# Combining files from LigParGen

**URL:** <https://gromacs.bioexcel.eu/t/combining-files-from-ligpargen/1916>\
**Category:** User discussions\
**Tags:** forcefield\
**Created:** [April 7, 2021, 4:22pm UTC](https://gromacs.bioexcel.eu/t/combining-files-from-ligpargen/1916 "2021-04-07T16:22:29Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mdigennaro](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@mdigennaro](https://gromacs.bioexcel.eu/u/mdigennaro)\
**Post date:** [April 7, 2021, 4:22pm UTC](https://gromacs.bioexcel.eu/t/combining-files-from-ligpargen/1916/1 "2021-04-07T16:22:29Z")

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GROMACS version:2021.1  
GROMACS modification: No

Dear all,

I would like to apply the Lysozyme in Water tutorial from [Lysozyme in Water](http://www.mdtutorials.com/gmx/lysozyme/) to my own system (TFSI diluted in diglyme).  
I have for both systems the results from LigParGen, the top file being different.

I can put the box around the salt and solvate it successfully. On the contrary, when using gmx grompp, I get:

> Fatal error:  
> Syntax error - File TFSI.top, line 6  
> Last line read:  
> ‘[atomtypes]’  
> Invalid order for directive atomtypes

What is the system expected to find here?  
Comparing to the results from the tutorial it might be this:

> ; Include forcefield parameters  
> #include “oplsaa.ff/forcefield.itp”
> 
> [moleculetype]  
> ; Name nrexcl  
> Protein\_chain\_A 3

Could anyone give me a hint here?

Thank you

Best regards,  
MDG

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<div class="post-metadata">

**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:** [April 8, 2021, 12:58pm UTC](https://gromacs.bioexcel.eu/t/combining-files-from-ligpargen/1916/2 "2021-04-08T12:58:54Z")

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All force field parameters have to be defined before they can be invoked in a `[moleculetype]` definition. If you have multiple topologies that introduce `[atomtypes]`, then you need to combine these directives. See [Common errors when using GROMACS — GROMACS 2021.1 documentation](https://manual.gromacs.org/current/user-guide/run-time-errors.html#invalid-order-for-directive-xxx)