Polarizable Force Field Development and Molecular Dynamics Simulations of Ionic Liquids

Abstract

A many-body polarizable force field has been developed and validated for ionic liquids (ILs) containing 1-methyl-3-alkylimidazolium, 1-alkyl-2-methyl-3-alkylimidazolium, N-methyl-N-alkylpyrrolidinium, N-alkylpyridinium, N-alkyl-N-alkylpiperidinium, N-alkyl-N-alkylmorpholinium, tetraalkylammonium, tetraalkylphosphonium, N-methyl-N-oligoetherpyrrolidinium cations and BF(4)(-), CF(3)BF(3)(-), CH(3)BF(3)(-), CF(3)SO(3)(-), PF(6)(-), dicyanamide, tricyanomethanide, tetracyanoborate, bis(trifluoromethane sulfonyl)imide (Ntf(2)(-) or TFSI(-)), bis(fluorosulfonyl)imide (FSI(-)) and nitrate anions. Classical molecular dynamics (MD) simulations have been performed on 30 ionic liquids at 298, 333, and 393 K. The IL density, heat of vaporization, ion self-diffusion coefficient, conductivity, and viscosity were found in a good agreement with available experimental data. Ability of the developed force field to predict ionic crystal cell parameters has been tested on four ionic crystals containing Ntf(2)(-) anions. The influence of polarization on the structure and ion transport has been investigated for [emim][BF(4)] IL. A connection between the structural changes in IL resulting from turning off polarization and slowing down of ion dynamics has been found. Developed force field has also provided accurate description/prediction of thermodynamic and transport properties of alkanes, fluoroalkanes, oligoethers (1,2-dimethoxyethane), ethylene carbonate, propylene carbonate, dimethyl carbonate, hydrazine, methyhydrazine, dimethylhydrazine, acetonitrile, dimethyl amine, and dimethyl ketone.

Dispersion interactions in room-temperature ionic liquids: Results from a non-empirical density functional

“…However, the PBE binding energy is quite small precisely due to the lack of dispersion interactions. The good agreement in geometries is probably due to the well known trend of GGA to underbind 50 and study of their performance will be addressed in the future. The LDA, as usual, produces distances that are significantly shorter than all other approaches, including the FF.…”

Including many-body effects in models for ionic liquids

“…Apart from the intrinsic interest for such systems, they have been studied by computer simulations in many contexts. For example, molten oxides are the main components of magmatic melts [3][4][5][6] , molten fluorides and chlorides are investigated for their importance in many metallurgical processes [7][8][9] and for their potential use in the nuclear industry 10,11 , and room temperature ionic liquids for their use in electrochemical storage applications [12][13][14] or their solvation properties [15][16][17] .…”

Communication: Probing the existence of partially arrested states in ionic liquids

“…The comparison between simulation and experiments may be improved upon using polarizable force fields, for which the net effect is that the system becomes more mobile. [31][32][33] However, the complexity of the force fields is surely not affecting the observation of anomalous diffusion of RTIL.…”