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.