[DFTB-Plus-User] Regarding Fermi energy

[Gabriele Penazzi]

Hi Kazuma,

the technique used by DFTB+ to calculate the Fermi level has been
already touched in the mailing list

https://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/2011/000684.html

Short story, I can't see from your transmission but I would guess the
Fermi level is close to a band edge. At 0K you can compensate the
deficiency described in the link above by setting it in the middle of
the gap, and as it is also described in the SCC section of this online
tutorial
http://www.dftb-plus.info/fileadmin/DFTB-Plus/public/tutorials/cecamhp/html/transport.html


Best,
Gabriele


On 01/19/2016 05:23 PM, u3129004 at edu.gifu-u.ac.jp wrote:
> Dear Dr. Gabriele,
> 
> Thank you very much for your early reply. After calculation of contacts, 
> I found that Fermi energy is -3.777471. 
> 
> So in this case, is the Fermi energy -3.777471?
> 
> However if the Fermi energy is -3.777471, it follows that this material 
> is not semiconductor.
> 
> Sincerely yours,
> Kazuma
> 
> 
> ----- Original Message -----
>> Dear Kazuma,
>>
>> in the transport calculation the Fermi level is not defined, because 
> the
>> system is not necessarily in equilibrium. The value 0.0 is just a
>> placeholder.
>>
>> In fact, you set yourself the Fermi level of the leads as input 
> quantity
>> in dtb_in.hsd.device.
>>
>>
>> On 01/19/2016 05:05 PM, u3129004 at edu.gifu-u.ac.jp wrote:
>>> Dear DFTB+ users,
>>>
>>> I calculated graphene nanoribbon using DFTB+NEGF (please refer to an 
>>> attached file). I checkd the position of Fermi energy by typing like 
>>> following:
>>>
>>> grep "Fermi energy" ./detailed.out
>>>
>>> However it was found that Fermi energy = 0.0 eV.
>>> I think this value is not true because in this case of graphene, 
> this 
>>> material should be semiconductor. 
>>>
>>> Please tell me how to know right Fermi energy.
>>>
>>> In addition, this is the first time I use DFTB+NEGF. So it is 
> possible 
>>> that I made mistakes in my input files. It would be very helpful if 
> you 
>>> could give me any advice.
>>>
>>> Thank you in advance,
>>> Kazuma
>>> ---------------------------------------------------
>>> Kazuma KIHIRA
>>> Environmental & Renewable Energy Systems Division
>>> Graduate School of Engineering, Gifu University
>>> E-mail:u3129004 at edu.gifu-u.ac.jp
>>> ---------------------------------------------------
>>>
>>>
>>>
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> 
>>>
>>
>> -- 
>> --
>> Dr. Gabriele Penazzi
>> BCCMS - University of Bremen
>>
>> http://www.bccms.uni-bremen.de/
>> http://sites.google.com/site/gabrielepenazzi/
>> phone: +49 (0) 421 218 62337
>> mobile: +49 (0) 151 19650383
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> 
>>
> 
> 
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-- 
--
Dr. Gabriele Penazzi
BCCMS - University of Bremen

http://www.bccms.uni-bremen.de/
http://sites.google.com/site/gabrielepenazzi/
phone: +49 (0) 421 218 62337
mobile: +49 (0) 151 19650383