# Oscillatinf electric field

**URL:** <https://gromacs.bioexcel.eu/t/oscillatinf-electric-field/5888>\
**Category:** User discussions\
**Tags:** mdp-parameters\
**Created:** [February 28, 2023, 5:25am UTC](https://gromacs.bioexcel.eu/t/oscillatinf-electric-field/5888 "2023-02-28T05:25:23Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Muhriddin](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/muhriddin/32/2005_2.png) [@Muhriddin](https://gromacs.bioexcel.eu/u/Muhriddin)\
**Post date:** [February 28, 2023, 5:25am UTC](https://gromacs.bioexcel.eu/t/oscillatinf-electric-field/5888/1 "2023-02-28T05:25:23Z")

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GROMACS version:2022.03  
Hello dear gromacs users. I wanted to apply a unidirectional, oscillating electric field to a system consisting of the solvent and a protein molecule. According to the documentation E0, omega, t0 and sigma should be shown in this order in mdp and I have shown as follows:  
electric-field-x = 0 0 0 0  
electric-field-y = 0 0 0 0  
electric-field-z = 0.4 0.0015708 0 0  
Since there is no pulsed field, I indicated that sigma=0. But I couldn’t figure out what t0 means.  
Can I apply oscillating field to the system with my mdp parameters above? Or should I include t0 as wel?

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**Author:** ![Joe](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/joe/32/1322_2.png) [@Joe](https://gromacs.bioexcel.eu/u/Joe)\
**Post date:** [March 10, 2023, 9:19am UTC](https://gromacs.bioexcel.eu/t/oscillatinf-electric-field/5888/2 "2023-03-10T09:19:15Z")

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The t0 field represents the frequency that the potential is applied at maximum strength. See this equation in the docs [https://manual.gromacs.org/current/reference-manual/special/electric-fields.html#equation-eq-efield](https://manual.gromacs.org/current/reference-manual/special/electric-fields.html#equation-eq-efield)