# About the direction of the electric field added to the box

**URL:** https://gromacs.bioexcel.eu/t/about-the-direction-of-the-electric-field-added-to-the-box/8725
**Category:** User discussions
**Tags:** mdp-parameters
**Created:** [March 29, 2024, 3:34am UTC](https://gromacs.bioexcel.eu/t/about-the-direction-of-the-electric-field-added-to-the-box/8725 "2024-03-29T03:34:19Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![ok1](https://avatars.discourse-cdn.com/v4/letter/o/9d8465/32.png) [@ok1](https://gromacs.bioexcel.eu/u/ok1)
#### Post date: [March 29, 2024, 3:34am UTC](https://gromacs.bioexcel.eu/t/about-the-direction-of-the-electric-field-added-to-the-box/8725/1 "2024-03-29T03:34:19Z")

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Hi, I built a 4 \* 4 \* 4 box and wanted to add an electric field along the Z axis. What I understand from the"Electric-field-z = -0.01 0 0 0" in the MDP file is that this is the electric field from the bottom of the box to the top of the box. I would like to ask my understanding is correct? Thank you.  
 ![88769d1c02c6bc9717ad0003647836f9](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/4/48aeac811dae1211b350c8c186a28b88fd7cb172.png)