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. (C) 2009 Elsevier B.V. All rights reserved.