# Grompp - no proper dihedral types error **URL:** \ **Category:** User discussions\ **Created:** [December 9, 2022, 1:51am UTC](https://gromacs.bioexcel.eu/t/grompp-no-proper-dihedral-types-error/5394 "2022-12-09T01:51:36Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![hp219](https://avatars.discourse-cdn.com/v4/letter/h/dfb087/32.png) [@hp219](https://gromacs.bioexcel.eu/u/hp219)\ **Post date:** [December 9, 2022, 1:51am UTC](https://gromacs.bioexcel.eu/t/grompp-no-proper-dihedral-types-error/5394/1 "2022-12-09T01:51:36Z")
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. ---
**Author:** ![hp219](https://avatars.discourse-cdn.com/v4/letter/h/dfb087/32.png) [@hp219](https://gromacs.bioexcel.eu/u/hp219)\ **Post date:** [December 9, 2022, 2:14am UTC](https://gromacs.bioexcel.eu/t/grompp-no-proper-dihedral-types-error/5394/2 "2022-12-09T02:14:50Z")
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