Determination of the distance-dependent viscosity of mixtures in parallel slabs using non-equilibrium molecular dynamics

We generalize a technique for determination of the shear viscosity of mixtures in planar slabs using non-equilibrium computer simulations by applying an external force parallel to the surface generating Poiseuille flow. The distance-dependent viscosity of the mixture, given as a function of the distance from the surface, is determined by analysis of the resulting velocity profiles of all species. We present results for a highly non-ideal water + methanol mixture in the whole concentration range between rutile (TiO2) walls. The bulk results are compared to the existing equilibrium molecular dynamics and experimental data while the inhomogeneous viscosity profiles at the interface are interpreted using the structural data and information on hydrogen bonding.