with ζ zz ≈ 8.1711245653. Note that Equation 9 is indicating that it is particularly favorable to use small system sizes for determining η due to an increased difference between D 0 and D PBC,zz , thus compensating for the loss in accuracy for the self-diffusion coefficients due to the smaller number of molecules. All self-diffusion coefficients are computed from the slope of the center-of-mass mean square displacement (cms-MSD) of the molecules using the Einstein formula according to