2) with timestep ∆t = 1 ps. A conductivity κ = 5.19 × 10 -8 m 2 /(V • s) was taken from mobility of Na+ in water at 298 K with a charge q = 1 e (e = 1.602 × 10 -19 C). Then, the density is converted into a point by three-dimensional Gaussian fitting. We repeated the above procedure until t = 300 ps.