[gmx-users] TIP4ew water and velocities on dummy atoms

[Antila Hanne]

Dear experts,

I converted a trajectory (.trr) containing a simulation of tip4ew water  to .gro format. In the resulting .gro file, there are velocities also for the tip4 virtual sites MW. This confuses me, since these sites have no mass. How is this velocity calculated? I have been under the impression that, at each step, the coordinates of MW are merely assigned based on the coordinates of the rest of the water atoms.

Help will be appreciated!

Yours,

Hanne Antila

PhD candidate,
Aalto University