Local viscosity change in water near a solid-liquid interface and its extraction by means of molecular rotational diffusion - A molecular dynamics study

The relation between the rotational diffusion (RD) coefficient of water molecules and viscosity, that theoretically are inversely proportional to each other, was examined by using molecular dynamics simulations. In a homogeneous bulk liquid system, both the viscosity calculated from the virial theorem and the experimental one correlated well with the inverse of water RD coefficient at various temperatures. In a heterogeneous system of water between solid walls with different solid-liquid interaction strength, the viscosity distribution was similar to the distribution of the RD coefficient inverse multiplied by density, and this suggests the possibility of extracting nanometer-scale viscosity distribution by RD.