Fig. 6 In (a), V1 is the unit normal vector. V2 is the OH vector (OH bond angle). θ is the angle between two vectors. In (b), we show the OH bond angle for all water molecules for different pore widths in HH and PH pores. In PH pores, a dominant angle of 130° is observed while in HH pores, the OH bond angles are largely random with a weaker peak at 90°. The electric field of Fig. 5 influences the orientation of water molecules in both pore systems.