Viscosity of liquid water from computer simulations with a polarizable potential model

The longitudinal and shear viscosity of water are calculated by molecular dynamics simulation with a polarizable potential model at room temperature. To overcome the difficulty of evaluating directly the stress autocorrelation function of a system with intrinsically many-body forces, we have resorted to the analysis of the wave-vector-dependent longitudinal and transverse-current correlation functions. In a memory function formalism, the generalized viscosity can be evaluated as a function of the wave vector k. By extrapolating to k=0, we find longitudinal and shear viscosity values in better agreement with the experimental value than the corresponding quantities evaluated by making use of a nonpolarizable potential model. This result points out that for a realistic reproduction of transport quantities, it is crucial to take into account many-body contributions to the interaction potential.