[gmx-users] How can I check external electric field was applied?

[Dan Gil]

Hi,

You guessed correctly - gmx potential only calculates the electric field
and potential of the system. It does not take into account the applied
field.

Are you using walls in your system? If so, are you using the 3DC correction
along with PME for Ewald summation? If you answered yes to both of these
question, you need to use Gromacs version 2016.4 and forwards - there has
been an important bug fix.

As long as your gmx grompp didn't return any warning or errors, I would
expect it to be valid. You can share your MDP file with us and that might
help.

Dan

On Fri, Feb 23, 2018 at 11:45 AM, 이연경 <koki0724 at naver.com> wrote:

>
> Dear Gromacs users,
>
> I’m testing a simple system that has one sodium ion and one chloide ion to
> check external electric field.
> ( Apply strong field along z axis, so I added the line of E_z = 1 10 0 to
> .mdp file. )
>
> After a short simulation, I used ‘gmx potential’ to check the field.
>
> But the result graphs of potential.xvg and field.xvg were different from
> my expectation.
>
> Although I applied 10v/nm along z axis, the electrostatic potential and
> electric field was not around 10V.
>
> Does ‘gmx potential’ calculate electric field and electrostatic potential
> including external force I applied, or just a system’s?
>
> If ‘gmx potential’ does not calculate including external forces, is there
> any method to check external field was correctly applied?
>
> Thanks for your time :)
>
>  YK Lee
>
>
>
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