[Pw_forum] graphene's band gap

[Eric Germaneau]

Dear Mehmet and Hui Wang,

That's what I did.
 From my calculations the occupied and unoccupied bands touch only at K 
point.
I was just confused because the scf calculation does not output a zero gap.
I mean the line "highest occupied, lowest unoccupied level" shows two 
different values and I expected them to be equal.
So, it seems I did not too bad in fact.
But how to experimentally get a zero gap then?
Thanks,

                     Eric.

On 03/09/2011 07:02 AM, Mehmet Topsakal wrote:
> Dear Eric,
>
> In addition, if you select 18x18x1 kpoints, your mesh should include 
> both K and M points.
>
> But for a band-structure calculation, you should arrange a kpoints 
> list along special directions, such as from GAMMA-to-M-to-K-to-GAMMA, 
> and do a nscf calculation....
>
>
>
> On Wed, Mar 9, 2011 at 11:28 AM, xirainbow <nkxirainbow at gmail.com 
> <mailto:nkxirainbow at gmail.com>> wrote:
>
>     Dear Eric:
>     The occupied and unoccupied bands touch each other only at M
>     point(or K point, I forget it).
>     You must include this point in you k-mesh.
>     Furthermore, if you include spin-orbital coupling, the band gap
>     will be opened at this point.
>
>     On Thu, Mar 10, 2011 at 1:30 AM, Eric Germaneau
>     <germaneau at gucas.ac.cn <mailto:germaneau at gucas.ac.cn>> wrote:
>
>         Dear all,
>
>         I'm trying to compute graphene's band gap but get stuck.
>         From my understanding a scf calculation should provide the
>         same energy for the highest occupied and lowest occupied level
>         which means a zero gap.
>         I played with the number a kpoints a finally got a band gap of
>         0.57 which is not null.
>         The scf convergence looks good.
>         I'm not (yet) an expert in DFT calculation so may did
>         something wrong or misunderstood something here.
>         So, I wonder if someone has already successfully performed
>         such calculation.
>         I have attached my input file.
>         Thanks in advance,
>
>                                         Eric.
>
>         -- 
>         /Be the change you wish to see in the world
>         / — Mahatma Gandhi —
>
>         Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn>
>
>         College of Physical Sciences
>         Graduate University of Chinese Academy of Sciences
>         Yuquan Road 19A
>         Beijing 100049
>         China
>
>         /Please consider the environment before printing this email.
>         Considérez svp l'environnement avant d'imprimer cet email. /
>
>
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>
>
>     -- 
>     ____________________________________
>     Hui Wang
>     School of physics, Fudan University, Shanghai, China
>
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>
>
> -- 
>
> Mehmet Topsakal  (Ph.D. Student)
> UNAM-Institute of Materials Science and Nanotechnology.
> Bilkent University. 06800 Bilkent, Ankara/Turkey
> Tel: 0090 312 290 3527 ; Fax: 0090 312 266 4365
> http://www.researcherid.com/rid/A-5015-2010
>
>
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-- 
/Be the change you wish to see in the world
/ — Mahatma Gandhi —

Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn>

College of Physical Sciences
Graduate University of Chinese Academy of Sciences
Yuquan Road 19A
Beijing 100049
China

/Please consider the environment before printing this email.
Considérez svp l'environnement avant d'imprimer cet email. /

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