[Pw_forum] DOS at Ef

[Lorenzo Paulatto]

On Wed, 24 Mar 2010 13:31:24 +0100, Gabriele Sclauzero <sclauzer at sissa.it>  
wrote:
> the Fermi energy is printed only at the end of calculations for metals.  
> In the case of insulators it is not defined. You can take any energy in  
> the gap as reference value for
> the DOS plot.

I would add a small note on this: if for an insulator, or an isolated  
system, you specify a number of bands larger than the strict minimum  
(nelec/2) than you will get in output the LUMO and HOMO level. If you  
instead use the minimum number of bands than you can still get the HOMO,  
but you have to get it yourself from the bands printout, which can be a  
bit annoying but does not require any specific skill. Nevertheless, those  
number are good for isolated systems, not for insulator. The reason is  
that for an insulator you will probably use reciprocal-space grid with a  
small number of kpoints, hence the real HOMO and the real LUMO may as well  
be in point which is not in the grid. In order to have more accurate  
values you can do an NSCF calculation with a few more bands and many more  
kpoints.

regards


-- 
Lorenzo Paulatto

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