How to set the different left and right electrodes of transiesta？

Question

I am using transiesta, which works when the left and right electrode structures are consistent. Now I want to know how to set up the different left and right electrodes, how I should prepare the electrode input file and the input file of the whole system. The example under siesta/Test/TS/ the two ends seem to be the same right and left, while the three ends and four ends are not what I want, so it is difficult to understand how the different electrodes are set up. I'm really looking forward to a specific setup example or more detailed steps.

Answer 1

In the examples that you saw for 2 electrodes, the input files probably had a block like the following where you list the electrodes in your system:

%block TS.Elecs
  Left
  Right
%endblock TS.Elecs

Here Left and Right are the names of your electrodes. Then you have to go and individually define each of them. For example, to define the Right electrode:

%block TS.Elec.Right
  HS electrode.TSHS
  chemical-potential Right
  semi-inf-direction -a3
  electrode-position 1
  used-atoms 36
%endblock

If the Right and Left electrodes are the same, some parameters of the electrode definition, like HS (the hamiltonian file) or used-atoms (number of atoms in the electrode), will be the same. However the rest of parameters are different already. To define different electrodes you just need to specify these parameters accordingly. That is for example, for the Left electrode provide its hamiltonian file and the number of atoms that the Left electrode has.

To understand all the possible parameters find the TS.Elec key in SIESTA's manual (currently available here: https://www.siesta-project.org/SIESTA_MATERIAL/Docs/Manuals/siesta-4.1.5.pdf).

Preparing the input file for the calculation of the extra electrode is done exactly the same as you did for the first one.