[Wien] EFG + ETA calculation

[Peter Blaha]

The size should be big enough, at least for a first calculation.

Is the supercell nearly "cubic", i.e. similar length in all dimensions ?

Is there only one Ga site ?

How are the distances after relaxation ?
Would it correspond to a more or less axial symmetry or is x,y,z very 
different and eta=1 is to be expected ??

Cd at an interstitial site ? I'm not sure if a Cd2+ ion really wants to 
substitute Ga3+.
Is your cell metallic ?
Do you find an "inpurity" band ?


Am 03.02.2015 um 11:49 schrieb Marcelo Barbosa:
> Dear Prof Blaha,
>
> The biggest supercell I used for Ga2O3 was 1x3x2, which has 120 atoms.
> Then I changed one of the Ga atoms to Cd and relaxed the atomic positions.
>
> Since GGA+U or hybrids won’t affect the EFG and ETA in this case, do you think I should try bigger supercells?
>
> Thank you very much for your help,
> Marcelo
>
>> On 03/02/2015, at 06:43, Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote:
>>
>> No, I don't think that for this system GGA+U or hybrids are appropriate.
>>
>> Is your supercell large enough (~100 atoms) ??
>> Did you relax the atomic positions ??
>> Maybe the Cd sits in a different position ??
>>
>> Am 02.02.2015 um 20:09 schrieb Marcelo Barbosa:
>>> Dear all,
>>>
>>> I need to calculate the EFG and ETA in a Cd impurity in Ga2O3 but using the usual GGA method gives me an ETA near 1 when experimentally it is known to be between 0.0 and 0.1.
>>> I would like then to ask what is the best method to get good EFG and ETA values in such a case:
>>> - use GGA+U for the 3d orbitals of Ga and 4d orbitals of Cd?
>>> - use onsite-exact-exchange / hybrid functionals for those orbits?
>>> - use hybrid functionals for all electrons?
>>> or do you think these different options won’t change the ETA?
>>>
>>> Best regards,
>>> Marcelo Barbosa
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>>
>> --
>> Peter Blaha
>> Inst.Materials Chemistry
>> TU Vienna
>> Getreidemarkt 9
>> A-1060 Vienna
>> Austria
>> +43-1-5880115671
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-- 
Peter Blaha
Inst.Materials Chemistry
TU Vienna
Getreidemarkt 9
A-1060 Vienna
Austria
+43-1-5880115671