[Pw_forum] (no subject)

[Giovanni Cantele]

yueqin at mail.ustc.edu.cn wrote:
> Hi,All.
>   I want to calculate the DOS of one metal system. In nscf step,the number of
> 'nbnd' can give very different plot of dos. How can I define nbnd? Is it can
> define it equal to nbnds (in scf)? I need you help ,thanks!
>  				
>
> ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡Y.Q. Wang
> ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡yueqin at mail.ustc.edu.cn
> ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡2007-10-04
>   

from espresso-3.2/examples/README
example08:
    This example shows how to use pw.x to calculate the DOS of Ni
    and how to plot the Fermi Surface using XCrysDen

If you have a look to the example08 directory, an example of a DOS 
calculation
is given, than can help you to understand how to do it.

The variable nbnd is, as far as I know, the same variable for both scf 
and nscf
calculation, with the only difference that in the nscf calculation you 
may want to
increase nbnd to see what happens with 'unoccupied' bands.

Of course, the larger nbnd, the wider the energy range your calculation 
will span.

Thus, unless something strange is happening with you input file, the 
reason why the DOS
changes with nbnd is just that you are sampling higher energy bands as 
you increase nbnd.
Of course, this should not affect the 'lower energy' part of the DOS.


Giovanni



-- 



Dr. Giovanni Cantele
Coherentia CNR-INFM and Dipartimento di Scienze Fisiche
Universita' di Napoli "Federico II"
Complesso Universitario di Monte S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
Phone: +39 081 676910
Fax:   +39 081 676346
E-mail: Giovanni.Cantele at na.infn.it
Web: http://people.na.infn.it/~cantele