# Topol.top file not generating

**URL:** <https://gromacs.bioexcel.eu/t/topol-top-file-not-generating/9586>\
**Category:** User discussions\
**Tags:** forcefield, topology\
**Created:** [July 5, 2024, 8:06pm UTC](https://gromacs.bioexcel.eu/t/topol-top-file-not-generating/9586 "2024-07-05T20:06:29Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![VeronicaKruk](https://avatars.discourse-cdn.com/v4/letter/v/8797f3/32.png) [@VeronicaKruk](https://gromacs.bioexcel.eu/u/VeronicaKruk)\
**Post date:** [July 5, 2024, 8:06pm UTC](https://gromacs.bioexcel.eu/t/topol-top-file-not-generating/9586/1 "2024-07-05T20:06:29Z")

</div>

GROMACS version: gmx pdb2gmx, version 2020-rc1-MODIFIED  
GROMACS modification: Yes

While trying to generate the force field for LYSOZYME (AKI1) I am receiving the following error message:

Program: gmx pdb2gmx, version 2020-rc1-MODIFIED  
Source file: src\gromacs\utility\futil.cpp (line 442)

File input/output error:  
topol.top

How to fix this?

---

<div class="post-metadata">

**Author:** ![Karis](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@Karis](https://gromacs.bioexcel.eu/u/Karis)\
**Post date:** [July 7, 2024, 3:33pm UTC](https://gromacs.bioexcel.eu/t/topol-top-file-not-generating/9586/2 "2024-07-07T15:33:31Z")

</div>

Could you describe how you prepared the files and share the exact commands you used?