[Pw_forum] graphene's band gap

[Eric Germaneau]

Did you read what I said?
Got it.
By the way, I've just realized that I did not thank Mehmet and Hui Wang.


On 03/09/2011 08:57 PM, Duy Le wrote:
> 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
>>>>
>>>> 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
>>
>> 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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>>
>>
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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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