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Ionic Liquids Room temperature ionic liquids (ILs) have attracted significant attention from scientific and engineering community over the last decade. ILs have been widely investigated for a variety of applications including biphasic systems for separation, solvents for synthetic and catalytic applications, lubricants, lithium batteries, actuators, sensors, reaction media replacement of conventional solvents, active pharmaceutical ingredients, hypergolic propellants, and many other. Importantly, IL properties can be tailored for specific chemical (separation, catalysis, reactions, propellants, explosives) or electrochemical (battery, actuators, supercapacitors) applications by tuning the combination of cations and anions to achieve the desired thermodynamic, solvating and transport properties. The availability of a large number of cations and anions for ILs presents tremendous opportunities for finding optimal cation/anion pairs and IL mixtures for the design of ILs targeted towards specific applications. However, screening a large number of possible cation/anion combinations also presents an enormous challenge for product design as synthesis and characterization of a large number of ILs is expensive. Efficient and reliable predictive tools can speed up the development cycle not only by providing expedient predictions of properties for specific ILs and IL mixtures, but also by providing an improved fundamental understanding of ILs and data needed for the development of empirical structure-property relationship models. Molecular dynamics (MD) simulations are emerging as an excellent complementary (to experiments and empirical correlations) option for reliable prediction of various properties of ILs as well as providing molecular level insight between the structure and properties of ILs. Indeed, most structural, thermodynamic and transport properties of ILs are readily accessible from simulations provided an accurate force field is available. WMI has developed and validated a many-body polarizable APPLE&P force field for ionic liquids containing various number of anions and cations listed below. MD simulations using this force field have been performed on more than 40 ILs and simulation-predicted thermophysical and transport properties were found to be in very good agreement with available experimental data. Particularly striking is the accuracy of predictions of transport properties (self-diffusion coefficient, conductivity, and viscosity) provided by simulations using APPLE&P force field. While most of the simulation studies reported in the literature predict dynamical properties of ILs that are significantly slower than experimental data ( up to an order of magnitude slower), simulations with the APPLE&P predict transport properties within 20-30% percents for majority of ILs. More over, the developed APPLE&P database uses the same repulsion-dispersion nonbonded parameters for the same type atoms in most cases independently of their chemical environment therefore indicating a high transferability of the APPLE&P force field to new compounds. We have extensively utilized MD simulations using APPLE&P force field to study correlations between molecular structure and thrermophysical, transport, and mechanical properties of various ILs in liquid and crystalline phases. Below we list our latest publications in this field. Cations: Anions:
Recent publications: Borodin, O. Polarizable Force Field Development and Molecular Dynamics Simulations of Ionic Liquids. J. Phys. Chem. B 113, 11463-11478 (2009). Borodin, O. A Relation Between Heat of Vaporization, Ion Transport, Molar Volume and Cation-Anion Binding Energy for Ionic Liquids. J. Phys. Chem. B ASAP (2009). Smith, G. D.; Borodin, O.; Salvy, R.; Rees, R.; Hollenkamp, A. F.; A Molecular Dynamics Simulation Study of LiFePO4/Electrolyte Interfaces: Structure and Li+ Transport in Carbonate and Ionic Liquid Electrolytes Chem. Phys. Phys. Chem. 2009. Borodin, O. Molecular Dynamics Simulations of Ionic Liquids: Influence of Polarization on IL Structure and Ion Transport in Materials Research Society Spring Meeting. (ed J.S. Wilkes G.A. Baker, H. Yang) Q06-04 (MRS) Borodin, O. & Smith, G. D. Structure and Dynamics of (N-Methyl-N-Propylpyrrolidinium)+(TFSI)- Ionic Liquid From Molecular Dynamics Simulations. J. Phys. Chem. B 110, 11481-11490 (2006). Borodin, O., Smith, G. D. & Fan, P. Molecular Dynamics Simulations of Lithium Alkyl Carbonates. J. Phys. Chem. B 110, 22773-22779 (2006). Borodin, O. et al. Li+ Transport in Lithium Sulfonylimide-Oligo(ethylene oxide) Ionic Liquids and Oligo(ethylene oxide) Doped with LiTFSI. J. Phys. Chem. B 110, 24266-24274 (2006). Borodin, O., Smith, G. D. & Henderson, W. Li+ Cation Environment, Transport and Mechanical Properties of the LiTFSI Doped N-Methyl-N-Alkylpyrrolidinium+TFSI- Ionic Liquids. J. Phys. Chem. B 110, 16879 -16886 (2006). Smith, G. D., Borodin, O. et al. A comparison of ether- and alkyl-derivatized imidazolium-based room-temperature ionic liquids: a molecular dynamics simulation study. Phys. Chem. Chem. Phys. 10, 6301-6312 (2008). Borodin, O., Smith, G. D. & Kim, H. Viscosity of a Room Temperature Ionic Liquid: Predictions from Nonequilibrium and Equilibrium Molecular Dynamics Simulations. J. Phys. Chem. B 113, 4771-4774 (2009).
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