[gpaw-users] Problem with charged slabs

[Heine Anton Hansen]

Dear Jaime,

The charged periodic corrections were implemented for the GLLB and EXX
functionals and this feature is therefore not user friendly. The
correction used to be default.
However, it is more than a year ago since I worked on this, so I am not
sure if the behaviour has changed since then.

The line I mentioned is in the output file from the queue system - not the
regular gpaw text output. I am sorry this was not clear from my previous
mail.

Best Regards,
Heine

On Wed, March 24, 2010 12:08 pm, Jaime Gómez wrote:
>
>     Dear Heine,
>
> Thank you very much for your response.
>
> I have checked that my calculations are not corrected, as I can not find
> this line in my output. Could you please tell me wich tag do I have to use
> to add the correction?
>
> Thank you again for your help.
>
>
>    Best regards, Jaime.
>
>
> ________________________________________
> From: Heine Anton Hansen [hahansen at fysik.dtu.dk]
> Sent: Tuesday, March 23, 2010 5:22 AM
> To: Jaime Gómez
> Cc: gpaw-users at listserv.fysik.dtu.dk
> Subject: Re: [gpaw-users] Problem with charged slabs
>
> Hi Jaime,
>
> Charged periodic systems can only be handled by adding a compensating
> homogeneous background charge. This results in an error that scales as
> V^(-1/3), where V is the volume of the unit cell. The leading error may be
> removed by adjusting the average potential as described in
> J. Paier, R. Hirschl, M.Marsman, G. Kresse,  J. Chem. Phys. 122, 234102
> (2005). With this correction the error scales as V^(-1).
>
> In my experience the error is still large. However, sometimes it is
> possible to extrapolate the total energy to infinite volume. Maybe this is
> possible for your system also.
>
> To see if the correction above has been applied, look for the line
> "Calculating charged periodic..."
> in the output files.
>
> Maybe you will find it useful to look at the source code:
> https://trac.fysik.dtu.dk/projects/gpaw/browser/trunk/gpaw/poisson.py
> (line 116-183)
>
> Best Regards,
> Heine
>
>
>
> On Mon, March 15, 2010 5:50 pm, Jaime Gómez wrote:
>>
>>     Dear gpaw-users,
>>
>>     I've been employing GPAW for a few months now and  I have observed
>> the
>> following problem when attempting calculations with a charge. For
>> instance:
>>
>>          For Au(111) neutral slab I obtain an energy of E(Au) = -99.09
>> eV
>>          For the same Au(111) negatively charged slab (charge=-1) the
>> energy is E(Au-) = -96.49 eV.
>>
>>     so adding an electron to the slab is endothermic, +2.5 eV, however,
>> the energy released should be close to the workfunction value, -5.1
>> eV.
>>
>>     The cell contains 36 atoms, periodic boundary conditions in three
>> dimensions and probably a compensating background.
>>
>>
>>     Is there any way to obtain the correct total energy for charged
>> slabs?
>>     Where can I read about how the compensating charge is added?
>>
>>     Thank you very much,
>>
>>     Jaime Gómez-Díaz.
>>
>> _______________________________________________
>> gpaw-users mailing list
>> gpaw-users at listserv.fysik.dtu.dk
>> https://listserv.fysik.dtu.dk/mailman/listinfo/gpaw-users
>>
>
>
>