[Wien] Problems of calculating the effective U and setting shift during the supercell procedure

[Peter Blaha]

Please note that this procedure is limited and gives only some estimate 
of U (usually a fairly large one).

NiO: No, you don't need a shift. This shift is for surfaces or when 
generating heterostructures.

Fe3Al: Why do you have 12 atoms ? Is this not an FCC structure and one 
f.u. is enough. There is no need to run Fe3Al in a P lattice which is 4 
times as large.

However, you can use supercell to generate from the FCC lattice a 
primitive cubic one (P) and a 1x1x1 supercell. This would contain 12 
atoms and is probably big enough.

Best regards

Peter Blaha


Dear WIEN2k experts and users,

> I am a beginner of WIEN2k. The version is WIEN2k_21.1. Now, I am 
> learning to calculate the effective U following the note “Calculating 
> the effective U in APW methods. NiO” by Georg K.H. Madsen and Pavel 
> Novak. I have two problems about this topic.
>
> One is about generating a supercell. I generated the NiO.struct as the 
> following: first get the NiO.cif from the external database, then by 
> cif2struct to generate NiO.struct. During the supercell procedure, I 
> set the numbers of xyz direction are all 2, but I am not sure how to 
> set the optional shift (I think in this case I should set the optional 
> shift are all 0?).
>
> The other problem is if a supercell is required when we calculate the 
> effective U. I am considering the material of Fe3Al, in which exist 12 
> Fe atoms. In this case, do I have to generate a supercell of Fe3Al to 
> calculate the effective U of Fe? Or could I set one of Fe atoms as an 
> impurity.
>
> Thank you for your reply in advance.
>
> Best regards,
>
> Yu
>
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-- 
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Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-158801165300
Email:peter.blaha at tuwien.ac.at           
WWW:http://www.imc.tuwien.ac.at       WIEN2k:http://www.wien2k.at
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