# Problem in creating ligand topology

**URL:** <https://gromacs.bioexcel.eu/t/problem-in-creating-ligand-topology/2235>\
**Category:** User discussions\
**Created:** [May 27, 2021, 8:42pm UTC](https://gromacs.bioexcel.eu/t/problem-in-creating-ligand-topology/2235 "2021-05-27T20:42:39Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ankush8](https://avatars.discourse-cdn.com/v4/letter/a/3da27b/32.png) [@ankush8](https://gromacs.bioexcel.eu/u/ankush8)\
**Post date:** [May 27, 2021, 8:42pm UTC](https://gromacs.bioexcel.eu/t/problem-in-creating-ligand-topology/2235/1 "2021-05-27T20:42:39Z")

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GROMACS version: 2021  
GROMACS modification: Yes/No  
I uploaded a molecule in mol.2 format in cgenff and thn i got the output  
file in .str format. and now i am converting the .str which is in charmm  
format to gromacs format using the script cgenff\_charmm2gmx.py by the  
following command as:-

python cgenff\_charmm2gmx.py abc abc.str abc.mol2 charmm26-mar2021.ff

but i am getting the following error

python: can’t open file ‘cgenff\_charmm2gmx.py’: [Errno 2] No such file or directory

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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:** [May 28, 2021, 5:41pm UTC](https://gromacs.bioexcel.eu/t/problem-in-creating-ligand-topology/2235/2 "2021-05-28T17:41:03Z")

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You’re calling a script that doesn’t exist. Either it’s named something else or you’re in the wrong directory.