[Wien] PBE0 functional

[Rocquefelte]

Dear Anurag,

W2web is very good to learn how to use the code. So, I will propose to 
you to first solve this problem.
However, if you really want to learn Wien2k using the command line, you 
can do it (it was the way that we learned some times ago).

One possibility, could be to first generate a structure file that you 
will send to the wien-list. It will help us to indicate to you how to 
set up your calculation.

But I should insist, the more efficient approach will be to first solve 
the problem of the w2web interface, because it really helps to set up a 
calculation (particularly for beginners).

Regards

Xavier



Anurag Chaudhry a écrit :
> 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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>
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