[Wien] PBE0 functional

[Rocquefelte]

Dear Anurag,

Using PBE0 you will be able to improve the treatment of the correlation 
of the f states of Eu, and you will have Eu2+ without any problem.
However, your question contains another parameter related to the band 
gap of the Ba2+ or Sr2+ halide parent compound. As you may expect, this 
band gap will be based on p states of the halide for the valence band 
and d states of Ba or Sr for the conduction band. This band gap will be 
underestimated using DFT. So as you can understand, by using PBE0 for 
the f states of Eu, you will "correctly" reproduce the f states 
separation, but not the band gap of the parent compound. So, what about 
the energy separation between the VB (halide p states) and the 4f states 
in the gap?

One possible answer is simply to say that this is not the purpose of DFT 
calculations. Rigorously, you cannot use such calculations for such 
purpose (excitation energies ...) because you are using a one-electron 
method, although when you use PBE0 (which is orbital-dependent but 
always one-electron approach).

Another answer could be to say that previous calculations shows that 
some tendencies could be obtained when comparing different materials. 
So, if you plan to use these calculations to have a qualitative idea of 
the evolution of the BV-4f separation for different systems it could be 
OK. Such an approach will be better if supported by experimental data 
for some of the materials you are considering (in order to validate your 
approach).

Regards

Xavier


Anurag Chaudhry a écrit :
> Hello,
>
> I am new user of WIEN2K and have a question about the PBE0 functional.
>
> I am interested in calculations of Europium doped compounds (Sr and Ba 
> halides) where the Eu2+ is substituted on an isovalent Ba2+ or Sr2+ 
> site.  A single dopant is embedded in a host matrix of about 50 
> atoms.  I would like to know how accurately can the functional 
> describe the position of the Eu 4f electrons (7 4f electrons in Eu2+) 
> in the bandgap specifically the valence band - 4f energy gap.  Any 
> comments regarding experiences with Eu2+ will be very helpful.
>
> I have just started to use the software (only 2 days back) it will 
> help me very much if someone can tell how to do such a calculation.
>
> thanks and regards,
> Anurag
>
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