53 Thus, the t of Eq. ( ) to the D PBC values calculated from the simulation as a function of simulation box size L has two free parameters, namely D ∞ and µ m , both of which are free of nite size eects and can thus be compared to experiment. The inter-leaet friction coecient does not appear in Eq. ( ) as we expect it to be innite, which was found to be a valid assumption for lipid bilayers. 53 The water viscosity value of µ f = 0.3228 mPa•s was interpolated to 298 K from the values for CHARMM TIP3P in Ref. and used for all simulations (CHARMM TIP3P and normal TIP3P dier by ∼23%). The simulation box dimensions (membrane edge length L and the dimension normal to the membrane plane (z) L z ) were taken from the nal conguration of each simulation. L z was only needed in the calculation of H (see below). Membrane thickness h was obtained as described in Structural properties above.