# Charges and itp file

**URL:** <https://gromacs.bioexcel.eu/t/charges-and-itp-file/11089>\
**Category:** User discussions\
**Tags:** simulation-setup\
**Created:** [January 21, 2025, 2:27am UTC](https://gromacs.bioexcel.eu/t/charges-and-itp-file/11089 "2025-01-21T02:27:15Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![shristika](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@shristika](https://gromacs.bioexcel.eu/u/shristika)\
**Post date:** [January 21, 2025, 2:27am UTC](https://gromacs.bioexcel.eu/t/charges-and-itp-file/11089/1 "2025-01-21T02:27:15Z")

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GROMACS version:  
GROMACS modification: Yes/No

I am trying to create an itp file using the opls-aa forcefield parameters. After I got the atomtypes in the molecule, it has a charge. Am i required to neutralise this charge in the molecule? If so, how do I do that? Also, how do i simulate the various pH levels for the same molecule.