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

[B S Bhushan]

Dear Dr. Apsi,

Thank you for the explanation.

I considered the Fermi energy value from Non-self consistent calculation
(NSCF).
As you say broadening is responsible for these few states on the fermi
energy, will it be helpful if I change the smearing type???
(Pardon me if the question is pointless, I am not yet very good with the
core physics stuff)

I have used m-v smearing for the calculations, what if I use the tetrahedra
or other smearing method...  will it be helpful to avoid this issue ??
Requesting your insight, please.


Sincerely,
B S Bhushan,
Ph.D Scholar,
ABV- Indian Institute of Information Technology and Management, Gwalior.
www.bsbhushan.com


On Tue, May 22, 2018 at 2:42 PM, Ari P Seitsonen <Ari.P.Seitsonen at iki.fi>
wrote:

>
> 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
>
> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=
> -=*=-=*=-=*=-=*=-
>   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-metall
>> ic 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
>>
>>
>>
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