[Wien] PBE0 functional

[Anurag Chaudhry]

Hello Xavier,

Thank you very much for your comments.  You are right.  I am trying to get a quantitative estimate of the 4f-VB gap for similar compounds like Ba, Sr halides or oxides.  And I am trying to find any experimental measurements as well.

I will be very much grateful for any help to setup the calculation since right now I do not have wein2web running and have to rely on running the code from command line.  Right now the way the code runs is completely new to me.

regards,
Anurag




________________________________
From: Rocquefelte <Xavier.Rocquefelte at cnrs-imn.fr>
To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
Sent: Wednesday, 5 November, 2008 23:02:22
Subject: Re: [Wien] PBE0 functional

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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