Given the start configuration (.pdb), topology file (topol.top) and run file(water.mdp). I want to generate the forces on atoms. I tried, using:

gmx grompp -f water.mdp -c water_1.gro -p topol.top -o water.tpr -maxwarn 2
gmx traj -f water_1.gro -s water.tpr -of force.xvg -ox coords.xvg

However, the forces.xvg file turned up empty. What are my other alternatives here?

P.S. I used charmm force-field.

  • 1
    $\begingroup$ I think you need to run your simulation with gmx mdrun for 1 step and make sure nstfout=1 in your mdp file. Forces will then be available in the trajectory output file. $\endgroup$
    – Hayden S
    Commented Mar 18, 2022 at 11:49
  • $\begingroup$ This question seems to be abandoned. It can be reopened if OP addresses questions/suggestions in the comments or if someone would like to provide an answer. $\endgroup$
    – Tyberius
    Commented Apr 12, 2022 at 14:35