From: Ethan Croitoru (
Date: Wed Aug 05 2020 - 10:23:49 CDT


I have a NAMD simulation (i.e. dcd and psf files), and would like to use
some of GROMACS trajectory analysis commands. In order to do so I need a
sudo .tpr file, one that's good enough for analysis, but won't work for
simulation. I have been following the steps outlined here:
So I have a .top file from using the vmd plugin topo (, but when I try to
execute this gmx grompp command:

gmx grompp -f sample.mdp -c structure.pdb -p -o simulation.tpr

I get:

Fatal error:
Unknown cmap torsion between atoms 13 15 17 23 25

I have seen this can be an issue with the .top file used, so to create that
I ran:

topo writegmxtop

with the psf and pdb files loaded into vmd. From my understanding, I don't
need to add parameter files since I won't be running simulations with these
Any help with this error would be appreciated.