# transmission in transiesta

Asked by Ali Jafari on 2017-08-23

Hello,
I have a few questions :

1.i calculate the transmission for our structures by tbtrans but when plot them even though i set tbt.Emin and tbt.Emax [-10,10] but transmission range is between [-4,8] while fermi energy for sacttering.EIG is -5.9022 that it is out of range transmission .

2.why transmission for any of voltages is different each other? and which one of transmission of voltage should I use for my paper [zero volt or ...]?

3.why energy band gap for transmission isn't identical with DOS ?

4.how i get .AVTEIG in tbttrans's output?

thank you .
regards.

## Question information

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Siesta Edit question
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Solved by:
Nick Papior
Solved:
2017-09-05
Last query:
2017-09-05
2017-08-23
 Nick Papior (nickpapior) said on 2017-08-23: #1

First I suspect you are using the 4.0 version, Util/TBtrans (and not Util/TBtrans_rep).

0. I would recommend you to use TBtrans_rep, it provides additional features.

1. The flags for specifying the energy is TS.TBT.Emin/max (please see the manual for further details). Note that the electronic structure is shifted to the Fermi-level so E = 0 is equal to Ef.

2. That is not question we can answer, it depends on what and which features you are investigating. In any case if you plot the transmissions in a paper you should indicate the applied bias (even if it is zero).

3. This may be due to insufficient k-point sampling, and/or a wrong setup of the electrodes/scattering region.

4. LDOS is the spectral DOS from the left electrode, while RDOS is the spectral DOS from the right electrode. Again, E=0=Ef. They need not be the same, and typically are not the same. The total DOS is LDOS+RDOS. It is up to you what to show.

5. AVTEIG is only calculated if you request the calculation of eigenchannels (TS.TBT.NEigen, see manual).

 Ali Jafari (maj7293) said on 2017-08-23: #2

I understand most of the questions you answered, except few items :

about question3: kpoint for electrode is 1*1*19 and i set 1*1*58 for tbtrans ,is it correct or i increase it ??

How can I find the energy gap on case.AVTRANSE? Do I need to act like DOS?
Do I need to have a transmission gap supply with DOS for all voltages?

my dos and transmission is not identical each other while dos both of electrode and scattering is correct and match by studied papers.

best regards.

 Ali Jafari (maj7293) said on 2017-09-05: #3

Thanks Nick Papior, that solved my question.