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 in coherent quasielastic neutron scattering measurements and molecular dynamic s simulations. Simulations were performed using the TIP4P water model and a quantum chemistry based potential for DME and DME/water interactions. Exce llent agreement is seen between experiment and simulation, including the mi nimum in the water self-diffusion coefficient at X-DME approximate to 0.2 p redicted by our earlier simulations. Further, we investigated the influence of the water potential on molecular dynamics in DME aqueous solutions by p erforming simulations using the SPC, SPC/E, and MCY water models. The SPC a nd MCY models yielded a water self-diffusion coefficient as a function of c omposition in qualitative agreement with experiment, including the before m entioned minimum. Quantitative agreement with experiment is poorer for thes e 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-diff usion on composition. The failure of the SPC/E water model was attributed t o overestimation of the strength of water-water interactions.