[DFTB-Plus-User] Different Fermi energy calculated by DFTB+NEGF and only DFTB+

[Enlong Liu]

Dear Bálint,

As for the Fermi level in NEGF calculation, the manual says that we need to
firstly calculate the contact part using 'Task = ContactHamiltonian{}', and
in this step there will be a detailed.out file containing Fermi energy,
which is what I mean. And the manual says that when doing SCC calculation
of the device part, i.e. 'Task = UploadContacts{}', the value of
'FermiLevel' should be taken from the contact calculations, i.e. the
detailed.out file. And this value is different from the DOS calculation to
the same contact structure.

By the way, the manual uses 'SetForAll {}' to input Fermi level since the
two contacts in the example are the same. But what if they have different
Fermi level?

Thanks!

Best regards,


2014-05-09 15:09 GMT+08:00 Bálint Aradi <balint.aradi at bccms.uni-bremen.de>:

> Dear Enlong,
>
> > In the transport calculation, I used DFTB+NEGF to calculate the contact
> > firstly, which is part of BNT at one end and the result is -10eV
> > approximately. But if I just calculate the DOS or band structure to the
> > same BNT part, the fermi energy is just -4eV. It is interesting since I
> > think all other parameters are the same, only the calculation situation
> > is different, one is just DFTB+ for DOS, the other includes NEGF to
> > calculate contact properties before doing transport calculation.
>
> I am somewhat confused, when you talk about the Fermi-level in the
> NEGF-calculations. This is an external parameter in those calculations.
> Do you "self-consistently" set the Fermi level, until the number of
> electrons is correct?
>
>   Best regards,
>
>   Bálint
>
> --
> Dr. Bálint Aradi
> Bremen Center for Computational Materials Science, University of Bremen
> http://www.bccms.uni-bremen.de/cms/people/b_aradi/
>
>
>
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>


-- 
Faculty of Engineering at K.U. Leuven
BIOTECH at TU Dresden
Email: liuenlong20 at gmail.com; enlong.liu at student.kuleuven.be;
enlong.liu at biotech.tu-dresden.de
Mobile Phone: +4917666191322
Mailing Address: Zi. 0108R, Budapester Straße 24, 01069, Dresden, Germany
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