# Problem in generation of ions.tpr file in protein-ligand complex. Can anyone help please?

**URL:** <https://gromacs.bioexcel.eu/t/problem-in-generation-of-ions-tpr-file-in-protein-ligand-complex-can-anyone-help-please/7523>\
**Category:** User discussions\
**Created:** [November 1, 2023, 8:12am UTC](https://gromacs.bioexcel.eu/t/problem-in-generation-of-ions-tpr-file-in-protein-ligand-complex-can-anyone-help-please/7523 "2023-11-01T08:12:42Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Ishpiya](https://avatars.discourse-cdn.com/v4/letter/i/fbc32d/32.png) [@Ishpiya](https://gromacs.bioexcel.eu/u/Ishpiya)\
**Post date:** [November 1, 2023, 8:12am UTC](https://gromacs.bioexcel.eu/t/problem-in-generation-of-ions-tpr-file-in-protein-ligand-complex-can-anyone-help-please/7523/1 "2023-11-01T08:12:42Z")

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GROMACS version: 2023  
GROMACS modification: No  
Here post your question  
In protein-ligand complex, when I am trying to create ions.tpr file with the command gmx grompp -f ions.mdp -c solv.gro -p topol.top -o ions.tpr  
It is showing error in unk.itp file. I am using charmm36-jul2022 forcefield .

 ![IMG_2569](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/2/2a4fe8f4577efbc3f904678770893a9f54cad5ba.jpeg)