[DFTB-Plus-User] R: Similar files give different results in DFTB-NGEF transportOnly calculations

Alessandro Pecchia pecchia at ing.uniroma2.it
Wed Sep 4 08:52:02 CEST 2019

Dear Amit,


I quickly checked your structure and found a problem. You made it almost right, but if you look at the atoms of contact 1 (121:240) you see that the first PL is the one placed far from the device region.

Therefore the interaction Hamiltonian is 0 and T(E)=0.

You have just to reverse the order of the first and second PL of contact 1. Contact 2 seems ok.


However, since all of this is a little annoying, please have a look at setupgeom described both in the manual as well as in the dftb+ tutorial (recipes).  


Thanks for using dftb+,


Alessandro Pecchia





Da: DFTB-Plus-User [mailto:dftb-plus-user-bounces at mailman.zfn.uni-bremen.de] Per conto di Amit Gupta
Inviato: martedì 3 settembre 2019 15:44
A: dftb-plus-user at mailman.zfn.uni-bremen.de
Oggetto: [DFTB-Plus-User] Similar files give different results in DFTB-NGEF transportOnly calculations


I picked the device_7.gen file from the examples and removed its hydrogens for an experiment I am running. It works fine and I am able to get the transmissions graph.

But when I created my own file from vmd, with almost exact same structure, I get almost zero transmission. Its quite perplexing to be honest. What am I doing wrong?


I am attaching a tar file with a minimum working example. to run any file, just comment out the 2-3 line in dftb_in.hsd file. Everything else remains the same.


Thank you

Attachment content:

device_7.gen file: dehydrogenated graphene ribbon from the provided DFTB+ example tutorial

pristine_2_aligned.gen file: my own graphene ribbon of same dimensions and structure

*.xyz: xyz files of above *.gen files

C-C.skf: SK file for graphene

dftb_in.hsd: dftb input file for running the example

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