MOLECULAR DYNAMICS SIMULATION ON THE STRUCTURE AND DYNAMICS OF WATER IN THE 1-BUTYL-3-METHYLIMIDAZOLIUM TETRAFLUOROBORATE/WATER MIXTURE

The micro-structure, and IR spectrum of water molecules in 1-butyl-3-methylimidazolium tetrafluoroborate([ Bmim] BF4)/water mixture with different concentrations (x(1) = 25.0%, 50.0%, 75.0%, and 90.0%) were studied with molecular dynamics simulation at room temperature. It was shown that water molecules tend to be isolated from each other in mixtures with more ions than water molecules in pure water. With the increase of the molar fraction of water in the mixture, the rotation bands and the bending bands of water display red shift from 566.2 to 651.4 cm(-1) and from 1638.4 to 1683.2 cm(-1) respectively, whereas the O-H stretch bands show blue shift from 3519.8 to 3452 cm(-1), which agree well with the experimental results. This suggests that the molecules are hindered and their motions are difficult and slow, due to the hydrogen-bond interactions and the inharmonic interactions between the inter-or intra-molecular modes of water molecules.