Development of OPLS-AA force field parameters for 68 unique ionic liquids

Somisetti V. Sambasivarao, Orlando Acevedo

Research output: Contribution to journalArticlepeer-review

310 Scopus citations


OPLS-AA force field parameters have been developed and validated for use in the simulation of 68 unique combinations of room temperature ionic liquids featuring 1-alkyl-3-methylimidazolium [RMIM] (R = Me, Et, Bu, Hex, Oct), N-alkylpyridinium [RPyr], and choline cations, along with Cl -, PF 6 -, BF 4 -, NO 3 -, AlCl 4 -, Al 2Cl 7 -, TfO -, saccharinate, and acesulfamate anions. The new parameters were fit to conformational profiles from gas-phase ab initio calculations at the LMP2/cc-pVTZ(-f)//HF/6-31G(d) theory level and compared to experimental condensed-phase structural and thermodynamic data. Monte Carlo simulations of the ionic liquids gave relative deviations from experimental densities of ca. 1-3% at 25 °C for most combinations and also yielded close agreement over a temperature range of 5 to 90 °C. Predicted heats of vaporization compared well with available experimental data and estimates. Transferability of the new parameters to multiple alkyl side-chain lengths for [RMIM] and [RPyr] was determined to give excellent agreement with charges and torsion potentials developed specific to desired alkyl lengths in 35 separate ionic liquid simulations. As further validation of the newly developed parameters, the Kemp elimination reaction of benzisoxazole via piperidine was computed in 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF 6] using mixed quantum and molecular mechanics (QM/MM) simulations and was found to give close agreement with the experimental free energy of activation.

Original languageEnglish (US)
Pages (from-to)1038-1050
Number of pages13
JournalJournal of Chemical Theory and Computation
Issue number4
StatePublished - Apr 14 2009
Externally publishedYes

ASJC Scopus subject areas

  • Computer Science Applications
  • Physical and Theoretical Chemistry


Dive into the research topics of 'Development of OPLS-AA force field parameters for 68 unique ionic liquids'. Together they form a unique fingerprint.

Cite this