[DFTB-Plus-User] CNT Gate Settings

[Gabriele Penazzi]

I understand you expect it semiconductor, but I don't understand why it 
should be n-type, isn't it intrinsic.

Anyway yes, there is a way to force doping in a virtual crystal 
approximation by increasing or decreasing the reference neutral 
occupation. This can be achieved in the new MPI version with the keyword 
CustomReferenceOcc or in the old serial version by hacking the SK files. 
The doping in the reference I sent you was realized in this way.

Note that in a non metallic system DFTB+ defines the Fermi level 
numerically somewhere in the gap, usually near a band edge, due to the 
way it is numerically defined. If I work with a semiconductor at room 
temperature I use to shift the Fermi level in the middle of the gap by 
hand.

The Fermi is 0 in the detailed.out after a device calculation because in 
an open boundary set up the total charge is not fixed, and a Fermi level 
for the whole system is not well defined out of equilibrium.

Best,
Gabriele

On 12/14/2015 09:47 PM, George D Kubas wrote:
>
> An 8,0 CNT in vacuum should be inherently n-type due to chirality , 
> but maybe I need to virtually dope the system to impose this in the 
> program? If so, please excuse my ignorance in this regards. The fermi 
> energy for the SWCNT contacts is 3.84 roughly when calculated, but 
> when the device file is run the fermi energy reads 0 in the 
> detailed.out. This may be the reason for some of my errors. I am going 
> to try the MPI version as well which I was just able to install.
>
>
> George D. Kubas
> Materials Science PhD. Candidate
> Youngstown State University
> gdkubas at student.ysu.edu
> (330) 261-2967
>
>
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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 9328
fax: +49 (0) 421 218 4764

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