Simulation of the surface structure of butylmethylimidazolium ionic liquids

Ruth M Lynden-Bell, Mario Del Popolo

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158 Citations (Scopus)


Molecular dynamics simulations of the liquid/vacuum surfaces of the room temperature ionic liquids [bmim][PF6], [bmim][BF4] and [bmim][Cl] have been carried out at various temperatures. The surfaces are structured with a top monolayer containing oriented cations and anions. The butyl side chains tend to face the vacuum and the methyl side chains the liquid. However, as the butyl chains are not densely packed, both anions and rings are visible from the vacuum phase. The effects of temperature and the anion on the degree of cation orientation is small, but the potential drop from the vacuum to the interior of the liquid is greater for liquids with smaller anions. We compare the simulation results with a range of experimental observations and suggest that neutron reflection from samples with protiated butyl groups would be a sensitive probe of the structure.
Original languageEnglish
Pages (from-to)949-954
Number of pages6
JournalPhysical Chemistry Chemical Physics
Issue number8
Publication statusPublished - Dec 2006

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Atomic and Molecular Physics, and Optics


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