Cation self-diffusion coefficients were calculated from the production trajectories as the mean square displacement ⟨MSD(t)⟩ at the center of mass of the molecule. To ensure that all the systems studied reached the diffusive regime, the slope of the MSD log-log plot was calculated for each system using the last 5 ns of simulation. In all cases, a slope of 1 was obtained (examples shown in Figure ). Box-size effects corrections have been included using the procedure reported by Yeh and Hummer. 44