[gmx-users] Request on initial velocities

[Riccardo Conte]

Dear Gromacs users,

I am experiencing an issue in trying to perform a dynamics run by feeding in my own starting velocities. My procedure is as in the following:

1) I build my .gro file with the desired starting position and velocities;
2) I choose the flag "no" for the "gen-vel" option in the .mdp file;
3) I run my dynamics with the md-vv-avek integrator because I am interested in a NVE simulation (no thermostat).

Once I get the outcome of the dynamics run, I can notice that the velocities at the initial step are different from those I passed to the program.
Is there a way to fix this issue? Am I wrong in one of the previously listed steps?

Many thanks,

SEMICOMPLEX