Parametrization of 1-Butyl-3-methylimidazolium Hexafluorophosphate/Nitrate Ionic Liquid for the GROMOS Force Field

Micaêlo, Nuno M.; Baptista, António M.; Soares, Cláudio M.

doi:10.1021/jp061869s

Cited by 132 publications

(154 citation statements)

References 58 publications

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“…To maintain a good transferability of C and N atoms in well-established force field such as CHARMM and AMBER, only the LJ parameters for only two hydrogen atoms (H4 and H5) were adjusted. It is reported 72 that the adjustment of the LJ parameters for anions is an efficient way to improve the force field for ILs. We did not adjust the LJ parameters for the chloride anion because the parameters came from the welldeveloped and widely used Tosi-Fumi potential for molten salts.…”

Section: Lennard-jones Parameters Adjustmentmentmentioning

confidence: 99%

Improved United-Atom Force Field for 1-Alkyl-3-methylimidazolium Chloride

Liu¹,

Chen²,

Bell³

et al. 2010

J. Phys. Chem. B

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We have developed a united atom (UA) nonpolarizable force field for 1-alkyl-3-methyl-imidazolium chloride ([C n mim][Cl], n ) 1, 2, 4, 6, 8), a potential solvent for the pretreatment of lignocellulosic biomass. The charges were assigned by fitting the electrostatic potential surface (ESP) of the ion pair dimers. The LennardJones parameters of the hydrogen atoms on the imidazolium ring were adjusted to agree with the ab initio optimized geometries of isolated ion pairs. Molecular dynamics (MD) simulations were performed for a wide range of temperatures to validate the force field. Substantial improvements were found in both the dynamical properties and the fluid structures, as compared to those predicted using our previously developed UA force field (UA2006) (Phys. Chem. Chem. Phys. 2006, 8, 1096. Liquid densities were found to lie within 2% experimental data. The simulated heats of vaporization decreased about 30% relative to that predicted using the UA2006 force field. The site-site radial distribution functions between the hydrogen atoms on the imidazolium ring and the chloride anions were in good agreement with those determined by ab initio molecular dynamics. The newly developed force field gives a much better description of the self-diffusion coefficients and shear viscosities, which usually deviate by 1 order of magnitude when determined using other force fields.

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Section: Lennard-jones Parameters Adjustmentmentmentioning

confidence: 99%

Improved United-Atom Force Field for 1-Alkyl-3-methylimidazolium Chloride

Liu¹,

Chen²,

Bell³

et al. 2010

J. Phys. Chem. B

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“…Certain efforts have been recently made to improve the situation, including the decrease of electrostatic charges 48,49 , fine tuning both sigmas and epsilons for selected interaction sites 50,51 , tuning bonded interactions to reproduce newly obtained experimental properties 46 . Unfortunately, most of these refinements are quite artificial and do not have a strong physical background.…”

Section: Introductionmentioning

confidence: 99%

Polarizability versus mobility: atomistic force field for ionic liquids

Chaban

2011

Phys. Chem. Chem. Phys.

155

182

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Based on classical molecular dynamics simulations, we discuss the impact of Coulombic interactions on a comprehensive set of properties of room temperature ionic liquids (RTILs) containing 1,3-dimethylimidazolium (MMIM + ), N-butylpyridinium (BPY + ), and bis(trifluoromethane sulfonyl)imide (TFSI -) ions. Ionic transport is found to be noticeably hindered by the excessive Coulombic energy, originating from the neglect of electronic polarization in the condensed phase of these RTILs. Starting from the models, recently suggested by Lopes and Padua, we show that realistic ionic dynamics can be achieved by the uniform scaling of electrostatic charges on all interaction sites. The original model systematically overestimates density and heat of vaporization of RTILs. Since density linearly depends on charge scaling, it is possible to use it as a convenient beacon to promptly derive a correct scaling factor. Based on the simulations of [BPY][TFSI] and [MMIM][TFSI] over a wide temperature range, we conclude that suggested technique is feasible to greatly improve quality of the already existing non-polarizable FFs for RTILs.

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“…This is conveniently done by comparing simulated and experimental results of selected properties, like density, conductivity, viscosity or isothermal compressibility. [24][25][26][27][28][29][30][31][32] Alternatively, spectroscopic data, 22,33,34 computed properties like the heat of vaporization, [29][30][31][32]35 or quantum-mechanical calculations can be used. 36,37 In this work, we propose another check for the validity of a chosen computational force field: the frequency-dependent dielectric spectrum, which monitors rotational and translational motions over several orders of magnitude in frequency space.…”

Section: Introductionmentioning

confidence: 99%

The influence of polarizability on the dielectric spectrum of the ionic liquid 1-ethyl-3-methylimidazolium triflate

Schröder

Sonnleitner

Buchner

et al. 2011

Phys. Chem. Chem. Phys.

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This work reports for the first time the computational, frequency-dependent dielectric spectrum of the polarizable molecular ionic liquid 1-ethyl-3-methylimidazolium triflate as well as its experimental analogue. In the frequency range from 500 MHz up to 20 GHz the agreement between the computational and the experimental spectrum is quantitative. For higher frequencies up to 10 THz the agreement is still remarkably good. The experimental asymptotic limit e N is 2.3. The difference in the computational value of 1.9 comes solely from the neglect of polarizability of the hydrogen atoms. For reasons of efficiency the simulations are based on the Lagrangian algorithm for the Drude oscillator model which cannot handle polarizable hydrogens. In the computational analysis the complete spectrum of the generalized dielectric constant P Ã 0 ðnÞ is splitted into its translational and non-translational components, called dielectric conductivity W 0 (n) and dielectric permittivity e(n). For 1-ethyl-3-methylimidazolium triflate both components contribute with equal weight and overlap in the complete frequency range. The inclusion of polarization forces, however, is quite different for the two components: the collective non-translational dynamics is accelerated and hence the dielectric permittivity is shifted to higher frequencies. The low frequency region of the dielectric conductivity is also affected while its high frequency part remains almost unchanged. Inductive effects are not only visible at high frequencies but also contribute in the sub-GHz region. The computational peak found in this region correlates with the experimental OKE-spectrum. It may be interpreted as the correlation between the induced dipole moment of the cations and the local electric field exerted by the anionic cage.

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Parametrization of 1-Butyl-3-methylimidazolium Hexafluorophosphate/Nitrate Ionic Liquid for the GROMOS Force Field

Cited by 132 publications

References 58 publications

Improved United-Atom Force Field for 1-Alkyl-3-methylimidazolium Chloride

Improved United-Atom Force Field for 1-Alkyl-3-methylimidazolium Chloride

Polarizability versus mobility: atomistic force field for ionic liquids

The influence of polarizability on the dielectric spectrum of the ionic liquid 1-ethyl-3-methylimidazolium triflate

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