Polarizable force field for water-dimethyl sulfoxide systems: II properties of mixtures by molecular dynamics simulations

A consistent polarizable force field for dimethyl sulfoxide (DMSO) with the TIP4P-FQ (fluctuating charge) water model was developed to explore the properties of pure DMSO liquid and the DMSO-water mixtures in this work. The DMSO-water mixtures at a range of concentrations of DMSO were selected to explore the unusual properties of them at 298 K and 1 atm. The radial distribution functions of neat DMSO liquid from the simulations with the current model are more excellently consistent with data from a neutron diffraction experiment than the additive models. More reasonable results for the static (radial distribution function, density, excess volume, heat of vaporization and mixing heat) and dynamic properties (lifetime of hydrogen bond, reorientational relaxation time and self-diffusion coefficient) of the mixtures over a range of composition were obtained by the current model and parameters than the previous additive models. The interaction between methyl hydrogen and water oxygen is mainly characteristic of weak hydrogen bond interactions and weaker than that between methyl hydrogen and DMSO oxygen. The hydrated methyl is more preferred than the methyl-methyl association. The enhanced structure of water and DMSO within the first shell is due to decrease of the water number in the hydrogen bond chain of DMSO-nwater-DMSO. The distributions and fluctuations of dipole moment can well reflect the polarization effect and the microscopic configures in the mixtures. The static dielectric permittivities of the DMSO-water mixtures are in well agreement with the corresponding experimental values.