Virtual Site OPLS Force Field for Imidazolium-Based Ionic Liquids

Brian Doherty, Xiang Zhong, Orlando Acevedo

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Molecular simulations of ionic liquids can provide deeper insight into the relationship between intermolecular interactions and macroscopic measurements for the solvents. However, many existing force fields have multiple shortcomings, including poor solvent dynamics, the underestimation of hydrogen-bonding strength, and errors in solvent interactions/organization. A new force field, called optimized potentials for liquid simulation-ionic-liquid virtual site (OPLS-VSIL), has been developed for imidazolium-based ionic liquids featuring a novel topology incorporating a virtual site bisecting the nitrogen atoms that offloads negative charge to inside the plane of the ring. Guided by free energy of hydration calculations, an empirically derived set of partial charges and nonbonded Lennard-Jones terms for both 1-alkyl-3-methylimidazolium and 11 different anions provided accurate bulk-phase ionic-liquid properties and produced radial distribution functions nearly indistinguishable from ab initio molecular dynamics simulations. For example, overall mean absolute errors (MAEs) of 3.1-3.4% were computed for the density, heat of vaporization, and viscosity of approximately 20 different ion pair combinations. Additional physical properties, such as, self-diffusion coefficients, heat capacity, and surface tension also gave significant MAE improvements using OPLS-VSIL compared to the existing fixed-charge ionic-liquid force fields. Local interactions, including cation-anion hydrogen bonding and π-π stacking between the imidazolium rings, were also accurately reproduced.

Original languageEnglish (US)
Pages (from-to)2962-2974
Number of pages13
JournalJournal of Physical Chemistry B
Volume122
Issue number11
DOIs
StatePublished - Mar 22 2018

Fingerprint

Ionic Liquids
Ionic liquids
field theory (physics)
liquids
Hydrogen Bonding
Anions
Hydrogen bonds
Negative ions
Hot Temperature
Volatilization
Surface Tension
anions
heat of vaporization
Molecular Dynamics Simulation
Vaporization
Viscosity
simulation
Hydration
rings
Free energy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

Virtual Site OPLS Force Field for Imidazolium-Based Ionic Liquids. / Doherty, Brian; Zhong, Xiang; Acevedo, Orlando.

In: Journal of Physical Chemistry B, Vol. 122, No. 11, 22.03.2018, p. 2962-2974.

Research output: Contribution to journalArticle

Doherty, Brian ; Zhong, Xiang ; Acevedo, Orlando. / Virtual Site OPLS Force Field for Imidazolium-Based Ionic Liquids. In: Journal of Physical Chemistry B. 2018 ; Vol. 122, No. 11. pp. 2962-2974.
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