LAUSR

Abstract Ionic liquids are a special type of synthesized liquids because strong electrostatic force existing between their molecules. Obtaining the strengths of van der Waals and electrostatic forces in ionic liquids is of theoretical significance for synthesizing new ionic liquids, understanding their performances and developing their applications. In this paper, we reported the calculation methods based on Lifshitz theory, Coulomb formula and “four cation–anion pairs cubic unit cell” model for accurately obtaining the strengths of the two forces in five 1-alkyl-3-methylimidazolium ionic liquids. For 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, the relative deviations between the calculated surface tensions and the experimental surface tensions were less than 2%.