# 'No default Proper Dih. types' error

**URL:** <https://gromacs.bioexcel.eu/t/no-default-proper-dih-types-error/7406>\
**Category:** User discussions\
**Tags:** forcefield\
**Created:** [October 16, 2023, 12:35pm UTC](https://gromacs.bioexcel.eu/t/no-default-proper-dih-types-error/7406 "2023-10-16T12:35:23Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![dghyun](https://avatars.discourse-cdn.com/v4/letter/d/ce73a5/32.png) [@dghyun](https://gromacs.bioexcel.eu/u/dghyun)\
**Post date:** [October 16, 2023, 12:35pm UTC](https://gromacs.bioexcel.eu/t/no-default-proper-dih-types-error/7406/1 "2023-10-16T12:35:23Z")

</div>

GROMACS version: 2020.4  
GROMACS modification: Yes (compiled with plumed 2.7.0)  
Force field: charmm36-jul2021.ff

Hi,

I’m trying to perform MD simulation of peptides composed of D-amino acids.  
However, I got the following error when I was trying to add ions to my system.

ERROR 1 [file topol.top, line 1159]:  
No default Proper Dih. types

The corresponding line in the topol.top was the dihedral angle composed of C, CA, CB, and CG atoms in D-glutamic acid.  
In this case, how can I solve this problem?

Thank you in advance!