[gmx-users] Rigid water constraint forces in trajectory output

[Jacob Monroe]

Hi all,

I'm working on calculating radial distribution functions for rigid water
models using force-sampling methods, so I need to know forces on each atom.
When outputting the forces for a simulation trajectory, does GROMACS
include constraint forces? In other words, are the printed forces on each
atom only the derivative of the potential energy? Or do they also include
the force necessary to maintain rigidity of the water molecule? If the
constraint forces are not included, I believe I can calculate them if I
have the forces and velocities and figure out what the rigid body dynamics
should be given the force on each particle. Any thoughts would be very much
appreciated.

Thanks,
Jacob