[DFTB-Plus-User] Carbon nanotube in the dftb+ program

[Gabriele Penazzi]

Hi George,

there is some error in the setup. The unit cell of the CNT is 32 atoms, 
the contacts must be two identical layers. In your input file the 
contact has 160 atoms, corresponding to 5 unit cells. Clearly the two 
layers can not be two rigidly shifted layers because they'd need an even 
number of unit cells.

The code write out the lattice vector extracted for the contact when 
there's an error, you see there's some problem because it has a non zero 
component in the x direction.

There's a tiny fortran utility I sent in mailing list 
(https://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/2015/002008.html) 
which may help you, it is used to repeat a principal layer N times in a 
way which satisfies the ordering, see also the online tutorial.

Last, if you can compile it consider to use the MPI version, the input 
format has changed a bit and the MPI format contains the latest one 
which we'll try to support now on.

Best,
Gabriele


On 11/23/2015 11:42 PM, George D Kubas wrote:
>
> Hello,
>
>
> I am quite new to the program and am trying to set up an 8,0 cnt 
> geometry in a .gen file. When I run the dftb+ program on the source 
> contact file I keep getting the error "Contact 1 does not consist of 
> two rigidly shifted layers". I used 
> http://turin.nss.udel.edu/research/tubegenonline.html 
> <http://turin.nss.udel.edu/research/tubegenonline.html>to generate the 
> atomic positions in a Gaussian format and 13 cell units long. I 
> thought I set up the correct order of device, source layer closest to 
> device, source layer furthest, drain layer closest to the device, and 
> drain layer furthest. I assume my error lies in the self created .gen 
> file. Any help would be greatly appreciated. Thank you for your time.
>
>
> George
>
>
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