[DFTB-Plus-User] NEGF 12,0 Nanotube

[Michael Foster]

Hi Gabriele,

Thanks for the reply. As regards to the symmetry comment, I was expecting
the steps (at least the first couple) to the left and right of the Fermi
energy to be symmetric; I've seen several articles in the literature were
this is the case for the 12,0 nanotube (also no bandgap). However, I
believe the issue has to do with the structure as you suggested.
Originally, I just used a nanotube generator to create the nanotube; I did
not run an optimization. I have since optimized the unit cell using DFTB+
(MaxForceComponent = 1.0e-5) and the transmission curve is closer to what I
expected but I still predict a small bandgap. I'm sure the issue has to do
with the structure...

Mike

On Fri, Feb 27, 2015 at 11:37 PM, Gabriele Penazzi <penazzi at uni-bremen.de>
wrote:

>
>
>
> --
>
> 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 <+49%20(0)%20421%20218%209328>
> mobile: +49 (0) 151 19650383 <+49%20(0)%20151%2019650383>
> skype: gabriele.penazzi
> fax: +49 (0) 421 218 4764 <+49%20(0)%20421%20218%204764>
>
>
> On 28/feb/2015, at 06:02, MF <foster362 at gmail.com> wrote:
>
> Fixing a few big typos, sorry DFTB community, I was in a rush:
>
> I have been carrying out a few test NEGF calculations. I have been able to
> run several of the example calculations without a problem (i.e.
> nanoribbon); however, I'm having issues with a 12,0 nanotube. My
> transmission curve is not symmetric (not to mention it should be metallic,
> no gap)
>
>
> Ups, i was reading (10,0), ignore what i said in last mail about the gap.
> Still the electron hole symmetry argument holds.
>
> One of the reasons which can open a gap is distorsion in the lattice such
> as cnt deformation, wrong lattice vectors etc. I'll give it a look but
> meanwhile it can be a pointer what to look at.
>
> Best
> Gabriele
>
> as it should be for a 1D nanowire; I'm also having the same problem with a
> 5,5 nanotube (haven't tried any others). I'm hoping the problem has to do
> with my input file and/or structure but I can't seems to fix/find the
> problem. Attached is my input file, geometry and transmission curve. Any
> help would be greatly appropriated.
>
>
> Thanks in advance,
>
> Mike
>
>
> <image.png>
>
> <cnt_12-0.gen>
>
> <dftb_in.hsd>
>
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