Grompp - no proper dihedral types error

User discussions
1

GROMACS version: 2021.3
GROMACS modification: No

Hi, I generated a new topology on the CGenFF server to use with the CHARMM36 forcefield (most recent version of each was used). I’ve been able to build my system fine, but I got the following error when running grompp prior to energy minimisation:

ERROR 1 [file topol.top, line 393]:

No default Proper Dih. types

The corresponding atoms in the dihedral have the types NG321, CG321, CG321, and CG321, respectively.

I’ve tried having a look through ffbonded.itp, but there wasn’t anything I found for this combination of atom types - I guess this is what the error is. Also, I’ve had a look at the charmm2gmx findmissingpars.py, but I am not familiar enough with Python to really understand how/if I could get parameters from this.

Any help would be appreciated!

Many thanks.

2

I’ve managed to fix this issue. It turns out it was a simple case of not reading properly through the .str file output from CGenFF which had this dihedral in all along!!
CG321 CG321 CG321 NG321 9 0.000000 0.300000 3