[gpaw-users] dipole correction

[Misha Monder]

Thank you Ask.


I am calculating reaction energies for adsorption reactions as well as the vibrational frequencies for the adsorbed species.

I get an error if I try to 'restart' a structure that was solved using dipole correction.  

The command I use for activating dipole correction:
ps=PoissonSolver(nn=3)
calc = GPAW(xc='RPBE', ..., poissonsolver=DipoleCorrectionPoissonSolver(ps, 2), ...)

The output reports that the Poisson solver is using a '17 nearest neighbors central finite-difference stencil'.

This is with the release version GPAW 0.7.6383. Is the restart issue a known problem? 

Best regards,
Misha



----- Original Message ----
From: Ask Hjorth Larsen <askhl at fysik.dtu.dk>
To: Misha Monder <misha_monder at yahoo.com>
Cc: GPAW users <gpaw-users at listserv.fysik.dtu.dk>
Sent: Tue, June 8, 2010 5:36:33 AM
Subject: Re: [gpaw-users] dipole correction

Dear Misha

On Mon, 7 Jun 2010, Misha Monder wrote:

> Hello all,
> 
> Do I need to include dipole corrections (added to the 0.7 release version) for slab calculations that are not periodic in the z direction? I am assuming no because the erroneous electric field is introduced only when periodic boundaries are used. Am I correct in my understanding?
> 
> Thanks.
> 
> Cheers,
> 
> Misha


There's *supposed* to be an electric field around a dipole, and that field must have a step - this step is incompatible with periodic (clearly) boundary conditions, but also with the non-periodic ones in GPAW because they are *zero* boundary conditions.

Therefore dipole correction is always "necessary" to describe a dipole layer.  But it may not be particularly important, depending on which quantity you are interested in.

Regards
Ask