[gmx-users] eelctric field

[Christian Blau]

Hello Amin,


When you apply an electric field during the simulation by setting the mdp parameters like E-x =... as you describe, 
nothing more happens than that each atom experiences an additional force that is "atom charge * field strength". The 
energy terms or virial (that then would relate to pressure coupling) are not influenced by this. If these terms differ 
between a simulation with electric field and one without, then only because the system as a whole responds to the 
applied electric field.

gmx potential on the other hand is an analysis tool that is per se unrelated on how you chose to apply an electric field 
during your simulation or not. However, when applying an electric field, you would expect a different result from an 
analysis with gmx potential than without electric field, because your system will respond to the applied electric field.


Best,

Christian

On 11/13/19 2:44 PM, Amin Rouy wrote:
> Hi,
>
> I am using gromacs 5.0.4. I apply a uniform electric field in x direction
> of my box (no walls),
> E-x= 1  10  0, and simulation runs without error.
> I notice that the values of electrostatic interactions I get from the
> simulation is the same as without the an electric field. Which is strange,
> but according to previous questions in the gromacs forum this is true:
> ''gmx potential only calculates the electric field and potential of the
> system. It does not take into account the applied field.''
>
> Now, my question is are the other quantities obtaining from gmx energy take
> into account field effect? e.g. pressure of the system.