# Ions.tpr file

**URL:** <https://gromacs.bioexcel.eu/t/ions-tpr-file/1234>\
**Category:** User discussions\
**Created:** [December 9, 2020, 8:10am UTC](https://gromacs.bioexcel.eu/t/ions-tpr-file/1234 "2020-12-09T08:10:01Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Hossein](https://avatars.discourse-cdn.com/v4/letter/h/9de0a6/32.png) [@Hossein](https://gromacs.bioexcel.eu/u/Hossein)\
**Post date:** [December 9, 2020, 8:10am UTC](https://gromacs.bioexcel.eu/t/ions-tpr-file/1234/1 "2020-12-09T08:10:01Z")

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GROMACS version:  
GROMACS modification: Yes/No  
Hi  
I work on ligand receptor simulation by gromacs.  
i did step by step stages tutorial complex ligand protein simulation with charm forcefield 36. Ligand str file constructed by website CGENFf. In step construct ions.tpr file i received error  
ERROR 1 [file ligand.itp, line 540]:  
No default Proper Dih. types.  
How can i solve it?

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [December 9, 2020, 2:20pm UTC](https://gromacs.bioexcel.eu/t/ions-tpr-file/1234/2 "2020-12-09T14:20:38Z")

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You likely didn’t `#include` the `.prm` file that the ligand requires, which contains the new bonded parameters used by the ligand.