Fig. 6 In (a), V1 is the unit vector normal to the surface. V2 is the vector pointing from O to the H atom (OH bond angle). θ is the angle between the two vectors. In (b), we show the OH bond angle for all water molecules for different pore widths in H-H and P-H pores. In P-H pores, a dominant angle of 130° is observed while in H-H 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.