[gmx-users] Angle constraints independent on bond constraints

[Fabian Gottwald]

Dear all,

I want to study vibrational dynamics and have an HDO molecule
(D: Deuterium) in a bulk water surrounding as a test case.
In a test calculation I want to fix the OD bond and the HOD angle
whereas the OH bond shall be allowed to vibrate.
Fixing the OD bond is no problem but the angle constraints seem
to be more problematic. So far I have found in the manual and in
previous posts that fixing the angle amounts to fixing the whole
triangle via bond constraints which is not suitable for my purpose.
Is there any chance to do angle constraints for a particular
molecule independent on bond constraints?

Greetings
Fabian Gottwald