Here D W = D 0 denotes the system size independent true water self-diffusion coefficient. By using the self-diffusion coefficient for water of D W = 2.30 × 10 -9 m 2 s -1 (see Table ), we determine d W = 2.63 nm, which is about 8.5 times the molecular diameter of a water molecule, which can be considered plenty for sampling the long-time diffusion of water.