[Pw_forum] number of bands and degenerate states in supercell

[Gabriele Sclauzero]

Il giorno 11/mar/2011, alle ore 19.37, pari shok ha scritto:

> Hello,
> I have a question and I appreciate your help in advance.
> I am making a supercell by repeating a unit cell of SiC. Then, instead of 8 atom in a hexagonal structure, there are 72 atoms in a supercell.
> My question is about the number of bands. 
> Theoretically, the number of bands would be just the same for the unit cell (32 in this case)

Why 32? Since you have 8 atoms per cell, either Si or C, the number of electrons should be 4*8=32, so nbnd=16 should be sufficient (for collinear calculations).


> and even if you increase them in the input file, they should just have degeneracy and overlap. However, they are not.
> I was wondering how I can interpret the bands.

For this point, please refer to Duy Le's reply and perform a search about "band refolding" on the forum (or in any electronic structure book).


HTH

GS

> Yours
> P Shok
> UMD  
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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