Computationally Efficient Prediction of Ionic Liquid Properties (original) (raw)
2014, The Journal of Physical Chemistry Letters
Due to fundamental differences, room-temperature ionic liquids (RTIL) are significantly more viscous than conventional molecular liquids and require long simulation times. At the same time, RTILs remain in the liquid state over a much broader temperature range than the ordinary liquids. We exploit the ability of RTILs to stay liquid at several hundred degrees Celsius and introduce a straightforward and computationally efficient method for predicting RTIL properties at ambient temperature. RTILs do not alter phase behavior at 600−800 K. Therefore, their properties can be smoothly extrapolated down to ambient temperatures. We numerically prove the validity of the proposed concept for density and ionic diffusion of four different RTILs. This simple method enhances the computational efficiency of the existing simulation approaches as applied to RTILs by more than an order of magnitude. SECTION: Liquids; Chemical and Dynamical Processes in Solution
Related papers
Understanding Ionic Liquids through Atomistic and Coarse-Grained Molecular Dynamics Simulations
Accounts of Chemical Research, 2007
Understanding the physical properties of ionic liquids (ILs) via computer simulation is important for their potential technological applications. The goal of our IL research is to obtain a unified understanding of the properties of ILs with respect to their underlying molecular structure. From atomistic molecular dynamics simulations, the many-body electronic polarization effect was found to be important for modeling ILs, especially their dynamics. The multiscale coarse-graining methodology has also been employed to increase the simulation speed by a factor of 100 or more, thereby making it possible to study the mesoscopic behavior of ILs by computer simulations. With these simulation techniques, ILs with an amphiphilic cation were found to exhibit a spatial heterogeneity due to the aggregation of their nonpolar alkyl tails. This spatial heterogeneity is a key feature in interpreting many physical phenomena of ILs, such as their heterogeneous selfdiffusion and surface layering, as well as their surfactant-like micelles formed in IL/water mixtures.
Atomistic Simulation of the Thermodynamic and Transport Properties of Ionic Liquids
Accounts of Chemical Research, 2007
Atomistic simulations have emerged in recent years as an important compliment to experiment for understanding how the properties of ionic liquids are controlled by their underlying chemical structure. The ability to obtain reliable thermodynamic and transport properties from a simulation depends both on the quality of the force field and on the use of a proper simulation method. Properties such as densities and heat capacities may be obtained readily using standard techniques. With more effort and advanced simulation methods, solid-liquid and vapor-liquid phase equilibria may also be determined. Transport properties can also be computed, but the notoriously slow dynamics of many ionic liquid systems means that great care must be taken to ensure that the simulations are accurate.
Determination of Physical Properties of Ionic Liquids Using Molecular Simulations
2010
Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to
Room temperature ionic liquids containing low water concentrations—a molecular dynamics study
Physical Chemistry Chemical Physics, 2008
We have performed classical molecular dynamics to study the properties of a water-miscible and a water-immiscible room-temperature ionic liquid when mixed with small quantities of water. The two ionic liquids consist of the same 1-ethyl-3-methylimidazolium ([EMIM]) cation combined with either the boron tetrafluoride ([BF 4 ]) or bis(trifluoromethylsulfonyl)imide ([NTf 2 ]) anion. It is found that, in both ionic liquids, water clusters of varying sizes are typically hydrogen bonded to two anions with the cation playing a minor role. We also highlight the difficulties of obtaining dynamic quantities such as self-diffusion coefficients from simulations of such viscous systems.
Nanoscale Heterogeneity and Dynamics of Room Temperature Ionic Liquids
2014
Research Summary: An increase of the alkyl chain length of the cation of room temperature ionic liquids (RTILs) influences the nanoscale structure and dynamics of RTILs, which in turn affect the behavior of RTILs at solid-liquid interfaces central to energy storage devices. We integrate classical molecular dynamics (CMD) simulation, fluorescence correlation spectroscopy (FCS), time resolved fluorescence anisotropy decay (TRFAD,) small angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR) to investigate the fundamental properties including structure, dynamics and interfacial behavior of RTIL electrolytes. We found that the elongation of the alkyl chain in the cation gives rise to an enhanced spatial and dynamical heterogeneity, which have been observed in CMD, FCS, TRFAD and SAXS; CMD combined with NMR has revealed the weak temperature dependence of the dynamics of RTILs at a silica surface due to the surface roughness and strong interaction between the ions and silica w...
Diffusion in ionic liquids: the interplay between molecular structure and dynamics
Soft Matter, 2011
Diffusion in a series of ionic liquids is investigated by a combination of Broadband Dielectric Spectroscopy (BDS) and Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR). It is demonstrated that the mean jump lengths increase with the molecular volumes determined from quantum-chemical calculations. This provides a direct means-via Einstein-Smoluchowski relation-to determine the diffusion coefficient by BDS over more than 8 decades unambiguously and in quantitative agreement with PFG NMR measurements. New possibilities in the study of charge transport and dynamic glass transition in ionic liquids are thus opened.
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.