[gpaw-users] How can the vacuum potential be found out

[Ask Hjorth Larsen]

Hi

On Mon, 16 Jan 2012, Georg Kastlunger wrote:

> Hello community,
>
> I would like to calculate some orbital energies relative to the vacuum
> potential (the average Hartree potential in the vacuum) of my cell.
> I have already searched through the tutorial pages, but i couldn't find
> out how I can find the value of the vacuum potential.
>
> My question now is: Does anyone know an implementation, which makes it
> possible to print out this potential?
> Or otherwise can the average of the Coulomb potential in the vacuum
> somehow be calculated in gpaw?
>
> Another very important point would be the reference energy and the units
> of the potential printed in the output.
>
> Thanks in advance to everyone!
> Georg

Well, the effective potential is stored here:

   calc.hamiltonian.vt_sG

This is indexed by spin and grid point, e.g. vt_sG[0, 43, 14, 23] is a 
number.

However if you use a non-periodic cell the boundary conditions are by 
default zero, meaning that the potential far away is exactly zero.

Regards
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