# How to use OPLS force filed for my P-L simulations

**URL:** <https://gromacs.bioexcel.eu/t/how-to-use-opls-force-filed-for-my-p-l-simulations/4723>\
**Category:** User discussions\
**Created:** [September 2, 2022, 6:22am UTC](https://gromacs.bioexcel.eu/t/how-to-use-opls-force-filed-for-my-p-l-simulations/4723 "2022-09-02T06:22:05Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Manish](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@Manish](https://gromacs.bioexcel.eu/u/Manish)\
**Post date:** [September 2, 2022, 6:22am UTC](https://gromacs.bioexcel.eu/t/how-to-use-opls-force-filed-for-my-p-l-simulations/4723/1 "2022-09-02T06:22:05Z")

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GROMACS version:  
GROMACS modification: Yes/No  
Here post your question  
I want to use OPLS force filed for my P-L simulations. Therefore as per the instructions in the gromacs tutorial the two files for topology generation need to be processed. But both the servers i.e. [Topolbuild], [TopolGen] and [LigParGen] are not working. Therefore, I request to provide complete steps to execute the OPLS FF with complete topology generation.  
Thanks in advance.