[gpaw-users] Charged oxygen vacancy in periodic systems

[Ioannis Remediakis]

On 11/03/2015 09:15, Teemu Parviainen wrote:
> Hi all,
> I want to do calculations for charged oxygen vacancies in periodic
> systems (MgO surface). Does anyone have any experience what is the best
> way to do this with gpaw? I came across to a method called Virtual
> Crystal Approximation and if I understood correctly I have to change the
> nuclear number of all Mg atoms so that the overall change corresponds to
> the charge of the vacancy. Is this correct? How is this done in gpaw? Is
> it sufficient to just change the Z number in the PAW setup file or do I
> need to generate completely new one?
>
> Thanks in advance,
>
> -Teemu Parviainen, PhD student, Jyväskylä Finland
>
> --


Dear all,

I would like to ask a more general question: is it possible to use VCA 
(virtual crystal approximation) in GPAW?

This method is very efficient in alloys of atoms with similar sizes and 
same number of valence electrons, such as SiGe. Instead of using a large 
cell with Si and Ge atoms, you use a small cell with virtual "SiGe" atoms.

VCA is implemented in some codes, such as Espresso. If I understand 
correctly, the pseudopotential for the virtual atom is the average of 
the two pseudopotentials. But I do not know how one could do this in GPAW.

Any help would be appreciated. Thank you!

best regards,
Ioannis


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Ioannis N. Remediakis
Department of Materials Science and Technology
University Of Crete,  710 03 Heraklion, Greece
Tel: +30 2810 394250      Fax: +30 2810 394201
                 http://theory.materials.uoc.gr
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