[Pw_forum] graphene's band gap

[Duy Le]

On Thu, Mar 10, 2011 at 9:52 AM, Eric Germaneau <germaneau at gucas.ac.cn> wrote:
> 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.
This was just explained by Mehmet. Check it again
> So, it seems I did not too bad in fact.
> But how to experimentally get a zero gap then?
> Thanks,
>
>                     Eric.
>

--------------------------------------------------
Duy Le
PhD Student
Department of Physics
University of Central Florida.

"Men don't need hand to do things"
> 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> 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>
>> 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
>>>
>>> College of Physical Sciences
>>> Graduate University of Chinese Academy of Sciences
>>> Yuquan Road 19A
>>> Beijing 100049
>>> China
>>>
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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
>
> 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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