[Wien] Supercell

[georg at chem.au.dk]

I'm no expert on these supercell calculations, but I guess the density of
k-points should be the same.
This means that if you you use 2000 k-points for generation (the number you type
in to kgen, not the number in the IBZ) then you'll need approx. 500 generating
k-points for a 2x2x1 supercell. However the actuall number in the IBZ may not
be lower than the original because your symmetry is also lower

 Georg

Quoting "Khuong P. Ong" <ongpk at ihpc.a-star.edu.sg>:

> Dear Prof. Peter Blaha and Georg,
> 
>   Many thanks for your help. Section 10.4 in new Wien2k userguide is really 
> useful. It helped me a lot.
> 
>   I have one more question: how big is the number of k-points for super
> cell?
> 
> The UG said that supercells require less k-points than the original small 
> cell. But how much is it?
> 
> Let suppose that in order to calculate precisely electronic structure of 
> one material we need 200 k-points. Now if we generate a super cell: 2x2x1, 
> 3x3x1, 4x4x1. Approximately how many k-points do we need?
> 
>   In case of small cell we can estimate this number of k-point by following 
> instruction in textbook " DFT and the family of..." by Dr Stefaan 
> Cottenier. But in case of big cell I'm afraid that I'm not able to proceed 
> such instruction. That is because one SCF- cycle takes some hours or even 
> more.
> 
>   Please advice me how to estimate number of k-points wisely.
> 
>   I'm grateful so much for helps.
> 
> Regards,
> Khuong
> 


-- 
Georg Madsen
Department of Chemistry
Aarhus University
DK-8000 Århus C
Denmark
tlf (+45) 89423885