# Amber 94 force field query

**URL:** <https://gromacs.bioexcel.eu/t/amber-94-force-field-query/5452>\
**Category:** User discussions\
**Tags:** forcefield\
**Created:** [December 19, 2022, 8:11am UTC](https://gromacs.bioexcel.eu/t/amber-94-force-field-query/5452 "2022-12-19T08:11:35Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Rudhra](https://avatars.discourse-cdn.com/v4/letter/r/958977/32.png) [@Rudhra](https://gromacs.bioexcel.eu/u/Rudhra)\
**Post date:** [December 19, 2022, 8:11am UTC](https://gromacs.bioexcel.eu/t/amber-94-force-field-query/5452/1 "2022-12-19T08:11:35Z")

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GROMACS version:  
GROMACS modification: Yes/No  
Here post your question  
Hello, All  
I have prepared my protein topology using the AMBER 94 force field and TIP3P water model. I need to prepare ligand topology. I am facing difficulties during ligand topology file preparation. I used Acype online server ([Acpype Server](https://www.bio2byte.be/acpype/)). I obtained one folder which has multiple files.

 ![Acype](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/1/16e6ccd2c440a8a6640244aae062bde4da850b3b.png)

I want to perform the Build the Complex step now. For that I need .ini file. There are two prm, itp files in that folder like ligand\_GMX\_OPLS.itp, ligand\_GMX.itp. There is no ini file for ligand also, but gro file is there for ligand.

Which parameter file (prm), topology (itp) should I consider for further analysis?