[QE-users] Band Structure and DOS contradiction in doped graphene

[Ari P Seitsonen]

Dear B S Bhushan,

   To me it looks like

  1) QE/PWscf sets the Fermi level in the band gap, at some arbitrary 
energy just so that the number of electrons is conserved: It could be 
higher (but hardly lower). This is normal, as the energy position is not 
specifically defined so long as the number of electrons is correct (or, 
the Fermi level can be anywhere in the band gap just as it is far enough 
from the valence and conduction band edges)

  2) the program to calculate DOS does not realign the Fermi energy, so 
with the broadening there appears some intensity at the Fermi energy

   After you check that this is the correct assumption (for example that 
the occupation of all bands is either 0 or 1), you can manually 
shift the Fermi energy to mid-gap in the plots; or, some people do not 
show the Fermi energy at all in systems with gap but align the energy 
scale so that the top of the valence band ("valence band maximum", "VBM") 
is at zero.

   Which value of Fermi energy do you use actually, the one from the 
self-consistent or non-self-consistent calculation?

     Greetings from Sunny Paris,

        apsi

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   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
     Ecole Normale Supérieure (ENS), Département de Chimie, Paris
     Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935


On Mon, 21 May 2018, B S Bhushan wrote:

> Dear Experts,
> I am analyzing doped graphene using pbe functional.
> Where, I end up having contradictory DOS and Band structure.
> 
> The Band structure shows a small band gap at the fermi level, however, the DOS shows few states on the fermi level.
> 
> What should I call the system in such cases, metallic or semi-metallic or semi-conducting ???
> 
> or have I done something wrong ???
> 
> The link below contains the figures and input scripts used by me.
> https://drive.google.com/open?id=11Q7xfMGCHJDUlPK0amTnWO-y4R70ZQWj 
> 
> Please suggest.
> 
> 
> Sincerely,
> B S Bhushan,
> Ph.D Scholar,
> ABV- Indian Institute of Information Technology and Management, Gwalior.
> www.bsbhushan.com
> 
> 
>