Simulation and QENS studies of molecular dynamics in aqueous solutions of 1,2-dimethoxyethane

We compare the composition dependence of the self-diffusion coefficient of water in aqueous solutions of 1,2-dimethoxyethane (DME) as obtained from incoherent quasielastic neutron scattering measurements and molecular dynamics simulations. Simulations were performed using the TIP4P water model and a quantum chemistry based potential for DME and DME/water interactions. Excellent agreement is seen between experiment and simulation, including the minimum in the water self-diffusion coefficient at X-DME approximate to 0.2 predicted by our earlier simulations. Further, we investigated the influence of the water potential on molecular dynamics in DME aqueous solutions by performing simulations using the SPC, SPC/E, and MCY water models. The SPC and MCY models yielded a water self-diffusion coefficient as a function of composition in qualitative agreement with experiment, including the before mentioned minimum. Quantitative agreement with experiment is poorer for these potentials than for the TIP4P model. Surprisingly, simulations employing the SPC/E model, known to provide the best description of self-diffusion in pure water, showed a qualitatively incorrect dependence of water self-diffusion on composition. The failure of the SPC/E water model was attributed to overestimation of the strength of water-water interactions.