We want to scan the bond angles of the water molecules to see the effect on the water around them. However, bend is limited to 0-180, and we want to achieve 360°. Is there any way to solve this problem? Thank you for your answer.
The internal coordinate that defines the bend is periodic in pi, so bend angle > 180 deg doesn’t make sense because once it passes through 180 deg, the internal coordinates are computed differently (accesses a different principle value of inverse trig function).
A bigger problem is that your electronic structure is going to break down, due to degeneracies or near-degeneracy of different electronic states, long before you get to 180 deg. Is it really meaningful to stretch the H2O bend that far? Probably requires enough energy to dissociate or electronically excite.