United-atom force field for [emim][lactate] and molecular simulation of mixture of [emim][lactate] and water

A united-atom force field is developed for ionic liquid 1-ethyl-3-methyl-imidazolium lactate ([emim][lactate]) based on AMBER force field. The refinements mainly include (1) fitting the torsion energy profiles of dihedral angles for obtaining torsion parameters against the data calculated by ab initio calculations; (2) fitting the atomic charges by the one-conformation two-step RESP method. The force field is verified by molecular dynamics simulations for pure ionic liquid and the mixture of [emim][lactate] and water. The densities, excess volume, enthalpies of vaporization, excess molar enthalpy and microstructures are studied. The simulated density is in good agreement with experimental values.