Towards large-scale, fully ab initio calculations of ionic liquids

Abstract

Ionic liquids have attracted a substantial amount of interest as replacement of traditional electrolytes in high efficiency electrochemical devices for generation and storage of energy due to their superior physical and chemical properties, especially low volatility and high electrochemical stability. For enhanced performance of the electrochemical devices ionic liquids are required to be highly conductive and low viscous. Long-range Coulomb and short-range dispersion interactions between ions affect physical and chemical properties of ionic liquids in a very complex way, thus preventing direct correlations to the chemical structure. Considering a vast combination of available cations and anions that can be used to synthesize ionic liquids, development of predictive theoretical approaches that allow for accurate tailoring of their physical properties has become crucial to further enhance the performance of electrochemical devices such as lithium batteries, fuel and solar cells. This perspective article gives a thorough overview of current theoretical approaches applied for studying thermodynamic (melting point and enthalpy of vapourisation) and transport (conductivity and viscosity) properties of ionic liquids, emphasizing their reliability and limitations. Strategies for improving predictive power and versatility of existing theoretical approaches are also outlined.

Simple and complex forms of disorder in ionic liquids

“…The consequence could be an inadequate appreciation of the relative positioning of two molecules, and subsequently of the energy and the entropy of the system. This type of misappreciation could lead to incorrect estimations of the micro-structure of these systems [50]. Polarization effects are less important with smaller molecules with smaller number of atoms, such as ethyl-ammonium nitrate (EAN) for example.…”

“…Polarization effects are less important with smaller molecules with smaller number of atoms, such as ethyl-ammonium nitrate (EAN) for example. The problem of the adequacy of simple force fields for complex RTILs have been recently posed [49,50]. In this context, modeling realistic RTILs appears to be a complex problem.…”

Theoretical reconstruction and elementwise analysis of photoelectron spectra for imidazolium-based ionic liquids

“…For the details of a dispersion correction for ionic liquids, see ref. 50 51 have identified in their quantum-chemical studies using ion pairs that the connection between cations and anions is predominantly established via the most acidic hydrogen bond to this ringcarbon and either the nitrogen or the oxygen of the [Tf 2 N] À anion. Within the large number of our ion pairs we have ascertained that the single point energy varies about DE = 171 meV.…”

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

“…Although quantum chemistry methods are very useful for characterizing the nature of the interactions in RTILs, [7][8][9][10] these techniques are limited to small gas phase systems and they are not yet appropriate for the sampling of liquid properties. Most of the literature therefore involves molecular dynamics (MD) simulations.…”