where x i (t) is the instantaneous position of i th particle at time t and N is the number of particles. The numerator is mean-squared displacement (MSD) of a molecule center of mass during time t and ⟨...⟩ denotes an ensemble average. Note that we performed both configuration averaging and time-origin averaging using a sliding-window strategy. The relation only holds for the Fickian regime of the MSD curve, therefore, it is necessary to reach the diffusive linear regime to extract an accurate diffusion coefficient. With the diffusion coefficients for mobile species obtained from MSD, we first calculate the ionic conductivity with the Nernst-Einstein equation, which states that the total conductivity is proportional to individual diffusion coefficient and ionic concentration: