Molecular simulations of imidazolium-based tricyanomethanide ionic liquids using an optimized classical force field

Vergadou, Niki; Androulaki, Eleni; Hill, Jörg‐Rüdiger; Economou, Ioannis G.

doi:10.1039/c5cp05892a

Cited by 16 publications

(26 citation statements)

References 76 publications

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“…Cyano-based ILs have a significantly lower viscosity than fluorine-based ILs, making them more attractive for industrial applications. 42 These systems have been used in several studies focused on dye-sensitized solar cells, 43,44 53 The calculated transport properties were found to be in very good agreement with the experiments. 53 Also, very lately [C 2 mim][TCM] and its mixtures with water were simulated.…”

Section: Introductionsupporting

confidence: 56%

“…58 As explained above, the higher structural organization efficiency resulted from the higher dispersive interactions present in the fluorinated ILs leads to an increase of the density with increasing the molar weight/molar volume of the anion. For the case of cyano-based ILs, the decrease of the density with the increase of the molar mass/molar volume of the anion is related to differences in structural organization, which are also depicted in RDFs calculated from molecular simulation 17,53 ( À -based ILs, while for the cation-cation analysis a small peak at about 6 Å is observed. The tendency for chain aggregation phenomena is also slightly higher for this IL family ( Fig.…”

Section: Densitymentioning

confidence: 99%

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

Zubeir

Rocha

Vergadou

et al. 2016

Phys. Chem. Chem. Phys.

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The low-viscous tricyanomethanide ([TCM]À )-based ionic liquids (ILs) are gaining increasing interest as attractive fluids for a variety of industrial applications. The thermophysical properties (density, viscosity, surface tension, electrical conductivity and self-diffusion coefficient) of the 1-alkyl-3-methylimidazolium tricyanomethanide [C n mim][TCM] (n = 2, 4 and 6-8) IL series were experimentally measured over the temperature range from 288 to 363 K. Moreover, a classical force field optimized for the imidazolium-based[TCM] À ILs was used to calculate their thermodynamic, structural and transport properties (density, surface tension, self-diffusion coefficients, viscosity) in the temperature range from 300 to 366 K. The predictions were directly compared against the experimental measurements. The effects of anion and alkyl chain length on the structure and thermophysical properties have been evaluated. In cyano-based ILs, the density decreases with increasing molar mass, in contrast to the behavior of the fluorinated anions, being in agreement with the literature. The contribution per -CH 2 -group to the increase of the viscosity presents the following sequence: The experimentally determined self-diffusion coefficients of the cations are in good agreement with the molecular simulation predictions, in which a decrease of the self-diffusion of the cations with increasing alkyl chain length is observed with a simultaneous increase in viscosity and for the longer alkyl lengths the anion becomes more mobile than the cation.

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Section: Introductionsupporting

confidence: 56%

Section: Densitymentioning

confidence: 99%

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

Zubeir

Rocha

Vergadou

et al. 2016

Phys. Chem. Chem. Phys.

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“…As discussed earlier, scaling the partial charges of ions by a uniform factor is an effective way to represent charge-transfer effects at reduced computational cost. This method has been shown to enhance the dynamics and improve the transport coefficients of simulated systems , and give better agreement with experiments. ,, However, determination of the charge-scaling factor to use is not straightforward. , …”

Section: Resultsmentioning

confidence: 99%

Structural and Transport Properties of Tertiary Ammonium Triflate Ionic Liquids: A Molecular Dynamics Study

Nasrabadi

Gelb

2017

J. Phys. Chem. B

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Ammonium-based protic ionic liquids (PILs) have shown promising physicochemical properties as proton conductors in polymer membrane fuel cells. In this work, molecular dynamics simulations are used to study the structural, dynamic, and transport properties of a series of tertiary ammonium triflate PILs. Nonpolarizable all-atom force fields were used, including two different models for the triflate anion. Previous simulation studies of these PILs have yielded poor results for transport properties due to unrealistically slow dynamics. To improve performance, polarization and charge-transfer effects were approximately accounted for by scaling all atomic partial charges by a uniform factor, γ. The optimum scaling factor γ = 0.69 was determined by comparing simulation results with available experimental data and found to be transferable between different ammonium cations and insensitive to both the temperature and choice of experimental data used for comparison. Simulations performed using optimized charge scaling showed that the transport properties significantly improved over previous studies. Both the self-diffusion coefficients and viscosity were in good agreement with experiment over the whole range of systems and temperatures studied. Simulated PIL densities were also in good agreement with experiment, although the thermal expansivity was underestimated. Structural analysis revealed a strong directionality in interionic interactions. Triflate anions preferentially approach the ammonium cation so as to form strong hydrogen bonds between sulfonate oxygen atoms and the acidic ammonium hydrogen. The ionic conductivity was somewhat underestimated, especially at lower temperatures. Analysis of conductivity data suggests that there is significant correlated motion of oppositely charged ions in these PILs, especially at short times. These results overall indicate that the transport properties of this class of PILs are accurately modeled by these force fields if charge scaling is used and properly calibrated against selected experimental data.

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“…We give the simulation parameters that reproduce the studied IL/silica interface. Detailed information about the force field parameters of the bulk IL are given elsewhere . In section , we present our results and propose a model for the interpretation of the observed behavior.…”

Section: Introductionmentioning

confidence: 87%

“…The set of force field parameters that was used is presented in ref . Charge distributions for both ions were calculated quantum mechanically (QM) using various schemes and the anion parameters were determined . A total ionic charge of ±0.75e was introduced in this force field as dictated by the QM calculations.…”

Section: Simulation Detailsmentioning

confidence: 99%

Molecular Dynamics Simulation of Highly Confined Glassy Ionic Liquids

2016

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We present a molecular dynamics simulation study of 1-octyl-3-methylimidazolium tricyanomethanide ([Omim+][TCM–]) ionic liquid capped by two silica planar surfaces. The study extends over a wide temperature range and various interwall distances. Our results indicate that the structure and dynamics of the confined system is significantly affected by the width of the film. At the shortest interwall distance of 25 Å, which is comparable to the ion pair dimensions, the bulk structure is breached. The dynamics of the cation in the adsorbed layer is accelerated for the time scale of 1 ns and decelerates for longer time scales. In the most confined film, we observe a suppression of the cooperative characteristics in the diffusion. The whole phenomenon seems to be related to an Arrhenius behavior. Our proposed model suggests a stable, static liquid path in the center of the pore that facilitates the diffusion. The simulations results are consistent with a recent experimental study on the same confined system.

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Molecular simulations of imidazolium-based tricyanomethanide ionic liquids using an optimized classical force field

Cited by 16 publications

References 76 publications

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

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

Structural and Transport Properties of Tertiary Ammonium Triflate Ionic Liquids: A Molecular Dynamics Study

Molecular Dynamics Simulation of Highly Confined Glassy Ionic Liquids

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