fluids in which the ion pairs arrange themselves into polar and non-polar domains.…”

Modelling Coupled Ion Motion in Electrolyte Solutions for Lithium‐Sulfur Batteries

“…Simply considering e = 1 in the Coulomb term would neglect the dynamic (induction) polarization effects, whereas including the static dielectric constant of the solvent would roughly amount to counting twice the static interactions. Recent theoretical works [46,47] have demonstrated that the electronic polarization in ionic liquids can be accounted for by scaling the Coulomb interactions by a factor 1-1/e el , where e el is the (fast/optical) electronic dielectric constant of the medium, which can be determined by experimental measures of the refractive index as e el = n 2 . [48] From the refractive indices of 1.3979 for DOL and 1.4307 for TEGDME at room temperature, [49] we obtain e el values of 1.18 for DOL and 1.19 for TEGDME.…”