[Pw_forum] band calculation:chosing a specific band

[Nicola Marzari]

Parwana HABIBI wrote:
> Dear all,
>
> I have a question about band calculation. I would like to calculate a 
> band structure for my system, which I can do. There is a surface state, 
> and I would like to study this particular state within the band 
> structure. Therefore, I need to chose the specific band concerning the 
> surface state. In PWSCF input file, there is only 'nbnd' tag that marks 
> the nuber of bands I want to calculate.
> How can I chose that band among the number of bands I'm calculating? I.E 
> among the nbnd number of bands, how can I only plot my concerned band?
>
> Thanks,
>   

Dear Parwana,

1) in the calculation, you need to include all the occupied bands (plus 
some, for a
metal). You cannot "calculate" only one band.

2) After you have finished a successful calculation, the plotting 
subroutines allow you
to choose which band you want to plot (the second, the seventh, etc...) 
at which k-point.

3) if your surface state is not isolated (i.e. if anywhere in the 
Brillouin zone it crosses other
bands), then you have no other choice than to "disentangle" it.
See e.g. this http://arxiv.org/abs/0910.1748 from the SIESTA group.



nicola

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Prof Nicola Marzari   Department of Materials Science and Engineering
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