[Pw_forum] (really silly) questions about DOS calculations

[Eduardo Ariel Menendez P]

Hello,
I want to calculate a density of states of a metal. Following example 08,
after de
SCF calculation I do a nscf calculation, with the option
    occupations = 'tetrahedra' ,
and afterward I ran dos.x.
THis is OK and the DOS looks nice. However,  is it the only possibility to
calculate the DOS?

I had tried first using
    occupations = 'smearing' ,
    degauss = 0.02 ,
    smearing = 'fermi-dirac'
in the nscf calculation, but running dos.x afterward gives out of
magnitude values for the DOS,like 1.0E+193, i.e. infinity.

Reading the source dos.f90 and the Doc file INPUT_PW let me somewhat
confused. Up today, I had thought that the tetrahedrom method  was only
for DOS calulation, and that
Fermi-Dirac smearing was the physically correct way to do SCF calculations
in metals, and also for the DOS.
However, in INPUT_PW one can read
               'tetrahedra' :  for metals and DOS calculation
My doubts in brief:

1) Can one use occupations='tetrahedra' for SCF calculation in metals?
2) Can one use occupations='smearing'+degauss+smearing='fermi-dirac' for a
DOS calculation? If yes, has someone met the '1.0E+193' problem?

Thanks

Eduardo A. Menendez Proupin
Department of Physics
Faculty of Science
University of Chile
Las Palmeras 3425
Ñuñoa, Santiago
Chile
Phone: 56+2+678 74 11
http://fisica.ciencias.uchile.cl/~emenendez/