Does the addition of heteropoly acid changes the water percolation threshold of PFSA membranes? S. Akbari a , M. T. Hamed Mosavian a , F. Moosavi b and A. Ahmadpour a a Chemical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Iran b Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Iran Supporting Information Figure S1. The Kegging and Anderson-Evans anions. Oxygen (red), Tungsten (blue), Phosphorus (yellow), Aluminum (purple), Iodine (Brown). Prior to MD simulation, the structure of HPA particles was optimized by DFT calculation at B3LYP/LANL2DZ level of theory using Gaussian 09 software [1]. The partial charge of the HPA anions were obtained by ChelpG method [2]. In order to obtain the initial configuration for MD simulation, each system was minimized by the steepest descent algorithm [3]. Then, the following procedure was implemented until each system reaches to stabile equilibrium and thus final density was calculated; (1) NPT MD simulation with T=600 K and P=1 MPa. It should be noted that the value of ε for Nafion is reduced to 1/100 magnitude at this step. (2) NPT MD simulation in which the Lennard- Jones (LJ) potential parameters were returned to the normal values at T=300 K and P=101.325 kPa for 100 ps. (3) NPT MD simulations with temperature variation between 300 K and 600 K and Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is © the Owner Societies 2019