[Pw_forum] Not getting right Band structure

[Lorenzo Paulatto]

In data 28 luglio 2009 alle ore 11:54:14, Neel Singh  
<neelphysics at yahoo.in> ha scritto:
> means band gap at gamma = 0.3058-(-8.9833)=  8.2891
>  which is very large ??

Not necessarily, the offset of band in a periodic system is arbitrary. You  
need to know where you Fermi energy is, or which are the HOMO and LUMO of  
your system to find the gap.


> 2) In the output of SCF and Bands , the output file has 4 warnings

This a very frequently asked question, please see the corresponing entry  
in the manual:
http://www.pwscf.org/guide/2.1.2/html-node/node56.html
http://www.pwscf.org/guide/2.1.2/html-node/node57.html


> for this I have already increase the following quantities  in the   
> increments
> kinetic-energy cutoff     =      40.0000  Ry to 60
>      charge density cutoff     =     250.0000  Ry to 400
> But still the warnings are there.

It is not a big increment of the cutoff that will solve this problem, but  
a small increment or nr1, nr2 nr3

cheers, and good work

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Lorenzo Paulatto
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