# How to apply electric field in input .mdp file?

**URL:** <https://gromacs.bioexcel.eu/t/how-to-apply-electric-field-in-input-mdp-file/10145>\
**Category:** User discussions\
**Tags:** forcefield\
**Created:** [September 12, 2024, 12:20pm UTC](https://gromacs.bioexcel.eu/t/how-to-apply-electric-field-in-input-mdp-file/10145 "2024-09-12T12:20:35Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![amartya386](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@amartya386](https://gromacs.bioexcel.eu/u/amartya386)\
**Post date:** [September 12, 2024, 12:20pm UTC](https://gromacs.bioexcel.eu/t/how-to-apply-electric-field-in-input-mdp-file/10145/1 "2024-09-12T12:20:35Z")

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GROMACS version: gmx\_mpi, VERSION 5.1.4  
GROMACS modification: Yes/No  
Here post your question  
we applied constant electric field of 0.99 V/nm along Z-axis , but we did not observe any ions separation in the system.

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**Author:** ![MagnusL](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/magnusl/32/2380_2.png) [@MagnusL](https://gromacs.bioexcel.eu/u/MagnusL)\
**Post date:** [September 13, 2024, 7:22am UTC](https://gromacs.bioexcel.eu/t/how-to-apply-electric-field-in-input-mdp-file/10145/2 "2024-09-13T07:22:38Z")

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Hi!  
It would be good to have some more information to be able to help you more. Could you describe the system you are simulating? What is the purpose/goal of the simulation? What `electric-field` settings do you use in the mdp file?

Have you read the [Electric fields - GROMACS 2024.3 documentation](https://manual.gromacs.org/current/reference-manual/special/electric-fields.html) part of the manual?